Transmission Ideas?

[Thorne]

Do we have any ideas of other gear boxes that might suite this build well? I'm really hoping to reach supercar level performance as I've got a already nicely built subaru. (400awhp turned up). I've broken quite a few 5 speeds including STi-RA gears. I will say my RA-box help up through YEARS of drag racing and rally racing and me beating the tar out of the box.

I'm also currently setup as a RWD subaru and i'm pretty sure I broke a stock wrx rear and I know i've already chewed up a front diff on 16psi.

[jimgood]

Here we go again...

Do you really think you're going to have as much stress on the transmission when you remove 1200 lbs of mass?

[shinn497]

Actually I am curious what to do beyond 300Whp.MY research shows this is the limit of the WRX tranny. The Sti can handle more but I don't know if that will fit. Early reports said no but we will have to wait.

The consensus before was that if you are really worried about the tranny, and want to keep the WRX 5 speed, buy a set of PPG gears.

[Xusia]

Maybe Mendeola will make an aftermarket transaxle for all the HP nuts out there -- Like they did for the GTM. If they do, it will likely be a year or two (based on how long it took to produce for the GTM) before it materializes. You could always build it with ~300hp when available, and go crazy later!

[autostang]

I am curious about this too, not so much for the power issue, but for the feel of the transmission. My least favorite part about my WRX is how it feels to shift. In comparison to many cars out there it seems to me that it is very clunky feeling. Its by no means a deal breaker, but it would be great if there was something that felt a bit higher end.

[Thorne]

I am curious about this too, not so much for the power issue, but for the feel of the transmission. My least favorite part about my WRX is how it feels to shift. In comparison to many cars out there it seems to me that it is very clunky feeling. Its by no means a deal breaker, but it would be great if there was something that felt a bit higher end.

If you do all the proper upgrades to the car the car will shift quite nicely. I ran STI-RA gears for multiple years and they held up pretty good. I'm more concerned about the diff than the gears.

02early03 box : Max power I would safely run stock weight 280awhp (I snapped second @ 280)
04+ 5 speed 300-350awhp driven nicely
STi-RA V6 350-375awhp
STI 6speed 500+


I think the lower weight will keep the gears alive assuming you don't have a 02 gear box but the diff I'm just not sure of. Plus the WRX front diff is open.

[Oppenheimer]

You are going to build a mid-engined supercar, to go drag racing?

Won't the STi gearbox work for you? I know others have mentioned about how STi box not ideal for this car, the gearing, it might be too big to stick out the back, etc. Not cost effective, overkill, etc. But all those downsides seem to be targeted for street or road race use. For drag racing, who cares if you have to swap gear ratios, hack the body (or even some of the sub-frame if it came to that) to get it to fit. Is even the STi box not string enough for your needs?

[StatGSR]

I see no reason why a set of PPGs and an aftermarket diff in a wrx 5spd case would have any issues with any of your goals..... or just about anybody's goals for that matter...

stop worrying people, there are plenty of options out there....

[riptide motorsport]

oppenhiemers got a point!

[3000gttom]

lol at listing peak hp as a limit for a tranny, anyone who knows what they are talking about understands its all about the torque, i dont feel like doing a bunch of fbd's so lets just look at this in the simplest way possible

because f=ma

you can start by multiplying the max torque it handles on the wrx by (1220/818)

another factor is air resistance, and assuming the 818 has a lower coefficient of drag you can have more torque at higher speeds too,

also 2wd has less traction than awd so half of the abuse that the tranny would get from awd launching is taken away too

ill be very suprised if these cars have tranny issues

[Evan78]

What are the issues to be considered when selecting a transmission? I don't know much, but here's the items that come to my mind:


Axle alignment (fore/aft)
Transmission length (too long in rear?)
Axle splines (easy to solve with custom axles, right?)
Bolting up to engine (adapter plate should handle most situations, shouldn't it?)
Chassis mounting points
Clutch actuation
Shifter


How would the Porsche G50 fit? That's the standard solution for the GTM, right? How strong is it?

[Niburu]

blowing the budget guys
which is half the reason why this car will be a success

[Evan78]

Who's budget? Just because FFR has a stated goal for what is possible doesn't mean everyone is going to build to that budget.

[Oppenheimer]

Who's budget? Just because FFR has a stated goal for what is possible doesn't mean everyone is going to build to that budget.

I would think the GTM would be a better fit for those with big budget aspirations.

Yes, many 818's will go beyond the base FFR budget, but there is no escaping the fact that the point of the 818 is less cost. The most expensive 818 builds will hardly reach the cheapest GTM builds.

[Evan78]

Doesn't the GTM weigh around 2500 lbs? And the kit is $20k?

There are two reasons to build an 818 right there. Just because you can afford a GTM and a big dollar build, doesn't mean it's the best project for a given individual.

I thought this thread is about transmission options. Is it necessary to go over everyone's goals, budgets, etc in order to tell others that the 818 is not the "right" car for them? It is a kit car after all...

[BrandonDrums]

lol at listing peak hp as a limit for a tranny, anyone who knows what they are talking about understands its all about the torque, i dont feel like doing a bunch of fbd's so lets just look at this in the simplest way possible

because f=ma

you can start by multiplying the max torque it handles on the wrx by (1220/818)

another factor is air resistance, and assuming the 818 has a lower coefficient of drag you can have more torque at higher speeds too,

also 2wd has less traction than awd so half of the abuse that the tranny would get from awd launching is taken away too

ill be very suprised if these cars have tranny issues

I agree except I think it would be LESS torque experienced on the gears at high speeds. Less wind resistance means less force of drag working against the engine and transmission to sustain or gain speed.

My argument otherwise is exactly as yours and I imagine it would be about the same cost and far more ideal to source an aftermarket transaxle vs trying to convert an STI transmission, modifying the chassis and body to make it fit only to want to swap the final gear to make the gear ratios taller so you don't have to shift more frequently than a mosquito to hit speed.

I've been one of the biggest guys to speak AGAINST the STI tranny for the 818. To be clear, my argument is about the overall gear ratios rather than the gear ratio spacing of those ratios. You'll want tightly matched gear ratios to keep it in the more narrow powerband that comes from a turbocharged engine. The STI tranny is great, don't get me wrong. It's just a monster of an AWD transmission with weight, size and technology as a result of being for an AWD application.

I just think for the worth of an STI tranny and then the costs associated with making it work in this application to end up cruising down the highway in top gear pulling 3200 rpm is not going to be conducive to a well balanced driving experience. Honestly spend the money to upgrade a 5mt if you're worried about it or see about getting a full aftermarket box which will be stronger and more compact than even an STI trans.

[PhyrraM]

A few facts, without getting into the variables of turbo spool....

1) The engine makes the same amount to torque regardless of what car it is in.
2) The gear ratios are the same regardless of installation.

1 + 2 = 3

3) The torque applied to the gearset will be the same regardless of WRX or 818 installation.

Consider the following:

The amount of time that the torque is applied to the gearset is less because the 818 will accelerate to shiftpoint much faster than a WRX.

The wheels may spin reducung the peak torque on the gearset in lower gears more in the 818 than the AWD WRX.

100% of the vehicles torque will be sent through a shaft small enough to fit inside a tradional layshaft cluster.


Pick your reality from somewhere in this mess. I'll wait to see a few built 818s before making transmission judgements.

[BrandonDrums]

A few facts, without getting into the variables of turbo spool....

1) The engine makes the same amount to torque regardless of what car it is in.
2) The gear ratios are the same regardless of installation.

1 + 2 = 3

3) The torque applied to the gearset will be the same regardless of WRX or 818 installation.

Consider the following:

The amount of time that the torque is applied to the gearset is less because the 818 will accelerate to shiftpoint much faster than a WRX.

The wheels may spin reducung the peak torque on the gearset in lower gears more in the 818 than the AWD WRX.

100% of the vehicles torque will be sent through a shaft small enough to fit inside a tradional layshaft cluster.


Pick your reality from somewhere in this mess. I'll wait to see a few built 818s before making transmission judgements.

If that were true, there wouldn't be any guidelines for not using overdrive when towing in a pickup truck. More mass means more stress on the drivetrain and everything else. Reducing mass reduces stress and load on everything.

A good way to picture it mentally, is Imagine the 818 somehow weighed just 100 lbs. What do you think would happen then when all the power ran through the transmission? Now imagine the same engine and transmission installed on a fully loaded semi with the brakes on. WOT but the clutch slips before the wheels turn.

When a clutch goes bad, it starts slipping in higher gears vs lower gears, if you hooked the car up to a big honking U-haul trailer and tried to go up a hill, you'd expect the clutch to start slipping in a lower gear right? Is there suddenly more torque being applied from the engine than before? Yes actually, here's why.

When I was in Highschool Physics we did a basic experiment that applies to this particular debate. We hung up a piece of paper by a string from the ceiling and punched it with a piezo force meter or whatever taped to our fist to measure the force exerted on the piece of paper. Then we went down to the gym and carefully tried to punch with the same amount of force on one of those big punching bags and had the computer record that result to compare.

The force on the piece of paper barely registered despite all of our strength while the force recorded on the punching bag was magnitudes larger despite all of our concentration to punch with the same effort as we did on the paper. Newtons third law describes this phenomenon, every action has an equal and opposite reaction. The piece of paper was incapable of exerting the same amount of instantaneous force on our fist as the punching bag, it had so little inertia due to its low mass that it would accelerate faster than our fist was capable of traveling so the force was never fully exerted on the paper. The punching bag however stayed put long enough for us to exert as much force as we could muster with our fists.

Now, F=MA (force = mass times distance) as laid out in Newton's 2nd law might seem on the surface to negate the above scenario. However our arms, just as a engines are incapable of producing a force over an infinite distance, or change speed at an infinite rate. Therefore, the A in this equation can't adjust infinitely given the limitations of the input mechanism and F eventually decreases when mass decreases past a certain threshold. The arm is limited because it's connected to our body and we can't run that fast, the engine because of the mechanical limitations of handling rotational forces and the limited rate in which fuel burns within the combustion chamber. In order to get the engine to exert it's maximum torque, there must be something capable of exerting the same amount of force upon it. Torque is a force, Horsepower is simply torque over distance and time or force over distance and time. When the object the engine is moving is very lightweight, then you must use gears to decrease it's mechanical advantage so it can apply it's full torque on the rotational system through increasing the linear distance in which the object moves per rotation of the engine.

In a multi-component mechanical system such as a subaru drivetrain, there are actually hundreds of F=MA equations taking place. Each piston, rod, crank, valve, cam, flywheel, gear, diff etc has it's own mass and it's own mechanical dependency to another system. All of those dependencies aggregate to a resulting peak "A" or acceleration of the system. Absent of any resistant force aside from the mechanical system itself, the inertia of all the components and the limited speed in which gasoline can oxidize prevents the engine from immediately revving from idle to redline when you step on the gas pedal and also reduces the torque that can be applied at high RPM's. A good race engine like a Formula 1 engine makes very little torque compared to it's horsepower but can continue to apply that torque even at extremely high RPM's and can rapidly accelerate the rotational velocity of the engine because of more optimal mechanical dependencies.

So in an F1 or Race bike engine, the "A" has a much higher limit so the engine can apply much greater force on that piece of paper because it can actually keep up with it, meanwhile a big rig turbodiesel engine with the same peak horsepower as the F1 car can't apply the same force on a piece of paper given the same gear ratios as the F1 car. The gear ratios would have to increase tremendously which would reduce the torque applied at the wheels but dramatically increase the distance in which that torque can be applied. However, that also results in much higher stress on the gears. A race engine opts for revs vs torque because tremendous weight is saved in mechanical components due to the lower instantaneous torque experienced in the powertrain to achieve the same result.

Thusly, reducing the mass of a vehicle reduces the stress on the transmission given the mechanical drive-train and gear ratios remain constant. To achieve the same amount of instantaneous torque experienced by the mechanical components in a drivetrain when the mass is reduced, the gear ratios would have to increase proportionally with the decrease in vehicle weight.

Pick your reality indeed.

[RossLH]

1) The engine makes the same amount to torque regardless of what car it is in.
2) The gear ratios are the same regardless of installation.

1 + 2 = 3

3) The torque applied to the gearset will be the same regardless of WRX or 818 installation.

True, true, and also true. What you're not taking into account is the inertia on the output side and how that affects the impulse of shifting. Obviously a 3200lb car is more reluctant to change its velocity than an 1800lb car. Assuming both have identical clutch and flywheel setups, shifting is the same between the two, and there is no wheel spin, the 3200lb car (WRX) will have a MUCH larger impulse than that of the 1800lb car (818). Simply put, the 818 will be a whole lot easier on the WRX 5-speed than the WRX is.

Regardless of all that, I'll be calling up Andrewtech and having them build me a PPG dogbox. Necessary? Nope. Awesome? Entirely. Why? Because its my toy and I'll build it in excess if I want. And to reiterate, dogboxes are awesome.

[shinn497]

Brandom Drums you are making several physics mistakes, I don't have time to correct them, but I will when I can.

[Niburu]

I thought this thread is about transmission options. Is it necessary to go over everyone's goals, budgets, etc in order to tell others that the 818 is not the "right" car for them? It is a kit car after all...
Do you really wanna cut and reweld some of the main chassis components?
This is an engineered chassis, when you start hacking into it you're changing how it's going to perform, particularly in a wreck.

[Oppenheimer]

1) The engine makes the same amount to torque regardless of what car it is in.

I think Brandon did a thorough job of explaining why this is inaccurate. In the interest of exerting meaningless physical punishment against deceased equine I'll add my 2% of the smallest non-metallic US currency:

If you rev an engine in neutral, does it still make all its torque? When you run a car on a dyno, does it need to apply a load to perform the test?

Pedal a bike in a given gear at a given rpm with the back wheel off the ground. Now try the same thing out on the road. Torque can only be generated in response to load.

[bromikl]

Good luck keeping traction with two drive wheels at 300 Hp. I doubt the transmission will ever experience the max torque the motor capable of producing. If you're drag racing, you already know you need a PPG gearset.

[Evan78]

Do you really wanna cut and reweld some of the main chassis components?
This is an engineered chassis, when you start hacking into it you're changing how it's going to perform, particularly in a wreck.Chassis modification would not be desired, but if the benefits make it worthwhile, why not? Just because it was engineered for one transmission does not mean it can't be reengineered.

With that said, nobody mentioned that route. I don't think we have enough info on the chassis to know if/when that would be necessary.

[Niburu]

With that said, nobody mentioned that route. I don't think we have enough info on the chassis to know if/when that would be necessary.

that's one of the point I'm trying to get to
we don't know enough until FFR realeases the CAD files and/or tells us what'll fit
and what sort of specs they've designed to

[Evan78]

Lack of information hasn't stopped much speculation elsewhere, I'm not sure why this thread should be any different.

[BrandonDrums]

Brandom Drums you are making several physics mistakes, I don't have time to correct them, but I will when I can.

I might have but the principle is correct. Its been a long time since my Physics years so I might have not correctly explained the mathematics but the statement is true:

Reducing weight while keeping engine power and mechanical leverage constant reduces the stress on the drivetrain. If that weren't true then vehicles would not have a stated towing capacity period and Lotus would not be in business.

[skullandbones]

Maybe it would be helpful to start a new thread called "Transmission Ideas: Theoretical Approximations For Systems With Relations To Constant Mass Particle Physics But Excluding Special Relativity". At least, it would give you fair warning that the subject of "Transmission Ideas" might be broadly interpreted. This is meant light heartedly. So please take it that way. However, it does seem that often there are 818 threads that go on tangents and stay there instead of being brought back by someone in the discussion. In this discussion, there is really a great opportunity to discuss, for example, an existing gearbox that the 818 is engineered for with PPG gears (sorry haven't researched that yet). Another possibility is to look at boxes that might fit in the same area as the existing mechanicals. Are there adaptors or machinists that would be able to mate the transmission to the engine?

I don't think this is productive in general and it reflects on the forum by alienating many who would like to join the discussions or at least follow their progress for tidbits of information. IMO. WEK.

[PhyrraM]

Reducing weight while keeping engine power and mechanical leverage constant reduces the stress on the drivetrain.

The time is not constant. The reduced weight manifests itself as increased acceleration, not as reduced torque.

In any case, my actual point was to either be an early adopter and incur the expense (overbuild or break) or wait and see how many tranny actually pop. My secondary point is that Subaru never put more than about 130HP/140ish ft/pounds through a FWD/2wd version of this transmission, and that involves nothing to do with the actual gearset.

[RossLH]

In this discussion, there is really a great opportunity to discuss, for example, an existing gearbox that the 818 is engineered for with PPG gears (sorry haven't researched that yet).

PPG makes several gearsets that are designed specifically for the WRX 5-speed box. I plan on going all out with their straight cut dogbox.

[skullandbones]

Now that I know what they are, it sounds like the PPG solution may be "bullet proof" but it may be pretty radical for street applications but probably OK for track. There are disclaimers about how noisy it is so maybe it's like that sound you here when a dragster lets off at the end of the 1000 ft: wa wa wa wa wa wa!!! If you are able to insulate the cockpit maybe it wouldn't resonate too much. But I have had transmissions that sounded that bad and it drove me crazy.

Another thing about the transmission (transaxle) discussion is that the WRX is designed as a all wheel drive with the mechanicals being changed to rear wheel only from front drive. I see this as really a big deal from a design and engineering perspective. No matter that it works, there is no data to support the performance as a rear drive unit. From a known entity with all sorts of data to support it's performance, when you change it, all the data goes out the window. So nobody really knows how well the transmission will survive under the new "untested" conditions. I think the FFR prototype testing (mechanicals) will be as interesting as the body reveal. IMO, WEK.

[RossLH]

The straight cut gearboxes are very loud. The helical boxes really dont make much noise at all. I used to have a semi-helical gearset (MFactory short ratio) that made a rather significant whine, and to this day I miss it. I think its a great noise.

[Xusia]

Guys! Holy crap. Seriously.

Both engine torque and vehicle weight affect the transmission. A simple explanation:

In simplest terms, what causes parts to fail is stress (force). As in, when the forces applied to the part exceed that part's tolerance. Engine torque is NOT the only force acting on the transmission. In order to get the car moving (or make it move faster than it already is - i.e. accelerate), the engine must overcome any resistance to movement. The amount of resistance is DIRECTLY related to vehicle weight.

Now, a simple example: Consider how much torque & HP a transmission handle when it's not connected to anything (i.e. no axles, wheels, tires, nothing). Next consider how long you think the transmission in a bone stock Imprezza will last if towed a 20,000 lbs trailer all the time. If weight didn't matter, this shouldn't be a problem because the engine produces far less torque than the transmission is capable of handling. Common sense (or as I like to call it these days, UNCOMMON sense!) tells you this scenario would be a huge problem (if it were even possible).

The bottom line is that vehicle weight increases inertial resistance and is therefore a "force" that acts on the transmission (just like engine torque), and should to be taken into consideration. The 818 will weigh less than the donor vehicle, so if 300 hp is limit of the transmission in a WRX, it should be higher in the 818. By how much I have NO IDEA. I'll leave that the mathematicians!

[Evan78]

I'm sure everyone will agree that all else being equal, faster acceleration results in greater stress on a transmission, right?

I feel similar to PhyrraM - the same engine will result in similar transmission stress regardless of if the car is 2000 or 3000 lbs. The 2000 lb car will see the peak stress level for a shorter amount of time. The difference as I see it, is that shock loads will be reduced in the lighter weight vehicle.

[shinn497]

I'm sure everyone will agree that all else being equal, faster acceleration results in greater stress on a transmission, right?

I feel similar to PhyrraM - the same engine will result in similar transmission stress regardless of if the car is 2000 or 3000 lbs. The 2000 lb car will see the peak stress level for a shorter amount of time. The difference as I see it, is that shock loads will be reduced in the lighter weight vehicle.

Ummm you have a contradiction. First you say that greater accel = greater stress.

Then you say same engine = same stress regardless of weight

Then lighter vehicle = greater accel = less time = less stress

Your conclusion should be the same as exusia's.

Your first statement is wrong. Greater force causes failure. Acceleration is dependant on mass. If we lessen the mass, the acceleration increased, but the force remains the same.

out of all these arguments xusia's is the most correct.

[shinn497]

I want to add something that is confusing everyone.

Consider newton's 3rd law. Every action has an equal but opposite reaction.

If an engine acts on a gearbox they both feel the same force period. As long as the engine's power is constant, this will not change regardless of the weight of the car.

What the weight of the car will change is the time this torque is applied. Therein faster accel times = less load on the tranny.

The question is not if the tranny will experience less stress. It will. The question is if the tranny will break . What I'm (and I think most of us ) can not be certain about is how much force is neccessary and how long it will take. This is why impulse is important.(Impulse = force*time). It could be that tranny's are more resistant to impulse spikes...which would be good. Maybe not...

I think several people have said this in different ways and we're getting lost in the sauce. As someone that teaches physics for a living, this is not surprising.

[Oppenheimer]

Another thing about the transmission (transaxle) discussion is that the WRX is designed as a all wheel drive with the mechanicals being changed to rear wheel only from front drive. I see this as really a big deal from a design and engineering perspective. No matter that it works, there is no data to support the performance as a rear drive unit.

I believe there actually is already data on this. FFR is not inventing the idea of repurposing the AWD transaxle for 2WD. There are kits that convert the Subie transaxle to 2WD mode, and its expected FFR will use one of these commercailly available units in the kit (or fab their own, etc.) These can be used to covnert to FWD, or for creating a mid engine RWD car. FFR are not the first ones to do this with the Subie drivetrain. They are pioneering plenty of things with the 818, but this isn't one of them.

[skullandbones]

I stand corrected. Do you have any "vendors" that I could search that? I would like to check it out. In the meantime, I will see if I can find something. Thanks for the heads up. WEK.

[skullandbones]

Hey, I found one right away: "Bremar". I'll have to do some more reading. Thanks again, Oppenheimer. WEK.

[BrandonDrums]

Hey, I found one right away: "Bremar". I'll have to do some more reading. Thanks again, Oppenheimer. WEK.

Yeah, here's that kit http://www.bremarauto.com/products/subaru-2wd-conversion-kit/

8157
8158

I think there are a couple other vendors as well. However, I'm close to expecting that FFR will provide a piece as part of this kit weather it's 3rd party or if they just machine the part somehow in-house. That part will be needed to get the kit on the road and it won't be sold separately since FFR's motto is they give you everything you need with the kit.

It's just a sleeve and a plate, still some specific splines in there to work out but something that simple can be made for way cheap given the right vendor or tools.

[jimgood]

Hasn't this been discussed enough over on NASIOC? My God. They have an entire forum dedicated just to transmissions with 29,267 threads and 240,544 posts (and counting). Do we really have to clutter up this forum beating this dead horse?

And for the guys that are leaving the mass of the vehicle out of the equation, try this extreme analogy:
Park a fully loaded dump truck on level ground and leave it in neutral
Put a breaker bar on a lug on the right side of the truck
Apply force to the breaker bar until the truck moves

Now put that breaker bar on the axle nut of a child's tricycle
Apply force until the tricycle moves

Given, in this scenario, that you are the engine and the breaker bar is the transmission, which vehicle is more likely to break the breaker bar?

[skullandbones]

I like your analogy. Thinking of that tric, I can imagine how crazy some of those 818 launches will be like!!

I don't think you will get much traction on the NASIOC thing though. When I first heard about it, I thought they were talking about a racing association like SCCA. So not everyone comes from the same auto education and experience perspective. I took advice given me and did go there for some reference that the poster thought would be helpful. I think he even gave me the specific link. So you make a good point that the info is already out there but many don't want to dredge thru a lot of that stuff and some don't want to ever go there for one reason or another (culture, knowledge base, extraneous info, etc). I think some of the people on this forum want to create their own database for the subject material and create iterations that may be similar to what is there but not the same. IMO. WEK.

[bobzdar]

Hasn't this been discussed enough over on NASIOC? My God. They have an entire forum dedicated just to transmissions with 29,267 threads and 240,544 posts (and counting). Do we really have to clutter up this forum beating this dead horse?

And for the guys that are leaving the mass of the vehicle out of the equation, try this extreme analogy:
Park a fully loaded dump truck on level ground and leave it in neutral
Put a breaker bar on a lug on the right side of the truck
Apply force to the breaker bar until the truck moves

Now put that breaker bar on the axle nut of a child's tricycle
Apply force until the tricycle moves

Given, in this scenario, that you are the engine and the breaker bar is the transmission, which vehicle is more likely to break the breaker bar?

This completely depends on what the weak link of the transmission is. If it's 1st gear and you're spinning tires, yes your analogy holds up. If it's 4th or 5th gear (or the differential), your primary load will be the aero resistance and then weight is not that big of an influence, so trying to accelerate at 100mph in 4th gear pushing against that air, it won't matter if the car weighs 3500lbs or 2000lbs, the engine will be putting it's full force through the drivetrain at around the same resistance and 4th or 5th will go pop regardless of car weight. Most drivetrain components are rated for a certain torque load, they don't specify the weight of the vehicle because they can only handle so much force. The advantage to the 818 will be if in lower gears it doesn't have enough traction to break the trans, but if you manage to hook it up, it'll still go boom.

[StatGSR]

http://1.bp.blogspot.com/_vDnFIyZiQq4/TT-VwrvJ5RI/AAAAAAAAAS4/o3AA_eFCcM0/s1600/DoubleFacePalm.jpg

[PhyrraM]

MOTIVATIONAL POSTER!

This is now officially Nasioc. :(

[StatGSR]

your right, we should go back to arguing about things we don't understand.....:rolleyes:

[Evan78]

So, is the argument being made that an engine pulled from a WRX will make significantly less power when installed in an 818? If the answer is no, then I don't see how all of these attempts at simple explanations or analogies are applicable.

Work = Force x Distance (W=Fd)
Force = Mass x Acceleration (F=ma)

Substituting the force equation into the work equation yields:

Work = Mass x Acceleration x Distance

In other words, the work performed is the product of the mass (weight of vehicle), rate of acceleration, and the distance covered. Naturally, the work performed by the transmission is going to contribute to wearing out parts. Our conversation is centered around the mass portion, and of course there will be less wear if the mass is reduced and transmissions will last longer, all else being equal.

But another question is how much affect will the reduced mass have on the chances of a structural failure? The conversation here is mixing structural failure (catastrophic failure due to exceeding the strength of the transmission components) and failure due to wear (i.e. towing a heavy trailer). I think lack of clarity on this point is contributing to the differing viewpoints.

This single event failure is the point that I've always been thinking about throughout the conversation since it relates to peak power capability. My interpretation of everyone's comments has been that engine output is assumed to be constant, regardless of what chassis it's sitting in. If the engine output is considered variable, it should be clarified.

[Evan78]

Here's an interesting test of a couple dyno runs (source (http://www.allfordmustangs.com/forums/2011-mustang-gt-tech/285975-2011-mustang-gt-auto-changed-gears-lowered-dyno-results.html)):

365hp/361tq with dyno set to no load
383hp/378tq with dyno set to 50% load

[shinn497]

So, is the argument being made that an engine pulled from a WRX will make significantly less power when installed in an 818? If the answer is no, then I don't see how all of these attempts at simple explanations or analogies are applicable.

Work = Force x Distance (W=Fd)
Force = Mass x Acceleration (F=ma)

Substituting the force equation into the work equation yields:

Work = Mass x Acceleration x Distance

In other words, the work performed is the product of the mass (weight of vehicle), rate of acceleration, and the distance covered. Naturally, the work performed by the transmission is going to contribute to wearing out parts. Our conversation is centered around the mass portion, and of course there will be less wear if the mass is reduced and transmissions will last longer, all else being equal.

But another question is how much affect will the reduced mass have on the chances of a structural failure? The conversation here is mixing structural failure (catastrophic failure due to exceeding the strength of the transmission components) and failure due to wear (i.e. towing a heavy trailer). I think lack of clarity on this point is contributing to the differing viewpoints.

This single event failure is the point that I've always been thinking about throughout the conversation since it relates to peak power capability. My interpretation of everyone's comments has been that engine output is assumed to be constant, regardless of what chassis it's sitting in. If the engine output is considered variable, it should be clarified.

Evan you are oversimplifying things.

First I don't think anyone has stated that an engine being pulled from a wrx will make less power when put into the 818. IF that was true than no one would build lighter cars.

Second, you can't decrease mass while keeping everything else equal. IF the car weighs less, and the engine makes the same torque, it will accelerate faster. Thus the force equation will not change.

Third, you are using the SCIENTIFIC definition of work. It isn't so intuitive that this is what causes wear. I argue that metals and suspension components are prone to breaking under strain. This is how much they deform when given an applied force...and the force of the engine does not change given what its load is.

As said before, lighter mass cars cause the transmission to experience the same force for less time. It is the impulse that changes.

[Evan78]

First I don't think anyone has stated that an engine being pulled from a wrx will make less power when put into the 818. IF that was true than no one would build lighter cars. That is part of my point. The argument seems to be that somehow one side of the equation remains constant (the engine) but the transmission sees less stress because the car is lighter DESPITE the fact that the acceleration is greater.



Second, you can't decrease mass while keeping everything else equal. IF the car weighs less, and the engine makes the same torque, it will accelerate faster. Thus the force equation will not change.Who said the equation would change? Of course the equation doesn't change. I thought it was the clearest way to show that everything balances. If work and distance are constant and we are changing mass, rate of acceleration changes as well. Perhaps you're misunderstanding me when I added "all else being equal". I am using that the way it is always used, to imply that we are holding all other relevant variables constant. Naturally, if you have a balanced equation, changing one value requires changing at least one other.



Third, you are using the SCIENTIFIC definition of work. It isn't so intuitive that this is what causes wear. I argue that metals and suspension components are prone to breaking under strain. This is how much they deform when given an applied force...and the force of the engine does not change given what its load is.So if work does not cause wear, what does? Sitting at rest? Everything is prone to breaking under strain, I don't think you'll have to argue hard on that point. I even mentioned that in the last 2 paragraphs of my previous post.



As said before, lighter mass cars cause the transmission to experience the same force for less time. It is the impulse that changes.Yes, that is what PhyrraM said early in this thread that many people seem to disagree with. The peak force is the same regardless of the weight of the car, it is the duration of the force application that changes if both cars are accelerating to the same speed. If that peak force is greater than the transmission can handle, you get transmission failure in either chassis.

[Xusia]

Evan, In all seriousness, I'm very confused as to your point. I mean no disrespect when I say you've made a bunch of statements, but *I* can't find a cohesive point anywhere in them.

Also, the force coming OUT of the engine may be the same, but the force actually EXPERIENCED by the various transmission (and drive train) parts can vary because there are other forces acting on them, such as the inertial resistance of the vehicle, the traction of the tires, etc.

To illustrate: Why is a 2000 lbs. car easier for a human to push than a 6000 lbs. car? Because the extra weight increases inertial resistance. If the force being applied to push it is the same, acceleration will be faster for the 2000 lbs. car (duh). In order for the 2 cars to have the same acceleration, the force pushing the heavier car would have to be greater. I think we all know this intuitively, but it illustrates the formula in action.

So how does this relate the transmission? In the example above the "transmission" would be the human's shoes (they transfer the force being generated to the ground). Even though the force being generated by the human is the same, the shoes are under more stress pushing the heavier car. Again, I think we all know this to be the case intuitively.

What continues to confound me is why these concepts are seemingly so difficult when applied to an engine & transmission...

[Oppenheimer]

The load on trans is not just about lower weight of the car, its also about 2WD vs AWD. Tires can act like a fuse to prevent excess stress on the trans when they break loose. Albeit, a not very well regualted fuse (its not like you can count on the tires to always break loose at a set threshold that is just below that of trans damage).

Lighter car = less overall strain on trans (during times of accel from low speed to overcome inertia)
less grip (less because there is less weight pushing the tires down into the pavement, and because there are now only two tires that count) = less strain on trans (during times of accel from low speed where tires will be more likely to lose traction)

[2KWIK4U]

Also, the force coming OUT of the engine may be the same, but the force actually EXPERIENCED by the various transmission (and drive train) parts can vary because there are other forces acting on them, such as the inertial resistance of the vehicle, the traction of the tires, etc.

Great way to explain it,

[Evan78]

Here are a couple statements I think we can all agree on:

Less mass = easier to accelerate = less stress on transmission
greater acceleration = more stress on transmission

My question is how do you know that the reduction in stress due to the reduced vehicle mass is not offset by the increase in rate of acceleration?

[Xusia]

OK, got it. GREAT question, BTW! My instincts tell me the increased acceleration would have less impact on transmission stress than the lack of mass, but I'm not enough of a mathematician to back that up with numbers. Mechanical losses? The fact that acceleration is squared?? We've got a lot of engineering types on this forum. Someone should have a better answer!

[Arrowhead]

Wow, my head hurts. I did learn something though, I was wondering how it's converted to RWD so I see there is a simple kit available so that's good.

As far as all the other disscussion, I won't even attempt to engage other than my only thought is would it be wise to upgrade the drive axles? I mean all the power is now only split by two instead of four wheels.

[PhyrraM]

...... my only thought is would it be wise to upgrade the drive axles? ...

Years ago, when Subaru still sold FWD versions of thier cars in North America, they had basically the same transmission - but used larger diameter front half-shafts on FWD models. They had no more than 140 HP. Something to think about.

[skullandbones]

I think the 818 tranny will suffer from the same sort of threshold problem the t5 has in the roadster. Under 350 hp, it's OK. After that there is a grey area depending on many factors (setup). At 400+ there is a clear consensus that the t5 won't survive. So there will probably be the same kind of "grey area" for the 818 tanny. I believe we are already experiencing that in the discussion (hypothetical). When these projects start to hit the road and strips, a real answer will begin to sort itself out.

If you stay with a stock WRX, the tranny should work OK stock and if you plan on adding say 75 to 100 hp, then helical gears and upgraded half shafts and associated gear might be the way to go. WEK.

[Flamshackle]

I think the 818 tranny will suffer from the same sort of threshold problem the t5 has in the roadster...

...If you stay with a stock WRX, the tranny should work OK stock and if you plan on adding say 75 to 100 hp, then helical gears and upgraded half shafts and associated gear might be the way to go. WEK.

This ^^^^

Stock tranny will be fine with stock power output. high horse power examples will need high horsepower capable gear sets.

[Evan78]

I think the 818 tranny will suffer from the same sort of threshold problem the t5 has in the roadster. Under 350 hp, it's OK. After that there is a grey area depending on many factors (setup). At 400+ there is a clear consensus that the t5 won't survive. So there will probably be the same kind of "grey area" for the 818 tanny. I believe we are already experiencing that in the discussion (hypothetical). When these projects start to hit the road and strips, a real answer will begin to sort itself out.

If you stay with a stock WRX, the tranny should work OK stock and if you plan on adding say 75 to 100 hp, then helical gears and upgraded half shafts and associated gear might be the way to go. WEK.That's a great point, the 818 situation is the same as what they've experience - same components in a lighter chassis. Is there much discussion on that topic in this forum or do I need to head over to the old one?

[BrandonDrums]

Here are a couple statements I think we can all agree on:

Less mass = easier to accelerate = less stress on transmission
greater acceleration = more stress on transmission

My question is how do you know that the reduction in stress due to the reduced vehicle mass is not offset by the increase in rate of acceleration?

I think people get mixed up between power and force. Power is force distributed over time or distance. Torque is an instantaneous measure of a twisting force.

This is a difficult conversation in the case of the internal combustion engine as technically speaking, the engine doesn't provide a continual force but is rather driven by a series of pulses evened out by a flywheel. The force of those pulses are variable dependent on the rate of movement in that system. A car doesn't operate on thrust but rather mechanical force which have limits based on the speed relationships of all of those mechanisms.

A rocket however, uses thrust to move and the force being exerted by a rocket is not dependent on speed since it's a simple relationship between the rocket and the gasses being thrown behind it, the rocket doesn't need to have any mechanical systems rotate to match the speed in which it moves through space.

That's probably how people are thinking of this scenario since more classical physics remove friction and other mechanical limits to keep the mathematics principles pure. F=MA always remains true in the case of the motorcar and the case of the space rocket. The difference is the car makes force by applying it to the earth in which the car moves in relation to and the engine is mechanically dependent on that relationship. The rocket simply generates force against itself which has a net relationship regardless of speed.

[Xusia]

Good point Brandon. There is also the issue of wind resistance (a negative force acting against acceleration) - which I purposely omitted to avoid overly complicating the discussion - that would also apply while the vehicle is in motion, in addition to the mechanical relationship you mention.

[shinn497]

I think people get mixed up between power and force. Power is force distributed over time or distance. Torque is an instantaneous measure of a twisting force.

Power is NOT simply force measured over time or distance. Impulse is. Specifically it is the integral of the force function over a period of time.

Assume everything is constant as these would be integral equations if not. I am putting the differential equations in parenthesis).
Energy = Work = Force*distance (dEnergy = dWork = Force (distance)*ddistance)
Power = Energy/time = dE/dt
Impulse = Force*time (dImpulse = Force(time)dtime)

Power is a measurement of instantaneous ENERGY. I.E. it can be directly converted to heat. In a car the input power of the engine goes into the kinetic energy of the car + the loss due to the dirvetrain, rolling resistance, and drag.

Engine power = delta (mv^2)/2 + Paricidic lossess + Drag

In the above examble it is actually rather difficult to measure these paracidic losses furthermore it is even less intuitive to translate the input power of an engine towards the strain of the components. This is why it is better to work with torque and Force.

Also if you must know torque = rXF

Where r is the radius of your spinning object and F is the force at the edge. This is a vector equation. It can also be expressed as:

torque = Iw

With omega equaling the angular velocity and I being the rotational intertia.

torque is useful because it has the same value regardless of the size of the rotating object. If I measure 200 n*m of torque on a wheel of 15 inches it will not change for a wheel of 18 inches.

Agan as we've said time and time again. There is no reduction in force due to vehicle mass. And increased acceleration does not translate to more stress.

If you took an 818 and a wrx and accelerated them for the same amount of time , with the same applied engine torque, the transmissions would experience the exact same stressess. The 818 would end up at a much higher speed, but it would still be just as prone to breaking.

Similiarly if you were to run an 818 at a constant speed on its torque peak (whether it is at its top speed is dependant entirely the the shape of the torque curve), the weight will NOT save you . The transmision is still as prone to breaking as a heavier car in the same situation.

Wind resistance doesn't complicate the situation. It is not even based on vehicle weight be rather the drag coefficient and the cross sectional area. Thus the difference in the 818's top speed will depend mostly on its shape and engine power. This is why it won't have a 200mph top speed like a supercar, but super car acceleration.

[el_jefe]

As long as it's not a bug eye, I'm not going to be concerned with the trans until I am well over 450-500rwhp. Which is where a stock internal EJ is likely to come apart anyway. 90% of the 818's built will not come close to those numbers, and the ones that do will know what to do with the transmission.

[skullandbones]

Ican appreciate your fervor in defending a position but I fail to see how it proves anything specific except that you might be right (debating mode).

I believe I remember that in the force equation, mass and acceleration are inversely proportional. If that is so then I figured that the prototype 818 should have an approximate 38% increase in accelaration with stock engine, transaxle, etc. as compared to the donor (guessed at 2900 lbs).

In the same equation, I think force and acceleration are directly proportional so if you double the force you will double the acceleration. Unfortunately, a lot of people will apply too much f and instead of a they will get b (boom). WEK.

[el_jefe]

*shrugs* No one will be able to "prove" anything until they build a car, and even then since most of the parts will be from a used donor car, the baseline for proof will be suspect.

So instead I will stand by the practical aspect. I see 400hp AWD Subarus racing on stock transmissions all day long (except the previously mentioned bugeyes) with minimal problems that cant be attributed to driver abuse.

Less resistance on the driveline equals less chance for things to pop. I base this on practical experience again, I was building VW based sandrails back in the 80's (very similar to the 818, put an drivetrain in a super light chassis) and on years of building 4x4's. A great example comes from the 4x4 world, my CJ5 happened to use the same U-joints as a friend did in his muscle car. My 100ish hp jeep would go through them like candy, where his 400hp car would rarely need to replace them. Less load (rolling resistance on the street vs rock crawling and off roading) equals less abuse, despite the disparity in power.

The same thing will apply with the 818. In a WRX, the transmission has to deal with more than double the resistance than in the 818. Twice as much contact patch, and twice the weight. The major problem we will be dealing with is wheelspin. edited to add: And possibly wheelhop. I have no idea how subarus are with wheelhop, but it will grenade axles pretty quick as well.

And the final point from a practical standpoint: watch some drag racing. When do you see more drivetrain failures, at launch when the resistance is maximized, or halfway down the track when horsepower is?

[BrandonDrums]

torque is useful because it has the same value regardless of the size of the rotating object. If I measure 200 n*m of torque on a wheel of 15 inches it will not change for a wheel of 18 inches.

Here is where you're getting stuff completely wrong. That torque is constant at the point at which it's applied but if the diamater of the wheel changes that is recieving that torque, the force applied to the pavement is reduced.

That's why people put smaller wheels on their cars for autocross sometimes, it increases the torque at the expense of top end speed.

[skullandbones]

I would love to be at the prototype testing especially for the first launch. Field testing is still necessary no matter how much wind tunnel, supercomputer time, or other simulations you employee (not to diminish anything done in development so far). So if what you say regarding the VX and sandrail experience is transferable, the stock transaxle should work pretty well for most applications. It would be good to know (with calculations) where that line is crossed so you know when a more bulletproof trans is needed. Speaking of that, when discussing the Legacy and some other models does an upgraded trans mean a beefier tranaxle or just different such as gear ratios, etc? Thanks, WEK.

[shinn497]

Here is where you're getting stuff completely wrong. That torque is constant at the point at which it's applied but if the diamater of the wheel changes that is recieving that torque, the force applied to the pavement is reduced.

That's why people put smaller wheels on their cars for autocross sometimes, it increases the torque at the expense of top end speed.

I am not wrong.

Torque is a vector quantity. It cannot necessarily be applied at a specific point. If a wheel is turning. The torque is the same regardless of its diameter.

The torque at 10 inches is the same at 18 inches is the same at 3 million miles. However, for convenience, torque is expressed in the middle of the object and points perpendicular to the direction of rotation. The direction it points is determined by the right hand rule.

Force is not torque. They are separate quantities with different units. I.e. Torque = Newton*Meters (foot-ibs) Force = Newtons (ibs).

I should note that that statement makes no mention of the force. If you rate an engine you can have no knowledge of the gearing, driveshaft size, and final drive ratios. This is why it torque is advantageous. Of course this is also dependant on how its mounted.

Of course this is all semantics and not really related to the current discussion.

[jimgood]

A lot of talk for such a little problem. I brought up NASIOC because the solution for attaining a stronger WRX transmission has been solved many times over. If you're really worried about putting 250+ lbs/ft torque through the drive line mounted in your 818, then go find one of those solutions and be done with it. For all I know, the op works for one of those gear set vendors and is here merely to plant seeds (and you're very naive if you don't think this type of thing happens all the time on the internet).

[PhyrraM]

...... No one will be able to "prove" anything until (a few cars are built)......

Well said.

[PhyrraM]

.... the solution for attaining a stronger WRX transmission has been solved many times over. If you're really worried about putting 250+ lbs/ft torque through the drive line mounted in your 818, then go find one of those solutions and be done with it. .......

This will only apply if the weak point doesn't move when converted to 2WD.

The front diff, ring and pinion, pinion shaft, and possibly more never saw more then 130ish ft/lbs in an OEM 2WD transmission. All of those have not seen significant upgrades because they are usually seeing only 50% of total power.

That being said, I still feel that ANY year 5 speed will be fine in 95% of non-abused driving. Drop the clutch or "slam-shift" and all bets are off.

[BrandonDrums]

I am not wrong.

Torque is a vector quantity. It cannot necessarily be applied at a specific point. If a wheel is turning. The torque is the same regardless of its diameter.

The torque at 10 inches is the same at 18 inches is the same at 3 million miles. However, for convenience, torque is expressed in the middle of the object and points perpendicular to the direction of rotation. The direction it points is determined by the right hand rule.

Force is not torque. They are separate quantities with different units. I.e. Torque = Newton*Meters (foot-ibs) Force = Newtons (ibs).

I should note that that statement makes no mention of the force. If you rate an engine you can have no knowledge of the gearing, driveshaft size, and final drive ratios. This is why it torque is advantageous. Of course this is also dependant on how its mounted.

Of course this is all semantics and not really related to the current discussion.

http://en.wikipedia.org/wiki/Torque#Machine_torque

~Machine torque

Torque is part of the basic specification of an engine: the power output of an engine is expressed as its torque multiplied by its rotational speed of the axis. Internal-combustion engines produce useful torque only over a limited range of rotational speeds (typically from around 1,000–6,000 rpm for a small car). The varying torque output over that range can be measured with a dynamometer, and shown as a torque curve. The peak of that torque curve occurs somewhat below the overall power peak. The torque peak cannot, by definition, appear at higher rpm than the power peak.

Understanding the relationship between torque, power and engine speed is vital in automotive engineering, concerned as it is with transmitting power from the engine through the drive train to the wheels. Power is a function of torque and engine speed. The gearing of the drive train must be chosen appropriately to make the most of the motor's torque characteristics. Power at the drive wheels is equal to engine power less mechanical losses regardless of any gearing between the engine and drive wheels.
Steam engines and electric motors tend to produce maximum torque close to zero rpm, with the torque diminishing as rotational speed rises (due to increasing friction and other constraints). Reciprocating steam engines can start heavy loads from zero RPM without a clutch.

[RossLH]

Torque is a vector quantity. It cannot necessarily be applied at a specific point. If a wheel is turning. The torque is the same regardless of its diameter.

The torque at 10 inches is the same at 18 inches is the same at 3 million miles. However, for convenience, torque is expressed in the middle of the object and points perpendicular to the direction of rotation. The direction it points is determined by the right hand rule.

Force is not torque. They are separate quantities with different units. I.e. Torque = Newton*Meters (foot-ibs) Force = Newtons (ibs).

Torque is a rotating force. It is the result of applying a linear force at some distance from an axis. This concept can be approached from the other direction as well--a torque at an axis can be translated into a linear force some distance from said axis. For instance, if you have an axle supplying 200Nm to a wheel 2m in diameter, the linear force at the outside of the wheel is 100N. Now, say you replace that 2m wheel with a 1m wheel, the linear force at the edge of the wheel is now 200N (ignoring mass, friction, etc).

So while you are right in saying the torque will not increase when you use a smaller wheel, understand that the same amount of torque at the axle means a greater force on the ground.

[skullandbones]

A lot of talk for such a little problem. I brought up NASIOC because the solution for attaining a stronger WRX transmission has been solved many times over. If you're really worried about putting 250+ lbs/ft torque through the drive line mounted in your 818, then go find one of those solutions and be done with it. For all I know, the op works for one of those gear set vendors and is here merely to plant seeds (and you're very naive if you don't think this type of thing happens all the time on the internet).

Just for the sake of reeling this debate by a few back into the focus of the thread, could you mention one of those "solutions" that you have seen on NASIOC? I'm sure there are as many as there are vendors but are there some that are budget friendly that would still do the job for a modified engine? Thanks, WEK.

[RossLH]

In my experience (and backed up by some numbers I crunched a while ago), if you break a stock transmission and replace it with a budget friendly fix, you'll break that too. The budget friendly designs do not address the main issue at hand, that being the narrow, unsupported length of the main shaft that sits over the front diff. This one unfortunate design element allows the shaft to flex, pulling the input shaft away from the output shaft at 2nd gear. Without adding support to that area of the main shaft, the same thing will happen with an upgraded gear set. The not-so-budget-friendly builds do address the problem, which is why you don't hear as much about them breaking.

Having that said, for a budget build you could do Legacy GT or STi RA gears. A step above that will get you MFactory gears, and the best (as reflected by the price) replacement gears are PPG gears.

[skullandbones]

That's good to hear! Do the more expensive gear sets include that beefier input shaft? I would assume they do but not familiar with this technology. I think one person mentioned upgrading to a stronger case, as well. Thanks for answering my questions.

One reason I don't want to participate in the NASIOC forum at this time is that I really don't have the time to cover that much ground in the time I have available for surfing and researching. I probably will go there more after things begin to solidify and I have specifics that relate to the project/build. If a vendor is pfishing to get more business let them bring their discussion to this forum. Easier for all of us! Thanks, WEK.

[RossLH]

The case is not an issue. Whoever started the myth of the case flex deserves a hearty smack in the face.

Regardless, yes the more expensive gear sets do have beefier input shafts. The only gear set that I will recommend is a PPG gear set. Yes, they're a bit pricey, but there's a reason you dont hear much about them breaking.

[el_jefe]

MOTIVATIONAL POSTER!

This is now officially Nasioc. :(

I hope not.


I'm permabanned at NASIOC :p

[Oppenheimer]

All the discussion about if reduced mass has any effect on trans load all seem to be assumming that traction is constant. The rock and hard place that the trans is between is the motor supplying the torque and the tire/road interface that is applying the resistance. Should the tires lose grip, the trans doesn't feel the load. With only 2 wheels to drive through with less weight pushing them into the tarmac (albeit with more weight on them then most front engine RWD designs), there simply won't be as much traction.

The more power the more likely the trans will not hold up, yet the more likely that tires won't be able to hold traction. We simply don't know if there will be enough hookup, with what tires sizes/compounds, at what hp/torque numbers, to make trans weaknes an issue. This is why all these dicussions are as acedemic as they sound until we get real world expereince with the 818.

[skullandbones]

For those with a little less experience with the WRX gearbox idiosyncrosies, here is an interesting website. Here again, the recommendations suggest that changing gearsets solves a lot of problems.

http://www.turbomagazine.com/features/0305tur_subaru_wrx_gear_set/index.html

Thanks, WEK.

[skullandbones]

For those with a little less experience with the WRX gearbox idiosyncrosies, here is an interesting website. Here again, the recommendations suggest that changing gearsets solves a lot of problems.

http://www.turbomagazine.com/features/0305tur_subaru_wrx_gear_set/index.html

Thanks, WEK.

[jimgood]

Just for the sake of reeling this debate by a few back into the focus of the thread, could you mention one of those "solutions" that you have seen on NASIOC? I'm sure there are as many as there are vendors but are there some that are budget friendly that would still do the job for a modified engine? Thanks, WEK.




One reason I don't want to participate in the NASIOC forum at this time is that I really don't have the time to cover that much ground in the time I have available for surfing and researching. I probably will go there more after things begin to solidify and I have specifics that relate to the project/build. If a vendor is pfishing to get more business let them bring their discussion to this forum. Easier for all of us! Thanks, WEK.
Neither do I have the time...nor the inclination. As someone that is concerned about the strength of the transmission, it is incumbent upon you to do that research. Please input "wrx stronger gears input shaft" into Google and be enlightened.:)

As to which is best...you'll never get a straight answer to that question on the internet unless you can find the one of the few people that has actually tried more than one gearset behind the same engine output levels where one broke and the other didn't (yet). And that rather small population is probably at NASIOC. Phil of Element Tuning has been poking around this forum and he might be numbered among them.

[skullandbones]

Well Jimgood you are probably right about me having to "break down" and go to NASIOC for a lot of the available info. I followed your advice and looked up the key words you suggested. I spoke to a technician in Colorado about the WRX trans. He referred me to NASIOC, too! However, he was very willing to discuss the issues with the stock trans. His company "Flatiron Performance" has transitioned to a Subaru service center so they don't build the performance upgrades like they used to. He suggested a shop that specialized in that task. They are asking $2188 for a JDM RA gear set but then you have to have it built by a reputable company to install or there is no guarantee. I also saw a complete trans built for $3150 and core charge with the same gear set. That technician also suggested that you should pay attention to the rally drivers as they are the ones who really "work" the WRX the most. So I think the link I provided does reflect some weaknesses of the stock trans that racers have figured out from experience. I also saw a poll on NASIOC that favored (heavily) the above gear sets for modified applications.

It seems to me that people would be willing to discuss this sort of conversation about the stock or variants of the WRX. It's, at least, as interesting as going to school on theoretical physics issues and has some practical value in that it can give some people (who don't know) a better focus on how they will spend their available budget dollars for this project. I would probably go for an upgraded OEM donor like a Legacy at this point, instead of spending $3000+ on a performance trans. But that is because I would not be pushing the envelope like a lot of guys and would vote for a stock or only moderately modified engine. Hey, thanks for your insight. WEK.

[Xusia]

The above illustrates why my plan is to not go beyond stock STI power levels. To go much beyond that starts to get really expensive; both to get the power, and beef up other components...

[RossLH]

As to which is best...you'll never get a straight answer to that question on the internet unless you can find the one of the few people that has actually tried more than one gearset behind the same engine output levels where one broke and the other didn't (yet). And that rather small population is probably at NASIOC.

I have an unfortunate amount of experience breaking gearsets at multiple stages of power. Never did get PPG's, eventually just sucked it up and got a 6-speed. Ran the car into a pole before I got a chance to break the 6-speed. However, 6-speed talk really isn't helpful here.

Bottom line is if you break a stock set, chances are the same driving style at the same power is going to break a budget build just as fast, because as I said before the main issue isn't addressed, and is hardly band-aided.

[Rasmus]

I'd think the limiting factor in the 818 and bone stock 5 speed trans is going to be the tires. Even with a LSD (which I'm sure many of you will swap in) you won't be able to break the transmission before the tires let go. Sure there will be a few bone headed pedal dumpers who pop tranny after tranny by hammering the gear shift, dumping the clutch, and fat fingering the syncros. The rest of us will shift smooth because it doesn't upset the car.

But until you try to launch with warmed up 345/35ZR18 Hoosier A6's and a long *** 3.27:1 final drive (2005-2007 Legacy GT Auto FD) you'll be fine.

But let me just throw this out there. Subaru is rumored to be considering their CVT for upcoming WRX's. Light car with high hp = fast. CVT = Peak HP all the time = faster. No shifting = smooth = even faster

[Oppenheimer]

Exactly. The tires will be the fuse that lets go to protect the trans. Not the most reliable or predictable fuse, but for most (inside the bounds you describe above) it will 'blow' well safe of trans issues.

[BrandonDrums]

I'd think the limiting factor in the 818 and bone stock 5 speed trans is going to be the tires. Even with a LSD (which I'm sure many of you will swap in) you won't be able to break the transmission before the tires let go. Sure there will be a few bone headed pedal dumpers who pop tranny after tranny by hammering the gear shift, dumping the clutch, and fat fingering the syncros. The rest of us will shift smooth because it doesn't upset the car.

But until you try to launch with warmed up 345/35ZR18 Hoosier A6's and a long *** 3.27:1 final drive (2005-2007 Legacy GT Auto FD) you'll be fine.

But let me just throw this out there. Subaru is rumored to be considering their CVT for upcoming WRX's. Light car with high hp = fast. CVT = Peak HP all the time = faster. No shifting = smooth = even faster

Rumored but I doubt that will take place. Another reason why subaru had lowered the power output of their engines is because their CVT can't handle as much torque as the old AT tranny. A CVT would be kinda cool in a WRX but I imagine they'll use the 6mt or develop a automated single or dual clutch transmission for it if they were going to try something new.

The newest rumor is just as the WRX name has been split from the Impreza, Subaru is considering splitting the name STI name from the WRX. In this scenario, the WRX will be what the STI is today, the flagship Subaru AWD rally monster priced at 35-40k and perhaps marketed like the EVO with multiple trims and transmission options. Then the STI will be it's own car that is much higher performance and also much higher-end priced and built to compete with cars like the M3, Lexus ISF or the Audi S/RS4.

Here's essentially what started that rumor http://www.autoblog.com/2012/02/28/big-decisions-loom-for-next-subaru-wrx-this-week/

The other half of that rumor is STI will still be split from the WRX name as just a in-house tuner badge like it is in Japan. Subaru has promised 4 new models by 2016, somewhere I read that 3 of those 4 new models would be performance cars. BRZ, new non-impreza WRX and the STI being it's own car delivers all 3 new performance models technically speaking leaving just the hybrid to being on board.

http://www.autoblog.com/2011/07/07/subaru-promises-four-new-models-by-2016/

However, this report makes me thing the WRX and WRX-STI are here to stay just on a new platform as they are today. The 5mt could live on in the WRX due to this, I was hoping the 6mt would be standard in the wrx and the STI version would have a DCCD option or something.
http://www.autoblog.com/2011/12/08/next-gen-subaru-wrx-targeting-downsized-2-0-liter-four-thats-up/

All rumors and speculation though so we shall see! As for the 818, I am a little worried that I'll be more attracted to a smaller, lighter and more powerful WRX/STI over the 818. It could up being a monster if it's light enough...I mean look at this Motor Trend rendering for the new WRX if they brought back the coupe...

8362

The kicker would be if Subaru did offer a DCCD, if it was the size of the 5mt, 2wd convertible and offered as a crate unit, I might drop that in the 818 instead lol.

[riptide motorsport]

Will you guys please stop speaking japanese!!! I'm soooo confused:cool:

[Xusia]

That's a LOT of ifs... :D

[305mouse]

Subaru has a new car coming out this fall. It's called a KX or something.

[PhyrraM]

VX Crosstourer. It's an Impreza wagon derivative.

[Etos]

I think you all need to take a step or 2 back. 300hp in a heavy 3400 pound AWD is pretty good power even with the 24% AWD transmission lose(prox 75 ponies lost to the wheels). Now take that same 300hp in half that weight and make it 2WD reducing the transmission lose.

Do you guys really REALLY feel you need more then that? Cmon, take that step back and realize exactly how crazy you all sound arm chair mechanicing what tranny you'll need for a power level that would actually turn a car from fun to work just keeping it together both driving and mechanically.

You want a solid transmission for upto 400hp, get an 06+ WRX trans and replace the front diff. There's no need to go crazy with PPGs and etc. Getting 400hp is seriously no different then getting 700hp out of a corvette in PTWR. Anymore then that and it's just plain retarded and more for E-Peen awards.

I bet you guys the most FUN iteration of this car will be a much lower powered version. I personally am going destroked from 2.5 to 2.34, long rod and super high compression with about 8-10psi boost from a tiny turbo. Instant power everywhere, 9k RPM rev limit, most likely a specb transmission to keep up with the revs. Aiming for 250-300hp to the wheels which will be underpowered for what the engine can really handle but anymore and it becomes work, not FUN.

[Xusia]

Etos, while I agree with you (my power goal is the same, though I'll prob be taking a less expensive route), I also believe "to each, his own." If 300hp isn't enough for others, that's fine and doesn't impact me in any way. They should feel supported to build it any way they want (no matter how crazy that may seem to others)...

[Rasmus]

9k RPM rev limit
Stock crankshaft can't do that. Not because they'll break but the oiling passages are drilled funny on the OEM cranks and stop oiling the bearings due to inertia. Even if you run a high pressure/high volume oil pump.

Scat (and a few others) makes an aftermarket Subaru crank that doesen't suffer this issue.

[RossLH]

Do you guys really REALLY feel you need more then that?

I don't need 400+whp 818 more than any of us need an 818 in the first place. No matter how you look at it, its nothing more than a toy. You play with your toy the way you want to, and I'll be busy scaring the ever loving crap out of myself in mine.

[Nuul]

I'll be busy scaring the ever loving crap out of myself in mine.

Yup, and anyone foolish enough to sit in my passenger seat.

[Etos]

Stock crankshaft can't do that. Not because they'll break but the oiling passages are drilled funny on the OEM cranks and stop oiling the bearings due to inertia. Even if you run a high pressure/high volume oil pump.

Scat (and a few others) makes an aftermarket Subaru crank that doesen't suffer this issue.

You did read the destroked part right? Plus the factory cranks are good with the right mods which plenty of people do. Not new to subarus(owned one since 05) and by this august will have a 500hp destroked, bored out, fully built block with sleeves, cams, +1 valves, springs, retainers, ported, twinscroll, EFR turbo. Will be one hell of a track car.

The people who know the most about destroked/stroked subaru engines or subaru engines period is Dom from MPS and Micah from 3MI. No one knows more about subaru engines then these guys.

[Etos]

Etos, while I agree with you (my power goal is the same, though I'll prob be taking a less expensive route), I also believe "to each, his own." If 300hp isn't enough for others, that's fine and doesn't impact me in any way. They should feel supported to build it any way they want (no matter how crazy that may seem to others)...

I understand. I also bet 90% of the people arguing about this whole weight vs stress vs whatever will NOT be getting a 400hp 818. The other 10% will realize how over the top such a car will be once they get seat time in it. I understand the alure to having that kind of PTWR. I also have a 570hp turboed S2000, selling it this spring cause it's just not a fun car. Sure the straight line roll through the gears is crazy but it gets old fast. I'd rather have a 300hp 818 with the build I'm doing then this 570hp s2000 which is part of the reason I'm selling it to afford an 818.

[Rasmus]

You did read the destroked part right?
I did.

[RossLH]

The people who know the most about destroked/stroked subaru engines or subaru engines period is Dom from MPS and Micah from 3MI. No one knows more about subaru engines then these guys.

Right on. Micah is a great guy (not to mention a genius when it comes to building Subaru engines), he doesn't know it yet but he'll be building my engine when the time comes.:D

[Rasmus]

Micah = 3MI Racing = Homemade WRX(from NASIOC), correct?

[PhyrraM]

Micah = 3MI Racing = Homemade WRX(from NASIOC), correct?

Correct.

[Thorne]

Right on. Micah is a great guy (not to mention a genius when it comes to building Subaru engines), he doesn't know it yet but he'll be building my engine when the time comes.:D

The other thing to consider is that your 818 is going to have a open diff :\.


I wish i could come up with a better trans solution because i really wanted to build one of these but alass I'm selling my donor

[RossLH]

It most certainly will not, especially not with the power I'm looking to make. PPG makes a torsen front diff that'll go real nicely with the dogbox I plan on having built.

....and so what if my transmission will cost damn near as much as the kit itself?:D

[metalmaker12]

02 wrx suspension (spindles, control arms, etc)with whit line bushings :check
06 sti brembo brakes: check
06 sti steering rack:check
02 wrx tranny with front LSD: check
All other needed components from 02 wrx: check
06 wrx motor with new timing belt and tune up:check
Cobb access port: check

The $&@&$&$&$& kit ...................hopefully soon

[Thorne]

02 wrx suspension (spindles, control arms, etc)with whit line bushings :check
06 sti brembo brakes: check
06 sti steering rack:check
02 wrx tranny with front LSD: check
All other needed components from 02 wrx: check
06 wrx motor with new timing belt and tune up:check
Cobb access port: check

The $&@&$&$&$& kit ...................hopefully soon
What front LSD are you talking about? the 02 transmission is made of glass and it does not have a front LSD by default.

[StatGSR]

you can still purchase and install them dude....... you seem to getting all worked up about this open diff non issue....

[Thorne]

you can still purchase and install them dude....... you seem to getting all worked up about this open diff non issue.... I'm aware you can install them. I'm more curios which one there looking at.

[fritts]

I haven't seen a conversion bell housing for it but what about a Porsche Boxster/Caymen 6 sp. Not an incredibly long transmission but is fairly large in size.

[StatGSR]

^ im pretty sure that transmission is backwards....

[fritts]

whoops..... not a Porsche guy

[PhyrraM]

Unless the Porsche engine turns backwards, the (midengined) Boxster and Cayman should have trannies with very similar layout to the Subaru ones (once converted to 2WD).

[Evan78]

Here's an EJ motor bolted to (http://www.precisionchassisworks.com/boxstersubaru-engine-conversion.html) what I assume is a Boxster transmission from Precision Chassis Works.

Click link for large images and more details.

[StatGSR]

Unless the Porsche engine turns backwards, the (midengined) Boxster and Cayman should have trannies with very similar layout to the Subaru ones (once converted to 2WD).

oops, i was thinking they were RRs

[bugeye_fever]

Well most of them are, lol. No worries. I'm curious to see how the Subie front ring and pinion will hold up at high power levels. Probably a non issue, but i think we've beat the gearset dead horse long enough. Now i've never heard of any failures, but this is the one part of the trans that will see double the stress than it did in a wrx no matter what the power level of the donor was.

[wjfawb0]

I'll never run a car on a track, because I don't want to afford wadding it up and walking away from it. Taking curves on public roads too quickly can be bad news as well. About the only thing I can regularly enjoy in a toy street car is the acceleration. I think that's what I liked least about my STIs. The turbo lag made them less exciting as street cars compared to a roots supercharged cobra mustang. Once the 818 is released with details I'll be investigating what it would take to build one with a broad torque curve and reliable transmission with a limited slip diff. Turning over both rear wheels will be more important to me than how many Gs it can achieve in a corner.

[Exidous]

Edit: Ugh disregard. Old post.
A few facts, without getting into the variables of turbo spool....

1) The engine makes the same amount to torque regardless of what car it is in.
2) The gear ratios are the same regardless of installation.

1 + 2 = 3

3) The torque applied to the gearset will be the same regardless of WRX or 818 installation.




This is drastically oversimplified. Put a subie with 350wtq on a lift and bang through the gears. I'd bet they don't break. Now put the subie on the ground and do the same. Weight matters. Going from 3400lbs to 1800lbs and awd to rwd will reduce stress on the transmission.

Force=mass*accel

The force on the trans gears is directly related to the mass of the vehicle.

[Evan78]

Edit: Ugh disregard. Old post.


This is drastically oversimplified. Put a subie with 350wtq on a lift and bang through the gears. I'd bet they don't break. Now put the subie on the ground and do the same. Weight matters. Going from 3400lbs to 1800lbs and awd to rwd will reduce stress on the transmission.

Force=mass*accel

The force on the trans gears is directly related to the mass of the vehicle.Are we supposed to disregard because you don't believe what you said or just because the post is old? :D

[Exidous]

The latter. :p

[Evan78]

Well, in that case, you are saying that mass is decreasing, so the force must be decreasing also. What's going with acceleration?

[BrandonDrums]

Well, in that case, you are saying that mass is decreasing, so the force must be decreasing also. What's going with acceleration?



Oh dear, this convo again.

Best way to test it yourself: Try punching different objects with the exact same amount of effort from your arm. First punch a piece of paper held suspended in front of you, then punch your car. Feel the difference?

So does your engine and transmission. With the same throttle input but on a 1800 lb car the stress on the drivetrain is far less than on a 3300 lb car.

Why? Objects that apply dynamic force can only apply that force over a limited distance at a limited maximum rate and limited maximum change in speed. If the object being acted on requires less force to surpass the maximum acceleration and rotational velocity of the engine, then only the force required to achieve that acceleration is applied despite the higher potential for the engine/fist to apply an instantaneous force.

So a 500hp engine with 500tq simply can not apply all 500 of it's torque to a piece of paper duct taped to the outputshaft, for example.

That's why gears exist.

If you want to get more scientific about it, it's Newton's third law of motion 'every action sees an equal and opposite reaction'

Because of this, it's not the max output of your fist or engine that determines the force being applied, it's the amount of force the object being acted on is capable of also exerting back on the engine or your fist that limits the stresses seen in the system.

End of story.

[csdilligaf]

So is this correct in thinking?

The JDM STI 6sp is heavier and longer may stick out the back alittle but has stronger close ratio gearset?
I can live with all of that. So with all the EJxxx versionxxxx how do I tell which is what?
I would plan on something like this EJ20 version 7
http://www.ebay.com/itm/JDM-SUBARU-EJ20-T-6-SPEED-TRANSMISSION-STI-IMPREZA-6SPEED-TRANSMISSION-GDB-STI-/270965945951?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f16d4365f&vxp=mtr
What year would this be? I understand that 1st gear will be real low but I rather like that idea. I like to keep busy shifting.
With the STI speed I use this center diff lock kit I think?
http://www.possumbourne.co.nz/trans_diff_parts.html
Are my assumptions correct?
I would follow this Matrix build and use the 2WD conversion he used.

[Etos]

Oh dear, this convo again.

Best way to test it yourself: Try punching different objects with the exact same amount of effort from your arm. First punch a piece of paper held suspended in front of you, then punch your car. Feel the difference?

So does your engine and transmission. With the same throttle input but on a 1800 lb car the stress on the drivetrain is far less than on a 3300 lb car.

Why? Objects that apply dynamic force can only apply that force over a limited distance at a limited maximum rate and limited maximum change in speed. If the object being acted on requires less force to surpass the maximum acceleration and rotational velocity of the engine, then only the force required to achieve that acceleration is applied despite the higher potential for the engine/fist to apply an instantaneous force.

So a 500hp engine with 500tq simply can not apply all 500 of it's torque to a piece of paper duct taped to the outputshaft, for example.

That's why gears exist.

If you want to get more scientific about it, it's Newton's third law of motion 'every action sees an equal and opposite reaction'

Because of this, it's not the max output of your fist or engine that determines the force being applied, it's the amount of force the object being acted on is capable of also exerting back on the engine or your fist that limits the stresses seen in the system.

End of story.

Tq is Tq. It doesn't care how much the object weighs. If it weighs little, it'll just move along faster in a shorter amount of time.

The only time the stress differs is from a stop and even then it's not so much about AWD/RWD but the amount of rubber on the road. A 225 tire for instance in a RWD setup is 550mm of rubber resisting movement. In AWD that becomes a whopping 1100mm of rubber. If you dumped the clutch on a RWD car with 550mm tires, it would have the same exact amount of stress as 225mm AWD tire setup.

Your analogy of punching things doesn't work either. You're methods are so way off it's not even in the same sport. The above explains why from a stop about the AWD/RWD difference in stress. When in movement it's just very simple. A lighter car with 300tq will just move along faster then a heavier car with 300tq. Weight has no affect on the stress, it just allows the car to move faster. It isn't that hard to understand.

[SkiRideDrive]

Tq is Tq. It doesn't care how much the object weighs. If it weighs little, it'll just move along faster in a shorter amount of time.

The only time the stress differs is from a stop and even then it's not so much about AWD/RWD but the amount of rubber on the road. A 225 tire for instance in a RWD setup is 550mm of rubber resisting movement. In AWD that becomes a whopping 1100mm of rubber. If you dumped the clutch on a RWD car with 550mm tires, it would have the same exact amount of stress as 225mm AWD tire setup.

Your analogy of punching things doesn't work either. You're methods are so way off it's not even in the same sport. The above explains why from a stop about the AWD/RWD difference in stress. When in movement it's just very simple. A lighter car with 300tq will just move along faster then a heavier car with 300tq. Weight has no affect on the stress, it just allows the car to move faster. It isn't that hard to understand.

This is not true. A tire's coefficient of friction does not have a linear relationship with it's aspect ratio or width.

[Etos]

This is not true. A tire's coefficient of friction does not have a linear relationship with it's aspect ratio or width.

Fine- then replace the numbers so the correct coefficient is used. In the end, an AWD has more rubber to fight over a RWD from a launch. Weight plays a role from a stop as well but that's where it ends as well. Once the car is in motion, 300 tq from the engine to the trans is 300 tq regardless if the car is 1000 pounds or 4000. The only "lesser stress" a lightweight platform contributes is it takes less tq to gain a desired acceleration. If(and these are just made up numbers) it takes 100 tq to get a 4000 pound car to 60mph in 20 seconds, it'll take alot less tq to get a 1000 pound car to 60 in 20 seconds. With the high tolerance of these gearsets to take some abuse, non abusive levels like that are non-issue at all.

[BrandonDrums]

Tq is Tq. It doesn't care how much the object weighs. If it weighs little, it'll just move along faster in a shorter amount of time.

The only time the stress differs is from a stop and even then it's not so much about AWD/RWD but the amount of rubber on the road. A 225 tire for instance in a RWD setup is 550mm of rubber resisting movement. In AWD that becomes a whopping 1100mm of rubber. If you dumped the clutch on a RWD car with 550mm tires, it would have the same exact amount of stress as 225mm AWD tire setup.

Your analogy of punching things doesn't work either. You're methods are so way off it's not even in the same sport. The above explains why from a stop about the AWD/RWD difference in stress. When in movement it's just very simple. A lighter car with 300tq will just move along faster then a heavier car with 300tq. Weight has no affect on the stress, it just allows the car to move faster. It isn't that hard to understand.

tq is an instantaneous measure of a twisting force. If that torque, for example is coming from a person standing on the end of a lever, it can only be applied at the rate at which gravity causes objects to accelerate toward earth.

Similarly, fuel only burns so quick and a engine can only change the rate in which it increases it's rotational speed so quick. It's true, just pop your car in neutral and see that when you floor the gas pedal, the engine doesn't immediately hit the rev-limiter.

I mean, just go ride a bike. You can exert x amount of torque right? Put your bike in first gear and pedal as hard as you can with a piece of cardboard between your feet and the pedal. You'll probably hardily indent the cardboard and you'll reach your max speed pretty quick.

Now tie your bike to a tree, put the bike in top gear and pedal as hard as you can with the cardboard underneath your feet. The cardboard is way more chewed up right, your tired but you haven't gone anywhere.

Torque gives a really big **** about how much weight it's toting around.

[Xusia]

I think this boils down to rate of change of input force (engine torque) vs. resistance (traction and inertia). Without some kind of resistance, there isn't much stress being put on the transmission (or any part of the drive train, for that matter). If the rate of change of the input force (the rate at which the engine applies more and more torque as revs climb) exceeds the ability to dissipate that force (the force being resistance, and dissipated via acceleration), stress on the transmission increases - presumably until there is no additional torque to be added, or until something gives (tires break free, transmission breaks, etc.). All other things being equal, as weight is lowered, resistance is lowered as well. The tires are more apt to break free, and the whole car has less inertial resistance, making it easier to dissipate the input force.

Now, some people are saying the car will just accelerate faster, causing the stress on the transmission to remain the same. This is true so long as the overall resistance remains the same. The assumption being made here is that because the input force (engine torque) is the same, the equation will balance and the output will result in whatever [faster] acceleration will keep the resistance the same. As has been pointed out, there is a limit to how much more force the engine can apply. If the weight reduction is such that the input force is able to be dissipated more quickly than the engine can increase the input force, then stress is actually reduced.

So will the stress on the transmission be the same or less? I don't think anyone can answer that at this point because no one knows for sure what impact the reduced weight will have on this car (since it's not done yet and all...). Perhaps someone with the appropriate engine data and a lot of math skills could take a crack at it, but until then I propose we stop speculating and wait until we have actual data. :)

[Etos]

tq is an instantaneous measure of a twisting force. If that torque, for example is coming from a person standing on the end of a lever, it can only be applied at the rate at which gravity causes objects to accelerate toward earth.

Similarly, fuel only burns so quick and a engine can only change the rate in which it increases it's rotational speed so quick. It's true, just pop your car in neutral and see that when you floor the gas pedal, the engine doesn't immediately hit the rev-limiter.

I mean, just go ride a bike. You can exert x amount of torque right? Put your bike in first gear and pedal as hard as you can with a piece of cardboard between your feet and the pedal. You'll probably hardily indent the cardboard and you'll reach your max speed pretty quick.

Now tie your bike to a tree, put the bike in top gear and pedal as hard as you can with the cardboard underneath your feet. The cardboard is way more chewed up right, your tired but you haven't gone anywhere.

Torque gives a really big **** about how much weight it's toting around.

Again you are taking analogies that don't apply. Tying a bike down to an immovable object doesn't represent weight, it represents RESISTANCE. Same thing with picking a lower gear vs higher gear, it's again RESISTANCE, not weight. Xusia hit the nail on the head with that one. I didn't mean that torque doesn't give a **** about weight in all aspects, just the stress it applies at it's given rating.

Where I don't agree with Xusia is that no one knows. There's plenty who know for a fact they just aren't most likely on this board and are working in the automotive industry. I'll try asking Micah what's his stance on this considering he does alot of work in the diesel industry for tractors and has many many years of experience and knowledge.

I just sent micah a PM and once he gets back to me I'll CnP it here. I believe the question is phrased very unbiasedly:


I got a question for you that's been a great debate over at FFR forums for the 818.

People are arguing about the stress the transmission gets based on the weight of the vehicle.

One side of the argument is that since the 818 is 1800 pounds and much ligther then a WRX, that while in motion the stress of the transmission will be lessened.

The other side is that the stress will be close to the same because all the lighter weight does is lower resistance to movement(acceleration) and thus the stress on the trans is the same.

Additionally your thoughts from a stop with an 1800 pound car vs a 3200 pound car(take AWD/RWD out of the equation for now).

If you could also cite your expertise as your background knowledge to what leads you to believe your thoughts.

Thanks, it's always a blast to have a conversation with you

[Xusia]

I eagerly await his response. One thing though - and I think it's paramount here - is he familiar enough with the EJ series engines to adequately answer the question? The rate at which revs build (i.e. the rate at which additional torque is applied) is different from engine to engine, and in my experience, vastly different from gas to diesel.

[Evan78]

Brandon, I understand that there is rotational mass in the system that does not change (pistons, rods, crank, flywheel, transmission gears, etc), but I don't know if going from a 3100lb chassis to a 1800lb chassis is such a drastic change that all of those components are now the biggest part of the equation and that an 1800lb chassis represents a trivial amount of weight for the engine to push around. We're cutting chassis weight by about 40%, not 90%. As was stated earlier by someone else (Phyrram?), the amount of torque applied will be about the same, it will just be applied for less time (assuming both setups are accelerating to the same speed at full throttle).

[Etos]

I eagerly await his response. One thing though - and I think it's paramount here - is he familiar enough with the EJ series engines to adequately answer the question? The rate at which revs build (i.e. the rate at which additional torque is applied) is different from engine to engine, and in my experience, vastly different from gas to diesel.

He's one of the best when it comes to EJ motors. He knows a great deal about them. He and Dom are essentially the go to guys when it comes to EJ motors. Right now he's working with TiC race car to make a (I believe) 2.5 that revs to 10k RPM reliably. He's done alot of work in the pistons field helping JE design them for his applications. There's no question on his qualifications in the subaru world.

[Evan78]

Is this the same Micah that goes by Homemade WRX on nasioc and is in college or a recent graduate?

[RossLH]

Is this the same Micah that goes by Homemade WRX on nasioc and is in college or a recent graduate?

And founder of a very successful engine building business (3MI Racing) and arguably the best independent EJ builder in the country. The guy knows his stuff, and thats a grand understatement.

[Xusia]

He's one of the best when it comes to EJ motors. He knows a great deal about them. He and Dom are essentially the go to guys when it comes to EJ motors. Right now he's working with TiC race car to make a (I believe) 2.5 that revs to 10k RPM reliably. He's done alot of work in the pistons field helping JE design them for his applications. There's no question on his qualifications in the subaru world.

Perfect! I can't wait to hear what he has to say. (Seriously. I'm very curious) :)

[Etos]

Is this the same Micah that goes by Homemade WRX on nasioc and is in college or a recent graduate?

It is Homemade/3MI yes. I don't think he's a recent graduate. He's been in the field for a very long time.

[csdilligaf]

So regaurdless of the on going math disscussion. How about the actuall difference from a turbo and non turbo 5MT. Does one have better, bigger mainshaft and wider gears or is the only difference the gear ratio's? I am looking for a WRX 5MT and they are not nearly as plentyfull as just the Naturally Aspirated Impreza 5MT. I asked on NASIOC and only got "most likely"

[Etos]

So regaurdless of the on going math disscussion. How about the actuall difference from a turbo and non turbo 5MT. Does one have better, bigger mainshaft and wider gears or is the only difference the gear ratio's? I am looking for a WRX 5MT and they are not nearly as plentyfull as just the Naturally Aspirated Impreza 5MT. I asked on NASIOC and only got "most likely"

It's very easy to find a WRX 5MT. Go to http://forums.nasioc.com/forums/forumdisplay.php?f=151 and search transmission. The first page alone had 5 WRX transmissions. They vary in price from $300-$800+.

[Evan78]

So regaurdless of the on going math disscussion. How about the actuall difference from a turbo and non turbo 5MT. Does one have better, bigger mainshaft and wider gears or is the only difference the gear ratio's? I am looking for a WRX 5MT and they are not nearly as plentyfull as just the Naturally Aspirated Impreza 5MT. I asked on NASIOC and only got "most likely"I don't have an answer on the differences, but if you're hunting for a tranny alone, the biggest list I know of (http://www.northursalia.com/techdocs/trannychart/trannychart.html) is maintained at NorthUrsalia.com. The transmission part number/code should be useful for verifying that a given tranny is being described properly. Ratios are in the chart as well.

[csdilligaf]

Yes, I have been looking on NASIOC classifieds and useing the Rallispec sheet, so far they are Broken, old or both. On Ebay I can find 09-12 non turbo 5MT's with 8K miles for $450. If there is not a difference in the mainshafts or gear width's and it is simply the ratio, They would be the way to go.

[Evan78]

You should be able to get answers in the transmission forum. If a search doesn't turn up anything, just post a new thread.

AndrewTech (http://andrewtechautomotive.com/) is a transmission shop that does a lot of Subaru transmission work. You might try giving them a call.

[BrandonDrums]

Again you are taking analogies that don't apply. Tying a bike down to an immovable object doesn't represent weight, it represents RESISTANCE. Same thing with picking a lower gear vs higher gear, it's again RESISTANCE, not weight. Xusia hit the nail on the head with that one. I didn't mean that torque doesn't give a **** about weight in all aspects, just the stress it applies at it's given rating.


Well, with more weight comes more inertia which is resistance. Tying a bike to a tree is the same as tying the bike to a really really heavy trailer. The added weight cases additional resistance. Applying the brakes while applying throttle is adding resistance without weight.

To prove that mass has inertia, we can refer to the wiki entry on inertia (http://en.wikipedia.org/wiki/Inertia) here

"Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by applied forces. Inertia comes from the Latin word, iners, meaning idle, or lazy...."


Brandon, I understand that there is rotational mass in the system that does not change (pistons, rods, crank, flywheel, transmission gears, etc), but I don't know if going from a 3100lb chassis to a 1800lb chassis is such a drastic change that all of those components are now the biggest part of the equation and that an 1800lb chassis represents a trivial amount of weight for the engine to push around. We're cutting chassis weight by about 40%, not 90%. As was stated earlier by someone else (Phyrram?), the amount of torque applied will be about the same, it will just be applied for less time (assuming both setups are accelerating to the same speed at full throttle).

Yeah, it won't be that much of a difference, the only reason I brought up the rotational limits of the engine is to highlight that F=MA when considering a mechanically generated force has upper limits in the adjustability of both Force and Acceleration. F=MA remains true in a frictionless environment but there's more complicated systems to consider in this example.

Also, engine torque is only rated at peak. An engine doesn't produce 100% of it's torque all the time. Ask anyone who has experience dyno tuning, if the rollers have a variable loading servo, you can literally see an engine's output increase as load increases.

In short, think of it this way. There's a reason trucks and suv's rated for towing come with a transmission oil cooler and have a special section in the user manual about how to drive with a trailer hitched. Added weight and load to a drivetrain causes additional stress. Conversely, reducing weight reduces stress on the drivetrain/engine.

Kinda like how it's harder for you to carry around another person on your back vs. walking around normally. Just think of the 818 as walking around normally and the rest of it's life as a WRX, it would be like you carrying someone on your back all day every day. Do you think your joints will feel better, worse or the same when the jerk stops piggyback riding your butt around?

Heck, the whole reason the 818 is cool is because it's so darn light weight. It's easier to accelerate, easier to stop, the tires will last longer and the performance increases.

It's so logical that somehow people can't figure it out. Of course reducing mass will cause less stress on everything involved. It's so simple why can't people at least accept that lighter weight means less wear and tear in general?

[Evan78]

I don't think anyone is arguing that the lighter chassis is easier on the transmission in general. The instance some of us are saying is going to be similar is peak capacity. Whatever torque/hp number you feel that the trans can handle in the WRX, some of us are saying that the same number will apply in the 818. Yes, components will wear less when they have to push around less weight, but in the case of "how much power can the WRX trans take", the number will be similar regardless of what chassis it's in. This assumes no slipping anywhere in the system of course (clutch, tires).

Many have made the argument that lighter weight means less stress on the trans, often employing the f=ma equation. I don't know why so many people neglect A, as if mass is going down and somehow acceleration is being held constant. I guess they plan on building 818's that are no faster than the WRX that they are using for weight comparison.

Exidous was the most recent person to do this, so I responded with a simple question of "what's up with acceleration?", hoping for a response from him that shows what his thought process is.

[Etos]

Well, with more weight comes more inertia which is resistance. Tying a bike to a tree is the same as tying the bike to a really really heavy trailer. The added weight cases additional resistance. Applying the brakes while applying throttle is adding resistance without weight.

To prove that mass has inertia, we can refer to the wiki entry on inertia (http://en.wikipedia.org/wiki/Inertia) here

"Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by applied forces. Inertia comes from the Latin word, iners, meaning idle, or lazy...."



Yeah, it won't be that much of a difference, the only reason I brought up the rotational limits of the engine is to highlight that F=MA when considering a mechanically generated force has upper limits in the adjustability of both Force and Acceleration. F=MA remains true in a frictionless environment but there's more complicated systems to consider in this example.

Also, engine torque is only rated at peak. An engine doesn't produce 100% of it's torque all the time. Ask anyone who has experience dyno tuning, if the rollers have a variable loading servo, you can literally see an engine's output increase as load increases.

In short, think of it this way. There's a reason trucks and suv's rated for towing come with a transmission oil cooler and have a special section in the user manual about how to drive with a trailer hitched. Added weight and load to a drivetrain causes additional stress. Conversely, reducing weight reduces stress on the drivetrain/engine.

Kinda like how it's harder for you to carry around another person on your back vs. walking around normally. Just think of the 818 as walking around normally and the rest of it's life as a WRX, it would be like you carrying someone on your back all day every day. Do you think your joints will feel better, worse or the same when the jerk stops piggyback riding your butt around?

Heck, the whole reason the 818 is cool is because it's so darn light weight. It's easier to accelerate, easier to stop, the tires will last longer and the performance increases.

It's so logical that somehow people can't figure it out. Of course reducing mass will cause less stress on everything involved. It's so simple why can't people at least accept that lighter weight means less wear and tear in general?

Ugh, ok let's try this again. By your own citation that "Inertia is the resistance of any physical object to a change in its state of motion or rest" a lighter car would be more stressful on the trans in a vacuum. Why? The lighter car has less force behind it. Going back to your F=MA, Force = Mass x Acceleration. So if the 818 is 1800 pounds going at 60mph, and a WRX at 3200 pounds at 60mph, which is going to have more force? The WRX. So if it has MORE FORCE, it takes LESS power to keep it moving in it's direction. Ofcourse that's all BS cause it doesn't take gravity into account. But see how easy it is to spin and twist logic? That is all you're doing for your F=MA cause you CONSTANTLY take A out of your equation just like I took gravity out of my BS example.

Ofcourse an engine doesn't produce 100% of it's torque all the time, that's why we aren't hitting top speed every time we put a car into drive. You don't need a dyno to show this, jump in a car, go WOT, go half throttle. There ya go, difference in torque output.

Trucks that tow have a trans cooler cause you're going OVER or VERY CLOSE what an automatic trans can handle in weight. Auto transes use a combination of planetary gears and clutchpacks. Those clutchpacks when at their limit start producing ALOT of heat. Heat is the biggest enemy of an auto trans. This is an invalid argument toward weight again. Look at even RACE CARS that reduce a TON of weight. They too, light as they maybe, use trans coolers. FACTORY STI'S COME WITH TRANS COOLERS!

Again with the analogies that don't work with the piggy back. Like you said before a car doesn't put out 100% constant torque, it's controlled by the throttle. Let's use that piggy back in an analogy that does work. Take a back pack that weighs 10 pounds. See what you're top speed is as well as how long it takes you to run a 4 miles at your fastest, never slowing down. Do the same with now 50 pounds. Again top speed you can go, give it EVERYTHING you go, go WOT! Guess
what, you're gonna be just as tired, only difference is you won't move as fast. Again, you never take acceleration into account, you just constantly throw it out the window.

Lighter weight does give less wear in tear in alot of places. Engine/trans is NOT one of them on say a track. They are being pushed just the same. They don't care what the weight is minus being tied down by a tree(read, extreme resistance). On the street, yes you'll have less wear and tear but it's so negligible how little difference there will be. Once you go WOT, 300tq is 300tq. Engine don't care, trans don't care.

I'm still waiting to hear back from Micah.

[apexanimal]

think of it in reverse too...

which will require bigger/beefier brakes to bring it to a stop in the same distance: a 4000lb lux, or a 2800 compact?

[BrandonDrums]

Ugh, ok let's try this again. By your own citation that "Inertia is the resistance of any physical object to a change in its state of motion or rest" a lighter car would be more stressful on the trans in a vacuum. Why? The lighter car has less force behind it. Going back to your F=MA, Force = Mass x Acceleration. So if the 818 is 1800 pounds going at 60mph, and a WRX at 3200 pounds at 60mph, which is going to have more force? The WRX. So if it has MORE FORCE, it takes LESS power to keep it moving in it's direction. Ofcourse that's all BS cause it doesn't take gravity into account. But see how easy it is to spin and twist logic? That is all you're doing for your F=MA cause you CONSTANTLY take A out of your equation just like I took gravity out of my BS example.

Ofcourse an engine doesn't produce 100% of it's torque all the time, that's why we aren't hitting top speed every time we put a car into drive. You don't need a dyno to show this, jump in a car, go WOT, go half throttle. There ya go, difference in torque output.

Trucks that tow have a trans cooler cause you're going OVER or VERY CLOSE what an automatic trans can handle in weight. Auto transes use a combination of planetary gears and clutchpacks. Those clutchpacks when at their limit start producing ALOT of heat. Heat is the biggest enemy of an auto trans. This is an invalid argument toward weight again. Look at even RACE CARS that reduce a TON of weight. They too, light as they maybe, use trans coolers. FACTORY STI'S COME WITH TRANS COOLERS!

Again with the analogies that don't work with the piggy back. Like you said before a car doesn't put out 100% constant torque, it's controlled by the throttle. Let's use that piggy back in an analogy that does work. Take a back pack that weighs 10 pounds. See what you're top speed is as well as how long it takes you to run a 4 miles at your fastest, never slowing down. Do the same with now 50 pounds. Again top speed you can go, give it EVERYTHING you go, go WOT! Guess
what, you're gonna be just as tired, only difference is you won't move as fast. Again, you never take acceleration into account, you just constantly throw it out the window.

Lighter weight does give less wear in tear in alot of places. Engine/trans is NOT one of them on say a track. They are being pushed just the same. They don't care what the weight is minus being tied down by a tree(read, extreme resistance). On the street, yes you'll have less wear and tear but it's so negligible how little difference there will be. Once you go WOT, 300tq is 300tq. Engine don't care, trans don't care.

I'm still waiting to hear back from Micah.

I didn't make the laws of physics. Newton is the one that defined the basic laws of motion including defining the relationship of mass and inertia.

You're pretty dense yourself to be arguing with universally accepted scientific truths.

Also, I don't throw acceleration out the window, I've done more to highlight the limits of a mechanical system's acceleration than you have. Seems to me you went to the Sarah Palin School of Going Rogue Against Common Sense University.

[PhyrraM]

"Scientific truths" don't apply directly. There is a transmission and multiple gears involved. Gears multply and divide torque. There are many other forces and variables to deal with than simply Mass and Acceleration. You can't take a simple formula layed out 100s of years ago and directly apply it to this "conversation". The basics are great for teaching, understanding and learning, but in the real world rarely apply without further scrutiny. Space is a vacuum, thet's where you can study basics.

The answer will be forthcoming sometime after the first cars are built and trounced on. Not before, regardless of how many words we put in this thread.

[Evan78]

think of it in reverse too...

which will require bigger/beefier brakes to bring it to a stop in the same distance: a 4000lb lux, or a 2800 compact?Your logic is correct, but not relevant to the discussion. Brandon is starting to forget the origin of the discussion. See my post #144 above yours.

[StatGSR]

F=MA is all fine and dandy when your are talking about an object in linear motion.... but all this transmission/engine/wheel stuff isn't in linear motion. its all in rotational motion... tau = I*alpha , tau = Torque, I = mass moment of inertia, and alpha = angular acceleration.... second law still applies, you guys are just using the wrong units...

[apexanimal]

Your logic is correct, but not relevant to the discussion. Brandon is starting to forget the origin of the discussion. See my post #144 above yours.

noted...

[Smitty911]

So I guess just driving it until it won't move won't tell us anything? ;)

Of course I bring nothing to the discussion table.

Smitty

[Exidous]

Ugh, ok let's try this again. By your own citation that "Inertia is the resistance of any physical object to a change in its state of motion or rest" a lighter car would be more stressful on the trans in a vacuum. Why? The lighter car has less force behind it. Going back to your F=MA, Force = Mass x Acceleration. So if the 818 is 1800 pounds going at 60mph, and a WRX at 3200 pounds at 60mph, which is going to have more force? The WRX. So if it has MORE FORCE, it takes LESS power to keep it moving in it's direction. Ofcourse that's all BS cause it doesn't take gravity into account. But see how easy it is to spin and twist logic? That is all you're doing for your F=MA cause you CONSTANTLY take A out of your equation just like I took gravity out of my BS example.


Not sure if this was meant to be a serious example. I see the whole BS thing but using an 1800lb vehicle at 60mph is a bad example due to the acceleration being zero. The force required is a product of drag, friction and heat at a constant velocity. The WRX requires more force due to increased drag coefficient and increased friction(maybe, we'll see what it looks like once the 818 is released).


I don't think anyone is arguing that the lighter chassis is easier on the transmission in general. The instance some of us are saying is going to be similar is peak capacity. Whatever torque/hp number you feel that the trans can handle in the WRX, some of us are saying that the same number will apply in the 818. Yes, components will wear less when they have to push around less weight, but in the case of "how much power can the WRX trans take", the number will be similar regardless of what chassis it's in. This assumes no slipping anywhere in the system of course (clutch, tires).

Many have made the argument that lighter weight means less stress on the trans, often employing the f=ma equation. I don't know why so many people neglect A, as if mass is going down and somehow acceleration is being held constant. I guess they plan on building 818's that are no faster than the WRX that they are using for weight comparison.

Exidous was the most recent person to do this, so I responded with a simple question of "what's up with acceleration?", hoping for a response from him that shows what his thought process is.

I do see what you are saying here. Given half the mass, the acceleration should double given the same force with all other influences being equal. It seems that at the very moment that the rotational force begins applying pressure to the wheels would be the same in the heavy vehicle as it is the light one. Once motion is achieved with the reduced mass of the 818, the acceleration is increased given the force created by the motor is equal. I was thinking the torque of the motor would vary based on the weight of the vehicle. Obviously flawed.

[BrandonDrums]

So I guess I stand corrected. I should stop weight lifting, apparently I'll get the same amount of exercise if I just flap my arms around without any dumbbells because they'll accelerate so much faster my arms will be equally sore.

Thanks guys!

[Evan78]

If lifting 500 lbs at a rate of 1g breaks your arm, lifting 250 lbs at 2g will also break your arm.

Nobody said it isn't more work to carry around 3000 lbs than 1800 lbs. We were talking about the upper limit of how much peak power a transmission can handle.

[Exidous]

Weight lifting is different and refers to work being done by applying a force times the distance traveled. We are looking at the force required to snap the humerus by accelerating the weights too fast. :-)

[BrandonDrums]

Weight lifting is different and refers to work being done by applying a force times the distance traveled. We are looking at the force required to snap the humerus by accelerating the weights too fast. :-)

wow, this is getting ridiculous. Phyrram said it, with all the rotational forces going on F=MA isn't a linear equation. He happens to think of it differently than I do but my point is, the peak "A" of F=MA in a dynamic, mechanical system has upper limits.

Now, a rocket makes thrust, it's speed cannot change the amount of force being exerted and the object will accelerate in accordance with the mass of the object because the force is always equal.

On a car, the engine has to make enough power to spin the wheels at the same rate as the car is moving over the pavement IN ADDITION to applying a net force above and beyond to accelerate the whole vehicle. Regardless of weight, there's a consistent loss in net force as the car gains speed across the ground. Adding weight makes it harder to maintain speed AND harder to accelerate. Removing weight takes a lot of friction out of the equation but the acceleration is still limited to how fast the engine can turn to get the wheels to spin fast enough to maintain it's speed so Acceleration isn't proportionate to the decrease in mass. Even in a vacuum absent of all friction, gears are required to get a car to hit a high speed and acceleration decreases as you shift up through the gears because the mechanical disadvantage increases in higher gears. Torque is reduced at the wheels in higher gears.

Another example might be a lever. Gears are simply mechanical levers that allow varying degrees of mechanical advantage/disadvantage in a rotating system. Say you're on a see-saw with your twin who, like you weights exactly 150 lbs and the see-saw's fulcrum is exactly in the middle. You and your twin will be balanced at that point. Now say, your 8 year old, 75-lb cousin swaps place with your identical 150-lb twin. You fall to the ground while your cousin is are lifted up but only at 50% of the speed of gravity would pull you down (the fastest you can fall is only the rate at which gravity works on earth which is 9.8 m/s^2. Similarly, an engine has a max rate that it can increase it's rotational speed but that's besides the point for this example). However, if you move the fulcrum towards yourself by 50% (halfway between you and the original fulcrum), the system becomes balanced again right? 2 different weights on the see-saw adding up to less overall mass but you're both balanced on the board like before.

Don't say Acceleration is absent from that example as it's there, acceleration is equal to 0. We could make the same case using a Trebuchet or a catapult instead of a see saw and have nonzero acceleration numbers.

Similarly, in order for the gears to experience the same load as they did before the weight is reduced, the ratios will have to be increased to place more mechanical DISadvantage on the engine than it does in stock form. Reducing the weight of the vehicle from 3300 lbs to 1800 lbs is about a 45% decrease in mass. I would argue that the gear ratios would have to increase by a similar percentage to have the same amount of load as before the reduction in weight took place.

Make sense?

Bringing this back on topic, I believe the 5mt will be able to handle probably about 20% more power than before as Acceleration will increase but only by about half of what some of the others would suggest. There is merit to the argument that putting all the torque through 2 wheels vs. all 4 could make the ring and pinion gears get closer to their breaking point so on that argument only I could see the transmission handling even less than 20% of an increase of torque but still a strong jump. I believe the ring and pinion were designed to handle 100% of the torque for reasons we won't get into.

However, if the acceleration will increase proportionately to mass decrease were true which this entire post is meant to prove incorrect, we'd be looking at a about a 2.75 sec 0-60 (roughly a 45% improvement in proportion to the 45% decrease in weight) with a stock 2.0L wrx engine which we all know won't quite be the case.

I hope no one thinks I'm disregarding acceleration anymore after this one.

I'm totally kicking a super rotten long-dead horse here but this thread is a good example that we ALL know the acceleration won't increase proportionately to the 818's loss of weight vs. the wrx.

http://thefactoryfiveforum.com/showthread.php?5036-Perfomance-Expectations

I see no posts assuming the 818 will go 0-60 in less than 3 seconds with a stock motor. That alone proves that we instinctively know acceleration isn't going to be so fast that the transmission will break as often as before.

/endlongassrant

[juha_teuvonnen]

Do we have any ideas of other gear boxes that might suite this build well? I'm really hoping to reach supercar level performance as I've got a already nicely built subaru. (400awhp turned up). I've broken quite a few 5 speeds including STi-RA gears. I will say my RA-box help up through YEARS of drag racing and rally racing and me beating the tar out of the box.

I'm also currently setup as a RWD subaru and i'm pretty sure I broke a stock wrx rear and I know i've already chewed up a front diff on 16psi.

Should we have a separate thread on vehicle dynamics and implications for transmission strength?

To the best of my knowledge the consensus among Subaru folks is that the WRX trans is not particularly strong, and a cost-effective way to make it strong is not known at this time. It is generally recommended to go with STI trans for STI swaps, because it's a completely different trans altogether. STI trans are rare, big, heavy and cost a lot of money. To my knowledge both WRX and STI are all wheel drive cars, so the Subaru trans will need to be modified, which is not free.

Why not use a Porsche 944/Audi 5000 "type 016" transaxle? Rumor has it that they are good for something to the tune of 400 Hp. I know for a fact that they are relatively inexpensive (300-500 used, 1500 rebuilt) and readily available, because many a Porsche 944 got parted after the timing belt broke (known weakness of interference design M44 engine). An adapter would need to be made for the WRX engine, but modifying an AWD trans to a FWD configuration is not free either, so it's a wash.

Using a Porsche trans enables all kinds of interesting options. I would actually prefer GM Ecotec engine to the subaru. The Ecotec LNF is good for 290 Hp in practically stock configuration (mild tune and a couple of bolt-ons from GM). Used LNF can be had for a 2-3 grand, a brand new crate engine can be had for 3500 (without ancillaries). Even with the best rubber available today, an 1800 lb car with 300 Hp will likely have traction problems. For a budget build one could use an LK9 engine out of a turbo Saab (220 Hp) which can be had used for a grand. Even more budget-conscious could use a 2.2 or a 2.4 N/A Ecotec, these are dirt cheap used (500 bucks). With a little under 200 Hp an 1800 lb car will still have the power-to weight ratio to beat the crap out of most 4 wheeled things on the road.

[shim2]

Reason they went with subi is because of the boxer engines low COG. Yes subi's are awd, the 5spd can be converted to 2wd fairly easily whereas the 6spd I believe can't be converted to 2wd. Mating another transmission to an engine it wasn't originally designed for increases the cost. I'm sure it would have pushed the cost goal of the 818 well beyond 15k.

There is a company (out of Australia I believe) that makes stronger gears for the 5spd but it isn't cheap, I think it's to the tune of 2-4k. Also the Ej205 from what I've read can handle up to 300whp on stock internals beyond that you have to go with forged pistons ect... 300whp in a 1800 pound car IMO is more than enough to get you into trouble.

Also, A donor wrx can be had for cheap, I've seen them sell for 2k on copart.com (not including fees and shipping) FF's goal is to have a one donor car swap not have bits and pieces from 8 different cars.

With all of their goals in mind it makes complete sense why they went with 02-07 impreza or wrx

[Xusia]

From my recollection in a previous thread, the 6 speed can be converted to 2wd fairly easily as well (don't take my word, though -I'm no expert). The main issue is fit. the 6 speed is bigger, and - most importantly - much longer (about 8") than the 5 speed.

The inherent limitations of stock transmission (I don't know that I would term is at weak) is one reason why my ultimate target hp is around 300. That's easily obtainable from the engine without much hassle or having to go with forged internals (or if we can figure out how to use an H6, it would be close enough stock), and the transmission should be fine as long as I don't do anything stupid. It's the path of least resistance...

[PhyrraM]

......Why not use a Porsche 944/Audi 5000 "type 016" transaxle?........... I would actually prefer GM Ecotec engine to the subaru. .............. For a budget build one could use an LK9 engine out of a turbo Saab (220 Hp) ...............

Because, then your not building a FFR 818 anymore. Your building something else.

[juha_teuvonnen]

Reason they went with subi is because of the boxer engines low COG. Yes subi's are awd, the 5spd can be converted to 2wd fairly easily whereas the 6spd I believe can't be converted to 2wd. Mating another transmission to an engine it wasn't originally designed for increases the cost. I'm sure it would have pushed the cost goal of the 818 well beyond 15k.

There is a company (out of Australia I believe) that makes stronger gears for the 5spd but it isn't cheap, I think it's to the tune of 2-4k. Also the Ej205 from what I've read can handle up to 300whp on stock internals beyond that you have to go with forged pistons ect... 300whp in a 1800 pound car IMO is more than enough to get you into trouble.

Also, A donor wrx can be had for cheap, I've seen them sell for 2k on copart.com (not including fees and shipping) FF's goal is to have a one donor car swap not have bits and pieces from 8 different cars.

With all of their goals in mind it makes complete sense why they went with 02-07 impreza or wrx

I completely agree with you that Ecotec + Porsche/Audi trans would likely be more expensive and more PITA to build. The folks shooting for a budget build should, and very likely will likely stick with Subaru running gear. Ones looking for a more expensive/ higher performance build may run into the limitations of the subaru transmission. While there are many performance options for the internals WRX engine, all of them will likely blow the 15 grand target, probably by a good margin. It is generally cheaper to sell the WRX engine and buy a used JDM STI engine than to build up WRX. In both cases the strength of the transmission is going to be the limiting factor.

I would estimate the cost of the bellhousing adapter to be in the neighbordhood of $350, assuming a decent-sized group buy. Kennedy engineering sells adapter kits for 440, but that includes pilot bearing, flywheel and fasteners. While modifying a WRX trans to 2WD configuration is easy, what how much will it cost? I'm figuring easily over 200-250 for anything that requires the trans to be opened up, assuming a competent transmission shop is doing the job. I've rebuilt an Audi-style FWD transaxle once, and then taken it to a good shop to have the diff adjusted properly. To paraphrase Dirty Harry, "a man has got to know his limitations". So, IMHO a Porsche/Audi "typ 16" may be a viable option for the higher-powered Subaru engines. You will need custom axles, but I would expect them to be needed one way or another in a RWD configuration, even with a stock WRX engine. Even with a lighter car, you are putting all that power through 2 axles instead of 4. Say it's 1.5 times the torque (not 2x) because of the lighter car. You are still way beyond what the stock WRX axles were designed to do. Nothing will ruin your car, quite like the inner CV joint failure.The aftermath is never pretty, sometimes the car could be a total loss.

Ecotec is a great engine, but it's probably not worth the trouble, unless supported by Factory 5 kit as an option. Assuming the trade value of the WRX motor 1 grand less than that of Ecotec LNF, if you sell your Subaru motor and buy LNF, you are out about 1500 tops. The wiring and ECU is going to be a gigantic PITA, but there are outfits that will rig a standalone wiring harness out of a stock one and program the ECU for standalone operation. It costs somewhere around $500 and is way worth it. Then you get to cooling system and exhaust (time to get the trusty old TIG welder going, custom built stuff is expensive). Either you have expensive tools, have lots of time on your hands and are capable of doing a lot of fab work, or it's tons of money.

[thestigwins]

I thought one of the main reasons for the Subaru engine and drivetrain was due to the fact that this is a world car. They wanted a drivetrain that could be sourced around the world. I see no problem with looking into different engine/transmission combinations.

[Xusia]

Because, then your not building a FFR 818 anymore. Your building something else.

I don't think the engine defines the car. It may have different characteristics, perhaps even a different character, but so does every car that is custom built...

[PhyrraM]

IMHO, the main reason to choose a Subaru is that is it already, from the factory, basically set up for a longitudinal mid-engined setup using a VERY short motor. Some Audis are also this way, but the Audis have much longer motors and need more space between the seats and rear wheels.

If we are already having trouble with the idea of the H6 - which is only 3 cylinders long - making an inline 4 (4 cylinders long) fit is not looking good. If you lengthen the chassis, you've got to lengthen the body. Not really an 818 anymore at that point. I'm not against putting any type of motor or transmission you wish into it, just the amount of work makes it more of a homebuilt than something FFR intended. For example...How many of us still consider that Hennesy(?) thing a Lotus? IIRC, they don't even label it as a Lotus

[Evan78]

I agree with Xusia, the chassis defines the car a lot more than the engine does. Whoever sells a car gets to name it, so Hennessey call's their car a Hennessey Venom.

There are engine swaps all over the place, only the extreme purists say "it's not a (fill in the blank) anymore". GM LS v8 engines are put into nearly everything these days, do you see an LS powered RX7 and make up a new name for it? Even if you give it a new name, it's still a car that does all the things that cars normally do, so I don't see any reason to say it doesn't deserve discussion.

[juha_teuvonnen]

IMHO, the main reason to choose a Subaru is that is it already, from the factory, basically set up for a longitudinal mid-engined setup using a VERY short motor. Some Audis are also this way, but the Audis have much longer motors and need more space between the seats and rear wheels.

If we are already having trouble with the idea of the H6 - which is only 3 cylinders long - making an inline 4 (4 cylinders long) fit is not looking good. If you lengthen the chassis, you've got to lengthen the body. Not really an 818 anymore at that point. I'm not against putting any type of motor or transmission you wish into it, just the amount of work makes it more of a homebuilt than something FFR intended. For example...How many of us still consider that Hennesy(?) thing a Lotus? IIRC, they don't even label it as a Lotus

I see your point, and it's a good one. I am new to this board, and you clearly know more about the chassis in question than I do. If and H3 won't fit, the ecotec is unlikely to fit. Hence, it would need to be mounted transversely, which would require a completely different transmission altogether. That being said, it may be possible to use Cobalt SS transmission. I would also look into SRT-4 and MR2. It may be possble to have more drivetrain options for 818, any FWD will work so long as the transmission linkage uses cables.

IMHO the target audience for any kit car are mechanically inclined tinkerers, so more engine/driveline options would be a good thing.

[shim2]

I see your point, and it's a good one. I am new to this board, and you clearly know more about the chassis in question than I do. If and H3 won't fit, the ecotec is unlikely to fit. Hence, it would need to be mounted transversely, which would require a completely different transmission altogether. That being said, it may be possible to use Cobalt SS transmission. I would also look into SRT-4 and MR2. It may be possble to have more drivetrain options for 818, any FWD will work so long as the transmission linkage uses cables.

IMHO the target audience for any kit car are mechanically inclined tinkerers, so more engine/driveline options would be a good thing.

MR2's are transverse. That I'm sure of would never bolt to a subi boxer engine. Even if you could, you'd have to turn the boxer engine transverse would create all kinds of complications, again way more work that it would ever be worth. Ideally if you could somehow magically make it work with relative ease the 3sgte is probably one of the best engines to build high hp without needing sleeves.

TBH it would probably be easier to drop an a4/passat 1.8t in it since they're longitudinally mounted same as the subi boxer.

[juha_teuvonnen]

MR2's are transverse. That I'm sure of would never bolt to a subi boxer engine. Even if you could, you'd have to turn the boxer engine transverse would create all kinds of complications, again way more work that it would ever be worth. Ideally if you could somehow magically make it work with relative ease the 3sgte is probably one of the best engines to build high hp without needing sleeves.

TBH it would probably be easier to drop an a4/passat 1.8t in it since they're longitudinally mounted same as the subi boxer.

MR2 trans (or GM F35) would go together with transversely mounted Ecotec. A transversely mounted Ecotec should fit where longtitudaly mounted subaru boxer did, provided the engine bay is tall enough.

A longtitudaly mounted engine (looks like subaru flat 4 is the only viable choice given the chassis constraints) could be mounted to a lingtitudal trans from Porsche 944/audi 5000 or a modified Subaru trans, converted to 2WD configuration.