To Turbo or not to Turbo that is the Question - or - how much is too much?

[jlahl3160]

Being new to this, and asking a few questions, I found myself asking which donor to choose. I think I would like a go-fast car that would knock my socks off but in reality.... a sort-a-fast car is good enough for my abilities. I started to think of how the 818 would compare with different engines in it to other common rides. So I made a chart of data found a Wiki.. Which may not be the most accurate, but close enough for this purpose.

I found this chart to be helpful in my thinking of what version donor I would go after.
After I looked at this, I think I may go more conservative on the build .. and not a monster. If I can't control the thing, what good is it (and you would see my brand new build on Copart with all the others, wrecked).

John

Revised table




Car
Engine Size (L)
hp
Weight (lbs.)
Wheel Base
lbs./hp


Triumph Spitfire ('73) Car
1.5 Engine size
53 hp
1750 Weight
83 Wheel Base (in)
33 lbs./hp


MGB ('65) Car
1.8 Engine size
94 hp
1850 Weight
91 Wheel Base (in)
20 lbs./hp


BMW Z3 Car
1.9 Engine size
138 hp
2590 Weight
96.3 Wheel Base (in)
19 lbs./hp


Miata (2nd Gen) Car
1.8 Engine size
140 hp
2350 Weight
89.2 Wheel Base (in)
17 lbs./hp


BMW Z4 Car
2.0 Engine size
150 hp
2590 Weight
98.3 Wheel Base (in)
17 lbs./hp


Sunbeam Tiger Car
4.3 Engine size
164 hp
2564 Weight
86 Wheel Base (in)
15.6 lbs./hp


BMW Z4 Car
3.0 Engine size
231 hp
3241 Weight
98.3 Wheel Base (in)
14 lbs./hp


Corvette LS1 C5 Car
5.7 Engine size
345 hp
3246 Weight
104.5 Wheel Base (in)
9.4 lbs./hp


Corvette Grand Sport Car
6.2 Engine size
400 hp
3214 Weight
105.7 Wheel Base (in)
8.0 lbs./hp


Corvette Z06 (C6) Car
7.0 Engine size
505 hp
3180 Weight
105.7 Wheel Base (in)
6.3 lbs./hp


Corvette ZR1 (C6) Car
6.2 Engine size
638 hp
3405 Weight
105.7 Wheel Base (in)
5.3 lbs./hp


818 Car
2.0 Engine size
140 hp
1800 Weight
94 Wheel Base (in)
12.9 lbs./hp


818 Car
2.5 Engine size
165 hp
1800 Weight
94 Wheel Base (in)
10.9 lbs./hp


818 Car
2.0 w/ T Engine size
217 hp
1800 Weight
94 Wheel Base (in)
8.3 lbs./hp


818 Car
2.5 w/ T Engine size
220 hp
1800 Weight
94 Wheel Base (in)
8.2 lbs./hp


818 Car
2.5 w/ T Engine size
340 hp
1800 Weight
94 Wheel Base (in)
5.3 lbs./hp


818 Car
2.0 w/ T Engine size
400 hp
1800 Weight
94 Wheel Base (in)
4.5 lbs./hp



Revision #2: 11/9/2012

[wallace18]

You most likely could buy a NA donor for a lot less $.

[bromikl]

You could start with a 2.5 NA motor and swap it out if ever feel the need. I'm in the 'predictability trumps power' crowd. I doubt you'll be disappointed with a power-to-weight ratio that's better than a Z4.

[Accro]

My 2 cents, I just finished a season of mechanic/driving training at a place called Bridgestone Racing Academy (www.race2000.com if you care) And we drove cars that were 1000lbs and about 170bhp so 5.8 lbs/hp. If you never plan on tracking your car, you don't need to even come close to that. My DD is an MR2, which is about 12 lbs/hp and it's still fun to drive. My rough guess is, if you want a really fun DD, go for the 8-10 lbs/hp range. If you want a track car, well, the lower the better. It's a lot less scary spinning at a track then on the street. And the street is no place to test a car's limits. Like Wallace said, you could start NA, or stock turbo if you want, and upgrade from there. My plan is to get around 300whp, and that way i get to relive driving those crazy formula cars. Hopefully the handling isn't too far off either (we only ran 195 width RE-11s)

[Kalstar]

Lotus Elise is 10 p/w. A 2.5 na 818 would be around the same p/w. I think na wil be more than enough for the street. Wrx will be overkill in most situations.

[NonProfit]

Hey John, I agree with you. I wonder how many folks are going to build a car with so much power it's more scary than fun.

[timmy318]

Hey John, I agree with you. I wonder how many folks are going to build a car with so much power it's more scary than fun.

There's probably going to be some people who decide to do that but then realize that so much hp in such a little car is simply too much.... I plan on getting around 200-230wph with a 2.5 WRX motor

[Erik W. Treves]

turbo..no question

[Mechie3]

Stock turbo 2.5 WRX here. Both my WRX and FM were around 10 lbs/hp. The FM has given me a lot of lightweight RWD experience. I still see people talking about wanting 400whp and think "holy crap....they're going to die". From Wiki, the 97 McClaren F1 car was 4.3lb/hp, a Murcielago is 5.1, Ariel atom 500 V8 is 2.45, and the 2005 BMW F1 car was 1.43. 400 whp is ~ 470chp (assumes 15% loss) and equates to 3.8lb/hp. Doing 470hp in a turbo 4 means nothing, nothing, nothing. BOOOOOOOOOST! That would be hard to control.

As others said, you can always start out NA (as most of the donor parts will be similar) and upgrade later (though you'd have to upgrade the trans and the motor, ecu, wiring, etc). it's certainly a cheaper way to start out, though upgrading later might cost you more if you piece part it vs buying a full donor (but then you're left selling off what you don't need).

[PhyrraM]

Very, very few people have ever driven a car with a power-to-weight ratio better than 10:1 WITHOUT traction control and 3500+ pounds to keep it planted. So they simpley have no basis on what that an 818 might feel like.

MANY, MANY 818 builders are in for a very rude awakening (suprise?).

Stock 227 horsepower WRX motor is more than enough for a street driven 818.

At this early stage in the 818's life, I guess it's really no difference than trying to choose what to order at the steakhouse - on an empty stomach.

[timmy318]

Very, very few people have ever driven a car with a power-to-weight ratio better than 10:1 WITHOUT traction control and 3500+ pounds to keep it planted. So they simpley have no basis on what that an 818 might feel like.

MANY, MANY 818 builders are in for a very rude awakening (suprise?).

Stock 227 horsepower WRX motor is more than enough for a street driven 818.

At this early stage in the 818's life, I guess it's really no difference than trying to choose what to order at the steakhouse - on an empty stomach.

I hear yea!

[NISMO_RB25]

I have been addicted to boost since my first turbo RX-7, so for me the decision to go turbo was an easy one. I have owned several vehicles with 7 to 8lbs per hp and completely agree that some of these people are going to die if they are shooting for 400 or more HP. My GTR is 7lbs/hp and driving it is something most people could do thanks to the AWD/ABS and brembo brakes to save your butt. Take my old Mazdaspeed MX-5 that was 8.3lbs/hp on the other hand and at any moment that thing could kill you. Just accelerating in third would cause the rear to break free as the boost came on and that was after swapping the gears to 3.63s from 4.10s. At 300hp to the wheels in a 2500lb car I can assure you 227 at the crank in 1800lbs will be more than enough for most drivers and probably way too much for most. Just doing an online calculator says that the 818 with stock turbo power should run low 12 second quarter miles times. 300hp would put you deep in the 11s. 400 would be 10s if you managed to ever get enough traction to make it down the strip. Lots of people have owned "quick" cars, but for most this will be the first truly fast car. I am just hoping all the people that wrap one of these around a tree don't ruin insurance cost for the rest of us. If you have never really driven a truly fast car, I would highly recommend you stick with NA and upgrade later. You will still destroy just about everyone on a road course while you work up your skills to handle the additional power of the turbo engines. Be safe out there!

[jlahl3160]

Thank you all for your comments.

I believe in going conservative at the start.... though I would hate to have regrets, as IMO the cost difference is so low with a salvage donor.
If I were to do a NA, I believe it could be a DD with lots of fun, low risk. Once being successful at the first build, a second build would result in a more professional looking car with plenty of go... with all the improvements and learning, it would be a dream.

What would it look like going to the track in a 818S towing a 818R? Soo....oo sorry.... I need to go clean myself up.

But seriously... a most people have never gotten close to driving a Z06, much less than have one for a DD.. Could you picture it out in the rain with no traction control? I would need to go back to driving school.

John

[Mechie3]

One thing I'm going to love about this is it's almost a street legal version of my FM. Sure, it's not an open wheel car, but it's RWD, mid engine, manual steering, manual brakes, and raw power.

As you mentioned, you could always build 1, sell it, and build a second.

[wleehendrick]

Very, very few people have ever driven a car with a power-to-weight ratio better than 10:1 WITHOUT traction control and 3500+ pounds to keep it planted. So they simpley have no basis on what that an 818 might feel like.

I agree that many Subbie drivers that build a 818 may be (unpleasantly) surprised with the dynamics and will have to learn to respect the right foot, as you can't get away with ham-fisted driving like you can in a much heavier, front weight biased AWD vehicle. However, I think there are more than "very, very few people" on this forum that have experience with powerful RWD cars. My daily driver is a 350Z (with less than 3500lbs and around 10lbs/hp) and I turn off the traction control all the time (a friend calls me Tokyo Drift when he wants to annoy me)... A coworker has a C6 Z06 (505hp, BTW) and some of the autocrossers on here probably have monsters. I do realize that the 818 will be even more of a handful, with better power/weight, and a low polar moment of inertia that makes it easy to rotate (spin); even a NA build will certainly require you to be on our toes at all times.

[wallace18]

A good racing or performance driving school is worth its weight in gold. Car control is mostly overlooked by many street drivers. There is a reason for 3 pedals in the car. It is how you use them that makes the differance.

[Benji]

Very, very few people have ever driven a car with a power-to-weight ratio better than 10:1 WITHOUT traction control and 3500+ pounds to keep it planted. So they simpley have no basis on what that an 818 might feel like.

MANY, MANY 818 builders are in for a very rude awakening (suprise?).

Stock 227 horsepower WRX motor is more than enough for a street driven 818.

At this early stage in the 818's life, I guess it's really no difference than trying to choose what to order at the steakhouse - on an empty stomach.

THIS WITH FREAKING BELLS ON.

If you've ever driven an old Miata (with no traction control) or a Lotus Elise, you'll realise what even 160bhp will do for you in a car this light, *REALLY*. I cannot put enough emphasis on PhyrraM post.

Personally I'd be happy with a stock NA motor as it's probably the same power as my Miata in something that weighs over a 100Kg lighter than my Miata and that can already be a handful. If I were to truly go 'all out' and use the S for some track duty as well (which I would), then I'd personally go with an EZ30/36 for:

1. Around 100bhp more than my Miata!
2. That sound!

And I'd hopefully get the car down below 790kg and believe me, at that point with no traction control you'll need to be on the ball most of the time and be very concious of what you are doing with the throttle at all times.

[Silvertop]

Very, very few people have ever driven a car with a power-to-weight ratio better than 10:1 WITHOUT traction control and 3500+ pounds to keep it planted. So they simpley have no basis on what that an 818 might feel like.

MANY, MANY 818 builders are in for a very rude awakening (suprise?).

Stock 227 horsepower WRX motor is more than enough for a street driven 818.

At this early stage in the 818's life, I guess it's really no difference than trying to choose what to order at the steakhouse - on an empty stomach.

I think you nailed this one right on the head. I hope those who build their 818's with mega horsepower are all very, very, good drivers. They will need to be!

[RM1SepEx]

A good racing or performance driving school is worth its weight in gold. Car control is mostly overlooked by many street drivers. There is a reason for 3 pedals in the car. It is how you use them that makes the differance.

AMEN, can not be understated

I'm involved in www.StreetSurvival.org I highly encourage us, as auto enthusiasts, to get involved. Focus is on emergemncy driving skills and controls for teens, because auto accidents are their highest cause of death. We do not teach new drivers the skills needed to SURVIVE on the streets.

We ALL can benefit from driving school programs, of almost any type...

BTW just helped my nephew last night, scrounged a used oil pan for his 88 BMW325IS. Old lady pulled a "unique move" in front of him and he used the skills he learned from attendance at Street Survival (on my dime...) to avoid a signifigant accident. His "escape route" did include using a curbed area, damaging his oil pan. BUT NO ONE WAS HURT!

[Highway Star]

I have been thinking about this as well. My plan is to go with a stock turbo and tune for drivability rather than max power. I think this is the real demon, getting caught out when the boost kicks in rather than max HP. I could upgrade to my final target of 300 HP easier with tuning the engine rather than replacing it.

Besides, my focus will be on getting the car built and debugging the as-delivered platform. After that, I'll begin tweaking.

[wallace18]

I have been thinking about this as well. My plan is to go with a stock turbo and tune for drivability rather than max power. I think this is the real demon, getting caught out when the boost kicks in rather than max HP. I could upgrade to my final target of 300 HP easier with tuning the engine rather than replacing it.

Besides, my focus will be on getting the car built and debugging the as-delivered platform. After that, I'll begin tweaking.
I think that is a sound idea. This would be a good way to go for a lot of folks IMO.

[timmy318]

I'd like to have two different tunes on my 818. One for best performance when I want to go out on the track and another one that maximizes drivability for everyday use.

[Steve91T]

NA could be built lighter, anyone know how much lighter?

Plus, NA won't have heat issues while on the track.

[tmpst]

I'd like to have two different tunes on my 818. One for best performance when I want to go out on the track and another one that maximizes drivability for everyday use.

There are a lot of aftermarket options for the Subaru that will allow you to do that. If you're a DIY tuner, the Utec system might be of interest. If you're happy with just two maps with an almost instant switch between them, you can look into ecutech. Finally there is the cobb access port, an external accessory that can hold up to 10 maps (iirc) and takes about 30 seconds to reflash the ecu every time you want to change maps.

-t

[tmpst]

Very, very few people have ever driven a car with a power-to-weight ratio better than 10:1 WITHOUT traction control and 3500+ pounds to keep it planted. So they simpley have no basis on what that an 818 might feel like.

MANY, MANY 818 builders are in for a very rude awakening (suprise?).

Stock 227 horsepower WRX motor is more than enough for a street driven 818.

At this early stage in the 818's life, I guess it's really no difference than trying to choose what to order at the steakhouse - on an empty stomach.
I'd like to +1 this. 227 HP in a car that is only 818 kg is *ALOT*. It's the equivalent power to weight of a 500hp Impreza (because the 2wd system will leech less power than the awd system), but it'll actually be harder to drive than a 500hp Impreza since all that power will be going to the rear wheels. I raced a 600hp Impreza and people were always extremely impressed how early and how aggressively I could stomp on the gas coming out of the corners. The 818 is going to be a huge wake up call for anyone used to an Impreza.

I'm a dummy, not taking my own advice, putting ~400hp in the 818R. Before driving it I'm going to re-aquaint myself with RWD by taking a 5-day open-wheel course.

In regards to the OP's question, the EJ254 DOHC Impreza engine is pretty decent (There are multiple Impreza engines out there, the EJ254DOHC is the one you want if you can get it). It has a nice torque curve, and it's very responsive. You'll be at ~175hp untuned and ~200hp lightly tuned, you'll have about the same power-to-weight as the current base model Lotus Elise. Sounds very nice, but you while the Impreza engine in "nice" it doesn't rev nearly as freely at the Toyota 2ZZ-GE in the Lotus. I have a feeling that it might be a bit "boring" as a track engine (I've never taken it on the track), but on the street it should be a great engine.

-t

[Benji]

818lbs? Nice! ;)

[timmy318]

There are a lot of aftermarket options for the Subaru that will allow you to do that. If you're a DIY tuner, the Utec system might be of interest. If you're happy with just two maps with an almost instant switch between them, you can look into ecutech. Finally there is the cobb access port, an external accessory that can hold up to 10 maps (iirc) and takes about 30 seconds to reflash the ecu every time you want to change maps.

-t

Thanks for the info tmpst! I'm gonna check that out now! And don't worry about Benji, we're all human and we all make mistakes!

[tmpst]

818lbs? Nice! ;)oops

[Accro]

I'm a dummy, not taking my own advice, putting ~400hp in the 818R. Before driving it I'm going to re-aquaint myself with RWD by taking a 5-day open-wheel course.

The biggest differences will be 1)Finish your braking before you turn, trail braking doesn't really work in modern open wheel cars. 2)You have to give it a little bit of gas throughout the corner to keep weight and traction on the rear wheels

And for anyone else who's never driven a MR car, NEVER lift or brake while cornering. I mean, if you're going very pedestrian speeds you'll be ok, but if you're even half pushing it's risky. I wouldn't recommend accelerating through the corner if you have a turbo either, cause if it kicks in hard you'll be facing the wrong way.

[Turboguy]

how much is too much?



Well........if I take a detour from shoe-horning in a flat-6, I figure I'll be going for an STi motor with standalone engine management and a turbo anti-lag system.


That isn't too much, is it?

[timmy318]

Well........if I take a detour from shoe-horning in a flat-6, I figure I'll be going for an STi motor with standalone engine management and a turbo anti-lag system.


That isn't too much, is it?

Well, I know nothing of turbos and nothing of Subaru's so you mind helping me out? What are some good turbo anti-lag systems out there???? Also, is it possible to put traction control on the 818?

[Rasmus]

If you can spin the tires from apex to braking point you've got enough.

[Kalstar]

Good point, a way to detune the turbo motor? I have several 600hp cars in my garage and I would be a buyer for such an option. The GTM is a handful at only 380hp, I was planning a tubo set up on my GTM but I am rethinking that. At only 2500 and having no refined power delivery, it is a beast to handle. I have driven several 350hp-450hp GTMs and P/W is up there with my 600hp cars but it is soooooo different in how th car handles the power. Many will have a car that will be as lethal as a loaded gun to an untrained user.

[Mechie3]

You can program the ecu to target a lower boost level.

[flynntuna]

The biggest differences will be 1)Finish your braking before you turn, trail braking doesn't really work in modern open wheel cars. 2)You have to give it a little bit of gas throughout the corner to keep weight and traction on the rear wheels

And for anyone else who's never driven a MR car, NEVER lift or brake while cornering. I mean, if you're going very pedestrian speeds you'll be ok, but if you're even half pushing it's risky. I wouldn't recommend accelerating through the corner if you have a turbo either, cause if it kicks in hard you'll be facing the wrong way.

Very good advice. This is exactly how you had to drive early 911's ,were you coud swap ends without warning. That's why people either loved them or hated them. It will be interesting how the 818's setup tames this tendency, and how it handles at it's limits.

[rjh2pd]

I figure I'll be going for an STi motor with standalone engine management and a turbo anti-lag system.

That isn't too much, is it?

Ha, id like to see an anti lag system on a 2 wheel drive car, much less a 1800 lb 2 wheel drive car. I don't think that it will be necessary as you will be spinning the tires anyway. Granted the anti lag system is very cool, but id think you would be eating through turbos. IF you do it post videos :D

[ccgillett]

Naw the 818 is kilograms, so 1803 pounds. If you run a 200HP NA motor you're at 9:1 (dry, no driver) which is excellent power/weight ratio. Add a 200 pound driver, and 14 gallons of fuel and you're at 10.44 which is still pretty good. A NA will give you good reliability, and of course no turbo lag. Being new to Subaru gear I'm not sure about anti-lag technology: how does it work, and how well does it work?

Supercharging: More horsepower, no turbo lag. Is there a supercharger kit for the NA engine? Does anybody have any experience?

FWIW, I've been driving a Sports Racer this year: 190 horsepower motor, 850 pounds dry. Fuel+car+driver weighs out to 1134 pounds, or an operating ratio of 5.97:1. The thing is insane, you need think way ahead of it. It's very drivable, but suspension setup, tire pressures, and wing configuration are really important to get right. In the 818 people are REALLY going to have to think about suspension setup more than in other FF cars.

I'm completely taken with the design of this car and really want to build one. Based on the Sports Racer experience I will go the turbo route if there's no supercharger available. But for somebody who is doing one of these for the street and who doesn't have a lot of high performance driving experience I would recommend the cheaper, more reliable, and safer NA route.

Everson is finishing the build of my Type 65 coupe, so I have lots of decisions ahead about what to do with that, the 818, etc.

[Nuul]

Hey John, I agree with you. I wonder how many folks are going to build a car with so much power it's more scary than fun.

My opinion is that anything over 300 WHP in this car is undriveable for most people.

[Nuul]

Is there a supercharger kit for the NA engine?

I know of one, but I've not done any research on it to say how well it works. http://www.rs25.com/forums/f14/t97081-gdb-impreza-rs2-5-supercharger-system-s.html

[rjh2pd]

Naw the 818 is kilograms, so 1803 pounds. If you run a 200HP NA motor you're at 9:1 (dry, no driver) which is excellent power/weight ratio. Add a 200 pound driver, and 14 gallons of fuel and you're at 10.44 which is still pretty good. A NA will give you good reliability, and of course no turbo lag. Being new to Subaru gear I'm not sure about anti-lag technology: how does it work, and how well does it work?

Supercharging: More horsepower, no turbo lag. Is there a supercharger kit for the NA engine? Does anybody have any experience?


Subaru doesn't have anti-lag technology for their cars. They and every big rally team do have it. It essentially retards the timing on ignition, maybe when the fuel gets thrown in not sure about that part... but anyway it make the combustion happen when the exhaust valve is open to force a ton of air out of the engine into the turbo making it spool while you aren't moving therefore getting rid of the turbo lag. btw superchargers cant make any more power than a turbo. Normally they make more low end torque, but the turbo will be much better higher up. Also changing the boost on a turbo is much easier than a supercharger.

[Benji]

My opinion is that anything over 300 WHP in this car is undriveable for most people.

I give them half that, at the crank and whilst it will be driveable, the inexperienced without traction control will be finding hedges everywhere if they aren't careful.

See young FR-S/BRZ owners thinking they are good enough to turn off the traction control and the results of that already.

200+ WHP and you better know what you are doing and/or have an EXTREMELY healthy respect for the accelerator pedal.

[Benji]

Is there a supercharger kit for the NA engine? Does anybody have any experience?

There were a few examples at the SEMA Show for the FR-S/BRZ:

http://i23.photobucket.com/albums/b358/benjispics/DSC01139.jpg

Sure it's a different engine but the kit wouldn't be that far off. PhyrraM may know how well the H4's take to being supercharged, though judging by how few kits there has ever been created for the Impreza, I'm guessing it's not that great.

[Mechie3]

I think so few kits were created was because by the time they came out, the WRX was released. Subaru's didn't become all that popular as performance cars until the WRX came, so the 2.5RS from 98-01 was more limited in production.

[carbon fiber]

good to hear voices of reason here. i built a 91 lx mustang for street/track days and it has supercharged351/600rwhp. this was a mistake. the car weighs 3000lbs. and with 3:27 rear gears and i can still break the tires (285's) loose with a roll on at 100mph. coming off turns hard was a handful. it's a blast for a while (in a straight line)and then after that becomes more of a pain in the a** than fun. i took off the supercharger and it's drivable again. traction control on cars this light are a great idea. lots of the gtm guys are running race logic or some other form of traction control. i've heard great things about the racelogic, it's what i'm going with.

[timmy318]

good to hear voices of reason here. i built a 91 lx mustang for street/track days and it has supercharged351/600rwhp. this was a mistake. the car weighs 3000lbs. and with 3:27 rear gears and i can still break the tires (285's) loose with a roll on at 100mph. coming off turns hard was a handful. it's a blast for a while (in a straight line)and then after that becomes more of a pain in the a** than fun. i took off the supercharger and it's drivable again. traction control on cars this light are a great idea. lots of the gtm guys are running race logic or some other form of traction control. i've heard great things about the racelogic, it's what i'm going with.

Well, now I'm done with my search for a good traction control system thanks to you! Now on to find some other little goodies :p

[carbon fiber]

check out that isis wiring system also, i love the idea of never having to trace wiring problems again. the guy who developed that should get the nobel!

[timmy318]

check out that isis wiring system also, i love the idea of never having to trace wiring problems again. the guy who developed that should get the nobel!

Already on my list! :D

[Benji]

good to hear voices of reason here. i built a 91 lx mustang for street/track days and it has supercharged351/600rwhp. this was a mistake. the car weighs 3000lbs. and with 3:27 rear gears and i can still break the tires (285's) loose with a roll on at 100mph. coming off turns hard was a handful. it's a blast for a while (in a straight line)and then after that becomes more of a pain in the a** than fun. i took off the supercharger and it's drivable again. traction control on cars this light are a great idea. lots of the gtm guys are running race logic or some other form of traction control. i've heard great things about the racelogic, it's what i'm going with.

Something about "It's more fun to drive an underpowered car hard, than an overpowered car easy."

[carbon fiber]

absolutely.

[mrvwcastner]

I drive an almost stock 1.6 engine Miata with a lot of chassis work & race tires. I'm predictably faster than the less experienced vette drivers & equally fast as the lotus elis cars with no mods on race tires & descent drivers. Point being if we get very used to the 818 in either model with a descent NA motor we will be very competitive. I will be trying to finish my 818R with a well tuned NA motor (days worth of porting polishing & trimming will not only free up lots of power, but reduce weight). I would love 250 to 300 HP NA. I'm unfamiliar with subbie motors not sure how realistic this is.

[apexslider]

There are a lot of aftermarket options for the Subaru that will allow you to do that. If you're a DIY tuner, the Utec system might be of interest. If you're happy with just two maps with an almost instant switch between them, you can look into ecutech. Finally there is the cobb access port, an external accessory that can hold up to 10 maps (iirc) and takes about 30 seconds to reflash the ecu every time you want to change maps.

-t

go with the Cobb Access Port. Utec is really only good if you want open source. Cobb has a number of solid off the shelf maps to do daily driver, and allows for a custom tune for track. Plus Cobbs customer support is some of the best you will find. I had a custom set up and they bent over backwards to make sure I had a solid tune and was happy with it.

I currently have an STi running about a 6.4 p/w, and it is stupid fast. I think that would be around a 3.6 p/w in the 818 (probably less because the motor wouldn't lose as much with 2wd)... I couldn't imagine driving that on the street. Maybe on the track with R compounds, but even then, things could go very wrong very quick. I think a WRX motor with a Vf39 turbo would be the biggest I would go for usable power

[tmpst]

I drive an almost stock 1.6 engine Miata with a lot of chassis work & race tires. I'm predictably faster than the less experienced vette drivers & equally fast as the lotus elis cars with no mods on race tires & descent drivers. Point being if we get very used to the 818 in either model with a descent NA motor we will be very competitive. I will be trying to finish my 818R with a well tuned NA motor (days worth of porting polishing & trimming will not only free up lots of power, but reduce weight). I would love 250 to 300 HP NA. I'm unfamiliar with subbie motors not sure how realistic this is.

I would have thought that would cost you a fortune, but...

Here's a recent EJ25 NA build that reached 204 AWHP on 100 octane. That's not far from 300 at the crank...

http://forums.nasioc.com/forums/showthread.php?t=2362779

I wonder how much he spent...

[soul strife]

No doubt a turbo. Coming from a procharged Trans AM the n/a will feel slow. I'm going with a tuned normal WRX and will leave it there. I am not sure how much power they gain with a simple tune but I'm sure it will be enough.

[mrvwcastner]

I've owned lots of turbo VW cars including an authentic yet highly modded Callaway rabbit GTI & my simple NA Miata 1.6 is the fastest autocross I have owned so far. Mainly due to growing up driving different & realizing paying a race instructor to sit shotgun for a couple of days is well worth the money instead of whatever bolt on mod I could have ordered. I would love an EE20 diesel motor to be unique, but basic NA will do me fine. As is usual with me a 2nd motor on a stand being slowly built to my spec will accompany but may be very long time before it goes in. All my turbo cars were fun, but my built NA GTI Eurospec was most predictable & close 2nd to Miata on the track. My experience is $ per HP boost is cheaper, but always less predictable & in the end costs more when you account for hidden costs be it clutches, pistons, tires or bail money & tow trucks. I know I have spent lots on all!

[Benji]

No doubt a turbo. Coming from a procharged Trans AM the n/a will feel slow. I'm going with a tuned normal WRX and will leave it there. I am not sure how much power they gain with a simple tune but I'm sure it will be enough.

Out of curiosity, how much did your procharged Trans AM weigh....

[armstrom]

I just wanted to clear up some things regarding anti-lag. In general, the previous description of anti-lag is correct. It creates positive manifold pressure without the engine being under load by "spooling" the turbo artificially. Turbo boost pressure is directly related to the rate at which air mass passes through the engine. At low RPM and low engine load, there isn't enough additional flow from the turbo to create a positive manifold pressure. High RPM alone won't do it because a revving engine that isn't under any load still doesn't move enough air mass quickly enough to spool the turbo enough to overcome the increase in intake air demand and produce (significant) positive pressure.
So, all anti-lag systems create an artificial excess of exhaust gas flow rate by allowing some of the combustion process (namely the rapid expansion that occurs when igniting the air-fuel mixture) to take place inside the exhaust manifold rather than in the combustion chamber. That means the additional force from the expanding charge can be used to directly spin the turbine section without imparting much force on the pistons as it would if it were occurring in the combustion chamber as it should.

There are two primary ways this is accomplished. The first involves manipulating the fuel injector duty cycles and ignition timing only. In other words, it doesn't require any additional equipment on the engine, just engine management programming. First injector duty is increased beyond what would normally be required for the current load cell. This introduces excess fuel into the chamber. Next, the ignition timing is severely retarded. This ensures that the exhaust valves are open (at least partially) and the air/fuel charge is flowing into the exhaust manifold before all of the extra fuel can be burnt. The flame front then follows the charge out into the exhaust manifold where the combustion continues. This produces a pressure surge in the exhaust manifold spooling up the turbo giving you boost without load. This type of system may also employ a type of rev-limiter that skips ignition events allowing an unburnt charge to be ignited in the manifold by the subsequent "good" ignition event. These types of systems have obvious drawbacks. You're now abusing the combustion chamber with unburnt fuel, that means carbon buildup on the back of your valves, eating spark plug electrodes and of course, significant increase in EGTs and unpredictable pressure surges slamming into the turbine wheel of the turbo. This eats turbos and generally damages the mentioned components...
The other type of system is much more rare but works in a very similar way. But rather than playing games with ignition timing and injector duty cycle air and fuel is injected directly into the exhaust manifold on demand. Same net results but with more control. Obviously, this is not something you get for free by installing a stand-alone EMS...

So, when is this used? There are two situations, one is more of a launch control type situation. The car is sitting still at the line and you want to launch the car with full boost. You hear this at the start of every WRC race. The revs go up, the car starts to miss ignition events and it sounds like a machine gun just before launching itself around the course. The other situation where anti-lag is used is during shifts. The system allows you to "stay on boost" during the low load time experienced by the engine during shifts. Normally you see this as a type of flat-shifting. The driver keeps the gas pedal buried, depresses the clutch (which enables the flat-shift anti-lag mode in the ECU) and shifts gears. This is also done in WRC races but is not as obvious since the sequential gearboxes they use shift so quickly.

[Nuul]

Good explanation Armstrom, thanks for posting that. On the topic of flat foot shifting: anyone know if that is something you can do with an open source tune or is it specific to Cobb?

[armstrom]

I'm not too familiar Subaru ECU tuning but you can usually get a decent "anti-lag" effect with any rev-limiter. The trick is if the ECU tuning allows you to drop the rev limiter to a lower level in response to an external signal (clutch interlock switch). If the ECU already has access to that switch signal and it can be used to control the rev limit, then you can probably get something reasonable setup. The fact that COBB offers launch control indicates that the stock ECU already has access to that signal.

[soul strife]

Out of curiosity, how much did your procharged Trans AM weigh....

3400# 3600 Stall and sticky tires.

[Benji]

So at nearly half the weight you'd probably be surprised at half or a third of the power you are probably putting out now...

[jlahl3160]

See revision to first post on this thread for revised table.. hopefully it is easier to read..
added some additional models.. corrected some data.

John.

[C.Plavan]

I would be happy with 250-300hp. I have been racing for years (911's, BMW's, Mazda's). People who have never raced before will be in for a big surprise.

My vintage (1969) 911ST race car has 211HP at the rear wheels (2.5L Short Stroke) and the car weighs in at 2083 pounds with me in it. It is a blast to drive. It can beat up on cars with almost 3 times the HP in the corners. This is a car with Torsion Bar suspension and 43 years old! I can't wait for the 818R to arrive so I can start building. This thing should be a agile trackstar on "new coilover" suspension!

Here is a in car video example of 9.87 pounds per HP on the track (211 RWHP/2083lbs) Enjoy!
https://vimeo.com/29012828


https://vimeo.com/29012828

[philly15]

Subaru doesn't have anti-lag technology for their cars.

im like 99% sure the 02 wrx ecu can be programmed to run anti lag, also as stated before you can also run launch control i think the only issue is other than the 02 ecu you cant change it its set at one specific rpm had two 02 wrxs and one 03 in the 02's we could set the launch control at any rpm in the 03 it could only be set at 5300 rpm

[wallace18]

Great piece of driving. Makes me miss my old IMSA days.

[metalmaker12]

Turbo, why even think na in these reliable turbo engines

[Wayne Presley]

++I have a Factory Five roadster with 705 RWHP and assuming a 15% powertrain loss thats 830 flywheel HP. The car weighs 2521 full of gas so the power to weight about 3.03 lbs/hp. And it's really too much to put to through the 315 Nitto NT05 drag radials as it freewheels in first at will, second at any rpm above 2000 and lights them up at 85 mph. I also have in my shop a Lotus Elise with a Garrett GT3071R, running 340 rwhp and it weighs 1941 on my scales. 15% = 400 FWHP and 4.85lbs/hp. It is really fun to drive and only spins the tires hard in first gear. I have a couple of in car videos showing a 2nd - 4th gear 20-120mph and 0-100. If anyone wants to see them, pm or email me for links.

[jlahl3160]

Thank you for sharing the video I loved it. Good car great driving.. success!

I believe I posted the chart to keep my plans realistic. I do not plan on building the 818R... And if I were, the question of how much HP would not have entered my mind... in racing more is always better. For me, at this point in my life, a car that is quicker than a Z4 is probably good enough.

I know I would be very happy with faster... However I know I would use it if I had it. And I could get in big trouble in under 4 seconds... that is not to say I won't get into trouble under 6. :o

The other part of this is not for me to suggest what you should or should not want... but to bring up the point that one should think about the plan... What effort do I want to put into this, how much money will it take, and of course, how much HP do I want? Based upon how many have put in pre orders, about 80% will be building 818S. It may be worth thinking about ... or not I though it was.

John


I would be happy with 250-300hp. I have been racing for years (911's, BMW's, Mazda's). People who have never raced before will be in for a big surprise.

My vintage (1969) 911ST race car has 211HP at the rear wheels (2.5L Short Stroke) and the car weighs in at 2083 pounds with me in it. It is a blast to drive. It can beat up on cars with almost 3 times the HP in the corners. This is a car with Torsion Bar suspension and 43 years old! I can't wait for the 818R to arrive so I can start building. This thing should be a agile trackstar on "new coilover" suspension!

Here is a in car video example of 9.87 pounds per HP on the track (211 RWHP/2083lbs) Enjoy!
https://vimeo.com/29012828


https://vimeo.com/29012828

[2FastCobra]

Stay with a turbo, superchargers really heat up the air. I have run roots and centrifugal type superchargers for years and they are no match for a properly sized turbo set-up with good gearing. My FFR roadster is north of 1000rwhp and weights 2260lbs without me in it and a quarter tank of gas. Don't be afraid of making to much power, just take the time to get the suspension set-up with good drag radials the 818 should really move!!! A friend of mine down the road just put one on order. I am sure he is planning on some major power mods to his. Good luck

[2FastCobra]

Here is a video of my car on the dyno. http://youtu.be/u9CoxEh-eig

[mobius]

Stay with a turbo, superchargers really heat up the air. I have run roots and centrifugal type superchargers for years and they are no match for a properly sized turbo set-up with good gearing. My FFR roadster is north of 1000rwhp and weights 2260lbs without me in it and a quarter tank of gas. Don't be afraid of making to much power, just take the time to get the suspension set-up with good drag radials the 818 should really move!!! A friend of mine down the road just put one on order. I am sure he is planning on some major power mods to his. Good luck

YES I AM! haha

You didn't miss anything at the track tonight. timers were messed up so only giving 1/8 times.

[2FastCobra]

Most people don't believe that you can hook up that kind on power with out massive tire spin until they take a ride in it. I think an 818 with 550+ hp power should be a blast on street and track. Sorry that I could not make the track tonight , I promised my wife I would take her out for her birthday.

[mattfra]

2FastCobra I can vouch for your above comments!! I was down to visit my brother who retired from the USAF there at Moody AFB. My brother 'happens' to be neighbor to "2FastCobra". He pulled out the Cobra after working and all day and was gracious enough to show us his car. Then he offered to take me for a ride! Ever since watching Gumball Rally on tv when I was a kid I have loved Cobras. I've been around fast cars most of my life. Had a buddy with a 1965 'Vette Roadster, factory knockoffs, close ratio 4 speed 3.36:1 rear AND a torque monster 502 crate big block. That car was fast!! Another friend with a low 13 sec Nova, Chevy II's, etc...Even my old 67 Chevelle 283 with fuelie heads was pretty quick! My current 1965 Cyclone project is no slouch with a 289.
Then I rode in '2FastCobra's" car... Absolutely no comparison. His car flat out HOOKS and goes!!! It's the fastest car I have ever ridden in.
We got out on the main street (in an un-named town...LOL) and got rolling about 30mph or so and he stuffed it. I'm not even sure what gear he was in. The rate of acceleration (read NO wheel spin) was actually disorienting. I hear him say loudly "120!" meaning 120mph then backed off of it. 14lbs of boost instantly. Hooking and pulling HARD! Absolutely amazing. No turbo whine. The car rides like a Cobra should - firm but not jarring. He has built this car to be so well engineered it's incredible. We then turned onto a country road and hit 110 immediately. The car handles like it's on rails. You can actually talk to each other at 100mph without yelling ...it's that mellow. It's a BAD machine!!!!!!!!
Thanks AGAIN!!!

Here's a quick vid of us pulling out of the driveway...
http://i48.photobucket.com/albums/f231/mattfra/th_MVI_3726_zps1e1f581d.jpg (http://i48.photobucket.com/albums/f231/mattfra/MVI_3726_zps1e1f581d.mp4)

http://s48.photobucket.com/user/mattfra/media/MVI_3726_zps1e1f581d.mp4.html

[mobius]

That's cool no worries!

I would love to do around 500whp on the 818 just waiting till they figure out the transmission... As of now I am going aftermarket edu probably Haltech as that is what i am running in the vette and it is pretty sweet. Ill add a racepack style dash and ISIS wiring to simplify everything. Then whatever power i can get without grenading the tranny everytime i take it out...

[mattfra]

Not sure where my post went??...but I'll repost.
I got to ride in 2FastCobras car. It's quick and it hooks. My brother who just retired from the USAF is neighbor to him.
He offered a ride. I accepted! Quick. Disorientingly quick.:cool:
He ran it up to 14lbs of boost (about 120). Whew. You can actually talk to each other at 100mph! Car rides like it's on rails.
Not harsh.

http://s48.photobucket.com/user/mattfra/media/MVI_3726_zps1e1f581d.mp4.html

[THE ITALIAN]

Nice to see some conservative thought process here. I had a Turbo Porsche, it would scare the hair out of your nostrils when the spooling began. Wayne, well that is Wayne, he has a crazy crazy roadster and a conversation piece + drag racer ( I think it turned 10's if not mistaken) - that's neat, but most of us will use our cars for other reasons.
Anything "spooling" with big HP can be frightening and steal your confidence while wetting your passengers G string (male or female)(in your case male)
I think tuning will be the final work to make these cars drivable and fun. Low boost and early is a good way to go.
My roadster is around 300 hp and it is more than enough with frame mods that turned it into a slot car (but rides like a truck even with IRS) My passengers usually laugh when we hit the curves, it is fun and pops out like lightening without sliding, this is what you want.
I can see a 280 Hp 818 eating a 500 Hp 818 in the twists
I am still waiting to see how many burn 3rd gear with the new configuration on the transmission. Maybe something about this ???

[Canadian818]

Didn't dave mention that they were going to be figuring out how to run the 6spd in their 818R after it blew 3rd gear? Or maybe it was implied.

[EricScottZehnder]

We should probably revise the figures as we know it weighs several hundred pounds more with fluids and driver in it. Call it 2000 pounds to make it easy to calculate.

I never seriously thought about going higher than 300hp. I'd like to go with a reliability oriented turbo setup and start at a reasonable boost level. I would hope I could get 250hp with that with the option to turn up the boost and get a bit more. Looking at around 7-8lbs per HP which is very quick.

[Silvertop]

My moderately tweaked 2.5 NA will likely be generating between 200 and 210 flywheel horsepower based on the mods I have made. And I expect that to be fast enough -- in fact, I expect it to be just the right amount of fast -- at least for me.........!:)

[Oppenheimer]

Thats right in the magic 10lbs/hp range, or just a little lower, which is perfect for a balanced car that is drivable. Especially being NA. What are your mods, and what was the cost?

It seems like there is this annoying gap between 165 hp NA 2.5 and over 227 hp 2.0 turbo that skips right over the sweat spot (for fun street car you want to use all the time). Goldilocks Syndrome. This one too small, that one too big.

[RM1SepEx]

to each their own... I also feel that 10 lbs/hp is perfect, but it needs to be loaded lbs and at the wheels, so I'm shooting for 220-230 WHP

someone wants 500, good for them, too much for me as an old fart with slow reaction times and absolutely no desire for ANY electronic aids!

[Xusia]

Thats right in the magic 10lbs/hp range, or just a little lower, which is perfect for a balanced car that is drivable. Especially being NA. What are your mods, and what was the cost?

It seems like there is this annoying gap between 165 hp NA 2.5 and over 227 hp 2.0 turbo that skips right over the sweat spot (for fun street car you want to use all the time). Goldilocks Syndrome. This one too small, that one too big.

EZ30 man!!

[Silvertop]

Thats right in the magic 10lbs/hp range, or just a little lower, which is perfect for a balanced car that is drivable. Especially being NA. What are your mods, and what was the cost?

It seems like there is this annoying gap between 165 hp NA 2.5 and over 227 hp 2.0 turbo that skips right over the sweat spot (for fun street car you want to use all the time). Goldilocks Syndrome. This one too small, that one too big.

My mods:

Techworks Engineering Stage II Camshafts with Heavy Duty Springs
Grimmspeed Ported/Polished/ Ceramic Coated Intake Manifold
Grimmspeed Lightweight Crank Pulley
Techworks Engineering Stainless Steel EL headers (Ceramic Coated), High Flow Cat & Muffler
Level 3 ECU tune by Delicious Tuning
Air Intakes yet to be determined
Exedy Lightweight Flywheel w/ Stage 1 Clutch
Quaife Limited Slip Differential (ordered)

How much did it cost? Too dang much! I'm kind of afraid to add it all up. But it's in excess of $4500 for the mods listed. It would have been significantly cheaper to have started with a WRX donor and then simply left it stock. And it would have been faster. But I didn't go NA to save money. I wanted the predictability of the NA engine, along with the broader torque curve, and I just like the relative simplicity of a naturally aspirated engine . Also, I know in my guts that if I had gone with a WRX donor, I still wouldn't have been able to resist tweaking it -- so I probably would have spent the extra money anyhow.

And I completely agree with your idea about the power "Sweet Spot". I think it's going to be very drivable, but still plenty fast -- certainly faster than anything I've ever owned -- or driven. I'm betting that it gets me to 60mph in 5 seconds or less. It'll sure be fun finding out!:)

[Ravendas]

I'm not too familiar Subaru ECU tuning but you can usually get a decent "anti-lag" effect with any rev-limiter. The trick is if the ECU tuning allows you to drop the rev limiter to a lower level in response to an external signal (clutch interlock switch). If the ECU already has access to that switch signal and it can be used to control the rev limit, then you can probably get something reasonable setup. The fact that COBB offers launch control indicates that the stock ECU already has access to that signal.

There's a couple of ways to go about it. Personally, I'll be using the CarBerry speed density rom (http://www.romraider.com/forum/viewtopic.php?f=36&t=7594), which offers quite a few features such as anti-lag, no lift to shift, launch control, etc. CarBerry's only for '02-03 WRX, though, because they have the 16-bit ecus. There's a project to do 32-bit ecu with speed density, but I haven't been following its progress.

[THE ITALIAN]

[QUOTE=RM1SepEx;117385]to each their own...
too much for me as an old fart with slow reaction times and absolutely no desire for ANY electronic aids![/QUOTE
I hear Ya ! My wife is 17 years younger than me
What ? Did I write that out loud ?

[FormerFF]

I think I'm missing something here on the driveability of the higher horsepower cars. My frame of reference is that I used to drive a Formula Ford in SCCA. These cars typically have 113- 115 hp, and come off the track weighing 1105 lbs including driver, right around 10 lb/hp. They do have a nice gradual torque curve, and modest (7.5 inch) slicks, so that helps, but we always considered them to be low powered cars, and drove them accordingly. Really, the only formula car we considered to be powerful were the Formula Atlantic cars, with roughly half the power to weight ratio, but a lot more grip. I would think that either of the stock turbomotors would be fairly tractable and shouldn't be too much of a handful for most drivers. I can certainly see if you've built a high boost engine with a lot of turbo lag that it could easily catch the driver out. Other than that, I'm not seeing that many of the people who would be driving an 818 would have a problem with a power to weight ratio of 8 or so.

Maybe I'm missing something, if so, please let me know,

[Xusia]

Hi FormerFF and welcome!

To answer your question, I don't think anyone is talking about stock engines when discussing drive-ability - they are all talking about modified engines. It's fairly easy to get 350-400 hp out of WRX engine with reasonably priced mods. To illustrate the concern some have, let's use the example of a 400hp engine in an 1800 lbs car with a 200 lbs driver. That equates to only 5 pounds per hp. Furthermore, to get to 400 hp, you almost assuredly need a larger turbo pushing more boost, which more often than not means that power comes on in a surge at some point. So the concern is the surge of power in such a light car, with [for the hp] limited tire width. I could see it being a handful...

[FormerFF]

Hi FormerFF and welcome!

To answer your question, I don't think anyone is talking about stock engines when discussing drive-ability - they are all talking about modified engines. It's fairly easy to get 350-400 hp out of WRX engine with reasonably priced mods. To illustrate the concern some have, let's use the example of a 400hp engine in an 1800 lbs car with a 200 lbs driver. That equates to only 5 pounds per hp. Furthermore, to get to 400 hp, you almost assuredly need a larger turbo pushing more boost, which more often than not means that power comes on in a surge at some point. So the concern is the surge of power in such a light car, with [for the hp] limited tire width. I could see it being a handful...

Thanks. I can certainly see that a 300 hp engine with a spiky powerband could have some drivers swapping ends in a hurry. Some others may be surprised by how a rear mid engined car responds, I know the first time I drove a Formula Ford it intimidated the heck out of me. As always, it's best to find out how fast you can go by sneaking up on the limit rather than charging ahead.