Displacement/Torque to weight ratio

[Gollum]

I'd just like to put this into perspective for those out there that might look at the Subaru power plant as a "small 4 banger" or think that being a 4 cylinder turbo assume that the 818 will have a hard time getting out of the hole.

All this talk about turbo lag and such, though warranted, is kind of getting to me.

So let me ask a question to all the roadster kit owners or those that think 2.5 liters isn't enough to be "torquey". How much do you feel the "pull" of a city bus?

Those have loads of torque, but they're extremely heavy.

Next question. Is it impossible for a bike to feel torque despite the small displacement?

I'd answer no. I'd even say that most bikes feel MORE torquey than most sports cars.

So here's my point I'm going to sit on. It's all about torque to weight ratios. And another thing to realize, is that in NA form, torque is directly limited by displacement. A good rule of thumb is that it's incredibly easy to reach 70 ft.lbs. per liter. That puts a ford 5.0 at 350 ft.lbs. which is entirely doable. So putting power or torque to displacement aside, let's look at some pure displacement examples.

The 2011 Mustang GT, weighs in around 3533 pounds and has 5 liters. That's around 706 pounds per liter of engine you have.

The Elise at around 1900 pounds, with a 1.8 liter engine is around 1050 pounds per liter.

The 2011 Hemi Challenger is roughly 4200 pounds and at 6.1 liters is arond 690 pounds per liter.

The 818, at 1800 pounds with the 2 liter engine is at 900 pounds per liter, and with the 2.5 is at 720 pounds per liter.

So you see, even WITHOUT boost, the 818 should feel as torquey as most of the modern muscle cars and even better than the lotus.

Obviously even with the 2.5 liter it'll never compare to the feeling of 351W or larger V8 in a tiny %obra replica.

But let's think about it this way. Even with a mild 300hp, off boost the 818 will feel like a muscle car, and then on boost will feel like one of the most wicked 427 %obras you could imagine. And some more numbers:

So at 2.5 liters, you can expect around 180+ foot pounds of torque available off idle. And considering it's DOHC design, it'll have much more than that at torque peak in NA trim. But with boost you can expect peak torque numbers to reach 350 ft.lbs.

No matter what way you slice it, it's going to be fast. I know some of you are used to cars with very impressive power/weight ratios. But I just want people to shed this idea that the car won't be fun off boost, or that getting boost will be a problem. It won't be a problem. Imagine a 600+hp turbocharged mustang. It's not going to require boost to get off the line easily, or take much to pass someone on the freeway. A stock mustang can easily reach 100mph on an onramp. Turbocharge it and it'll reach aerodynamic limits with ease.

And so ends my little rant. :-D

[2KWIK4U]

Well put,

I deal with turbo engines everyday and one thing I can tell you is the spool up should not be a big problem in this case. The projected engine should be a great fit for this project and quite capable of outer limits in horse power if you so choose but the torque will be sufficient to get it moving rapidly.

[LifeIsOnTheWire]

you dont have to convince me, but well put.

if anyone has any concerns in this regard, spend some time browsing some Honda forums like Honda-Tech. lots of guys turbocharge the honda B-series engine. its a 1.6-1.8L with pathetic torque. but in a 1900lb chassis, they can give 911 Turbos a run for their money.

ive had a few Hondas over the years, my last civic hatch weighed 1975lb, and was NA (honda k24), it made 295whp, and 202ftlb. even with that low of torque it could still run 12's in the 1/4mile.

[Wilky]

In the UK they have 4 versions of the Lotus Elise, the most popular sold is the least HP version with 139 HP

[Ks2]

even as far as turbo lag is concerned, the stock (or stock sized turbo) spools fast the top mount intercooler doesn't have alot of piping, even a medium sized turbo and front mount and you still will spool quick, unless you are running a enormous aftermarket turbo you should have no problems spooling the turbo

the big advantage for me of these motors is off boost you can still manage great fuel economy and on boost they can run with cars twice the displacement (im talking about a 3500+ AWD subaru, in a 1800 pound car that isn't AWD you will put way more of that power down)

[LifeIsOnTheWire]

In the UK they have 4 versions of the Lotus Elise, the most popular sold is the least HP version with 139 HP

true. even more so, the first Lotus Elise had 118hp. but back then it weighed 1600lb

now Hennessey is putting a 1200hp twin turbo V8 into an Elise chassis (a stretched chassis, mind you).

[JRL]

In the UK they have 4 versions of the Lotus Elise, the most popular sold is the least HP version with 139 HP

Most likely a function of almost $9 a gallon for gasoline and crazy taxes.

[Gollum]

There's definitely a market for "supercars" that are also "supersavers". I'm definitely in that camp to a degree. I don't mind a car that gets 7mpg if it's worth the fun, but it's not going to get a ton of use. While if I owned a lotus I'd drive it every day because it's no cost prohibitive.

The 818 should fit that niche nicely. I'm better a good tuner that's not too concerned about max power will be able to see 50mpg in this thing with the right setup. Obviously there'd be sacrifices, but for some it's worth it.

[Ks2]

50 might be a stretch... 25-30 off boost and driven sanely... these engines run on E-85 rather well and has the potential for alot more power due to it's higher octane (with a hit to MPGs of course)

[Gollum]

I don't think 50 is a stretch, it just depends on the owner. A CRX HF will hit 45-50 in most people's hands, but in the hands of someone driving with max MPG in mind they'll go over 55 easily. Add some minor aero mods and it'll do 65mpg.

It's all in the person and the prep of the vehicle. The 818 could make a wonderful daily driven super car in that regard. Even with hard tires it's still going to corner well. Most people won't take it to 170+mph so huge downforce isn't needed.

I'm not saying it wouldn't take a lot of work, just saying it's possible. But as we all should know, factory subaru tunes are outrageously rich and just retuning the stock engine will make more power and get better MPG. I'd say most people with a good tune will be able to hit 30mpg on the highway, as long as they don't get into too many grudge matches.

[thebeerbaron]

Gollum - I don't know if you saw this thread (http://thefactoryfiveforum.com/showthread.php?1147-What-does-818-mean) about weight, but it's a parallel to what you're going for here. Maybe a nice table with the Torque/weight ratios of a couple of 818 iterations alongside a few modern sports cars would be in order. I suggest using the "code" tags as described in that thread to get things right. Let me know if you want a hand.

As far as your mileage - I'm afraid that with the aerodynamic properties of a roadster, 50mpg is going to be a dream. Maybe if this thing comes with a hard top and the design is slippery, but honestly I'm not sure how much effort can or will go into giving the body a low CoD or whatever. I think it could probably do well on the highway, but I doubt too many people will end up driving it there. 1800lbs will get bounced around like nobody's business with the semis and rough pavement of our highways.

[Gollum]

The CRX mentioned is around the same weight... That doesn't have much to do with preventing a car from getting good mpg.

Yes a roadster model might not be as aerodynamic, but we've all pretty much gathered that we want there to be a hard top version.

I've seen a lot of cars that started in the 30mpg range make it up to 50 when done and used right. I wasn't saying that everyone could do it, or that many will, just the mere possibility that someone who wanted to could.

And maybe I will do up a nice table like that for this topic. Thanks for the input.

[readymix]

Car / Stated HP / Price / Pounds Per HP / Ignore this number, it's some points system from the post i stole this from...

Acura TSX=205 / $29000 / 15.7 / 455
Acura TL=286 / $39000 / 12.6 / 491

Audi TT=255 / $40000 / 10.9 / 436
Audi A3=250 / $34000 / 12.9 / 438
Audi RS4=420 / $66000 / 8.6 / 567

BMW 3 Series=300 / $41000 / 10.9 / 446
BMW Z4=330 / $51800 / 9.1 / 464

Bugati Veyron 16.4 =987 / $1,200,000 / 4.2 / 5040

Buick LaCrosse=240 / $29000 / 14.5 / 476
Buick Lucerbe=275 / $35000 / 13.6 / 420

Cadillac CTS-V=400 / $51000 / 9.2 / 469
Cadillac STS-V=469 / $77000 / 8.2 / 631

Chevy Cobalt SS=205 / $22000 / 13.5 / 297
Chevy Corvette C6=400 / $45000 / 7.95 / 357
Chevy Corvette Z06=505 / $70000 / 6.3 / 441
Chevy Impala SS=303 / $28000 / 11.7 / 327
Chevy Malibu SS=240 / $25000 / 13.2 / 330
Chevy Monte Carlo SS=303 / $28000 / 11.0 / 308
Chevy Trailblazer SS=395 / $33000 / 12.0 / 396

Chrysler Crossfire=215 / $40000 / 14.0 / 560
Chrysler PT Cruiser=230 / $29000 / 13.3 / 385
Chrysler 300C SRT-8=425 / $40000 / 8.7 / 348

Dodge Caliber SRT-4=300 / $24000 / 9.8 / 235
Dodge Charger SRT-8=425 / $36000 / 8.9 / 320
Dodge Viper SRT-10=510 / $84000 / 6.7 / 562

Ford Mustang GT500=500 / $41000 / 6.7 / 274
Ford Mustang GT=300 / $28000 / 11.5 / 322

Honda S2000=237 / $34000 / 11.9 / 404
Honda Civic Si=197 / $24000 / 14.6 / 408

Hyundai Tiburon=172 / $20000 / 17.3 / 346

Infinite G35=315 / $35000 / 11.1 / 388

Jeep Grand Cherokee SRT-8=425 / $40000 / 11.2 / 448

Lexus IS350=306 / $35000 / 11.3 / 395

Lincoln MKZ=263 / $35000 / 12.9 / 450

Lotus Elise=190 / $43000 / 10.4 / 447
Lotus Exige=243 / $80000 / 8.1 / 648 (Not street legal)

Mazda MX-5=170 / $28000 / 14.35 / 401
Mazda RX-8=238 / $28000 / 12.7 / 355
MazdaSpeed3=260 / $24000 / 10.3 / 247
MazdaSpeed6=287 / $30000 / 11.1 / 333

Mercedes CLK=475 / $85000 / 7.5 / 637

Mini Cooper S=175 / $25000 / 14.5 / 362

Mitsubishi Evo XI=286 / $35000 / 11.18 / 391
Mitsubishi Eclipse=260 / $29000 / 14.1 / 408

Nissan Altima=365 / $30000 / 11.5 / 345
Nissan 350Z=315 / $42000 / 10.6 / 445

Pontiac Solstice GXP=260 / $26000 / 11.5 / 299
Pontiac G6=252 / $29000 / 13.4 / 388
Pontiac Grand Prix=303 / $28000 / 11.4 / 320

Porche Boxter S=295 / $65000 / 9.7 / 630
Porche Cayman S=295 / $70000 / 10 / 700

Saleen S7 Twin Turbo=750 / $600000 / 3.9 / 2340

Saturn Ion=205 / $21000 / 13.4 / 281
Saturn Sky=260 / $29000 / 11.2 / 324

Scion tC=161 / $17000 / 18.0 / 306

Subaru STI=293 / $33000 / 10.3 / 339
Subaru Legacy=250 / $34000 / 12.2 / 414

VW Jetta=200 / $24000 / 16.1 / 386
VW GTI=200 / $23000 / 15.8 / 363

Volvo V50=218 / $35000 / 14.8 / 518
Volvo S60=300 / $36000 / 11.6 / 417
Volvo V70=300 / $37000 / 10.98 / 406
Volvo S80=311 / $45000 / 11.2 / 515


Assuming a final weight of 1800 lbs on the 818:

FFR-818 w/ Standard 2.5RS/i donor = 165hp / 10.9 lbs per hp
FFR-818 w/ 2.0L WRX donor = 227hp / 7.92 lbs per hp
FFR-818 w/ STi 2.5L donor = 300hp / 6 lbs per hp
FFR-818 w/ Built 2.5L motor (using my setup as example) = 400hp / 4.5 lbs per hp

For reference:

Formula 1 cars have about a 1.6 lbs per hp ratio
Koenigsegg CCXR 2.8
NASCAR 3.7
Ferrari F430 6.6

[crackedcornish]

something you guys might find interesting
http://www.060calculator.com/

[Oppenheimer]

I had a CRX HF, and it weighed a whole lot less than 1800 lbs. It was a fun car, got insane mileage that even a Prius has trouble achieving.

I plan on driving my 818, once it comes out with a top, as a commuter most days that aren't in winter. I won't need insane HP, I'll be one of those that Gollum is refering to, though ultimate fuel mileage won't be my concern. But I am hoping for >35 mpg highway, driven 'normally'. I don't see why that would be difficult to achieve.

[Wilky]

I am really interested in doing a 2.5 n/a engine at first until I can get/build a turbo one. there are a lot more n/a engines available from subaru

[StatGSR]

So here's my point I'm going to sit on. It's all about torque to weight ratios. And another thing to realize, is that in NA form, torque is directly limited by displacement. A good rule of thumb is that it's incredibly easy to reach 70 ft.lbs. per liter. That puts a ford 5.0 at 350 ft.lbs. which is entirely doable. So putting power or torque to displacement aside, let's look at some pure displacement examples.


I feel your assumptions are a little too dumbed down, compression ratio and efficiency will also have a large part to do with what kinda torque can be made with a four stroke engine, the problem with boosted cars is that when off boost they don't have the CR to make great torque. (this should be the larger fear for most thinking torque will be an issue)

Now i completely agree that the ej25 with a stock gear box/tire size will feel like a fantastically torquey motor in the 818. But i also feel its a little silly to make a comparison with other cars when gearing (torque multiplication) has equal if not more effect on what you feel and what gets a car moving than the engine itself. (start a car in 4th or 5th gear then tell me that it has a torquey motor)

[Gollum]

I dare you then, to compare peak torque numbers from not very efficient motors, to very efficient motors. I'll even get the ball rolling for you.

2 Liter Honda S2000 - 153ft lbs = 76.5 pounds per liter

6.4 liter 1965 Pontiac GTO 389 - 431lbs = 67.3 pounds per liter

So gearing aside (though that's a valid topic, it's not what I was really going after in this thread) you can see that even the most efficient 2 liter will never be able to compete with just a 2.5 liter in regards to torque available off the line. Let's break that statement down.

Let's say that a peak production engine is around 77 pounds per liter.

2 Liters x 77 = 154

Now let's say there's actually any motor that still makes a measly 66 pounds per liter

2.5 Liters x 66 = 165

This is why displacement to weight REALLY DOES MATTER regarding how a car "feels". You simply can't get around the fact that a motor will only have so much displacement to work with off the line. Now, generally high efficiency motors generally have a higher RPM band for their power, making them good motors when the application suits them. But I've driven enough 13 second hondas and 13 second mustangs to know which "feels" more powerful. Which is more fun is a totally different discussion, but my point with this thread is that even at 2.5 liters, boost aside, the 818 is going to "feel" torquey.

And my point with this particular post, was to show that in most cases, adding just a few cubic inches can actually make MORE of a difference than a pew points of compression regarding off the line "feel". Tuned intake lengths, optimum cam profile, perfectly timed ignition events, and all of those other HP chasing tuning measures hardly make squat difference at how an engine feels when mulling around in 5th gear around town. Sure it makes a difference when racing, but now we're talking about a HP to weight ratio situation, not torque to weight, which is what I chose to make this thread about.

[Gollum]

Also, just to add a little bit to the above comparison. Let's assume you cruise around town at 2,500rpm in both engines listed above.

The 2 liter will have 73.3hp available "on tap" if you punch to WOT.

the 2.5 liter will have 78.5hp available "on tap" if you punch to WOT

Keep in mind that's like comparing an ancient 2.5 liter that's probably not even SOHC, and a 2 liter that's a modern DOHC. The comparison between a subaru 2 liter and 2.5 liter will be night and day off (and on) boost.

[StatGSR]

whats the CR on a 65 GTO engine? just curious, I don't know crap about old V8s.

My point about CR is that 8.2 (turbo subaru) is substantially different than 10.0 or higher especially at a lower rpm. its apparent in the low rpms when you compare a NA ej25 to a turbo ej25.

I also think using the peak torque number is a silly way of comparing. its always about the area under the curve (or at least points along the curve, not just one point), and your gearing is what lets you make the best use of that.

I'm just saying that the idea of "displacement to weight" is a little to vague to mean much of anything to me. A big engine with the wrong gearing can still suck regardless of the 1000lb weight difference. This just may be a better point if we discussed all major things involved in the appropriate way (area under the curve/weight/gearing). even if you assume gearing to be equal, you can have two 2.5s that behave extremely differently because of the engine design and compression ratio.

heck if you want to get crazy we could talk about what e85 tune does to the torque curve of a 2.5 wrx....

[Gollum]

Using peak torque numbers might not be a perfect apples to apples example, but most people see that in most dynos torque is much closer to peak at lower RPM than it is at higher RPM. Past peak torque most motors start to roll off considerably, and this is actually were we create what most know as "area under the curve". Motors who's torque does not fall off at all will end up with a very linear power band, also described as "peaky" to some, like the typical small displacement 4 cylinder.

Oh, and the difference between a 8.5:1 cr WRX motor and a 10:1 cr WRX motor will be more noticeable UP TOP, not down low. Why? Because the ratio in power difference is the same, thus the difference at high power gets larger, while at the bottom the difference will be harder to perceive. If a change in compression makes say, a 15hp difference, that will be a peak difference most likely at or near peak HP. It won't make a 15hp difference across the RPM band, and will most likely make much less than a 5hp difference at cruising RPMS. The difference will be a linear difference if all things are equal. Where most people get confused about the matter is that most motors designed for increased compression are rarely equal than lower compression counterparts. Usually there's a slightly different chamber design, along with completely different cam designs. A higher compression setup can use more camshaft timing all things being equal even.

And again, re-read my first post. I'm wanting to address the "feel" of a motor for those that have preconceived notions of 4 cylinders being "weak", which the generally are. I'm wanting to put things into perspective for people. And in the end, displacement is a huge factor of any engine, and should be a factor for anyone building a car. It's a huge building block that can't be ignored.

Oh, and I'm no expert on GTO's but I think the one I quoted was around 10:1-10.5:1. So if you dropped that motor down to 8.5:1 it could be as low as 65 pounds of torque per liter.

But since it's been brought up that a pure "displacement to weight" figure might be vague or inconclusive, let's just talk about torque to weight and where that torque shows up in the RPM band. Though I already have a good idea of where this will lead.


I'm just going to come up with some random cars off the top of my head and then go pull the figures for them.

'96 Miata
---Weight---------------2293lbs
---Displacement---------1.8L
---Peak Torque---------114
---Peak Torque RPM-----5,500
---Torque Per Liter------65.5
---Torque per Pound----20.11 Lower is better

'03 350Z
---Weight---------------3188lbs
---Displacement---------3.5L
---Peak Torque---------274
---Peak Torque RPM-----4,800
---Torque Per Liter------78.2
---Torque to weight----11.63 Lower is better
'01 Mustang GT
---Weight---------------3273lbs
---Displacement---------4.6L
---Peak Torque---------302
---Peak Torque RPM-----5250
---Torque Per Liter------65.6
---Torque to weight----10.83 Lower is better
'93 MR2 (non turbo)
---Weight---------------2599lbs
---Displacement---------2.2
---Peak Torque---------140
---Peak Torque RPM-----4400
---Torque Per Liter------63.63
---Torque to weight----18.56 Lower is better
'93' MR2 Turbo
---Weight---------------2758lbs
---Displacement---------2.0L
---Peak Torque---------200
---Peak Torque RPM-----3200
---Torque Per Liter------100 (see how easily even this mild turbocharged engine breaks the limits of even the extreme NA motors?)
---Torque to weight----13.79 Lower is better
'98 Lexus SC400
---Weight---------------3655lbs
---Displacement---------4.0L
---Peak Torque---------300
---Peak Torque RPM-----4000
---Torque Per Liter------75
---Torque to weight----12.18 Lower is better
'01 BMW M3
---Weight---------------3415lbs
---Displacement---------3.2L
---Peak Torque---------262
---Peak Torque RPM-----4900
---Torque Per Liter------81.87 (anyone who doesn't recognize this motor is a beast is blind!)
---Torque to weight----13.03 Lower is better
'04 Corvette
---Weight---------------3214lbs
---Displacement---------5.7L
---Peak Torque---------360
---Peak Torque RPM-----4000
---Torque Per Liter------63.15
---Torque to weight----8.92 Lower is better
'92 Mustang
---Weight---------------3010lbs
---Displacement---------5.0L
---Peak Torque---------300
---Peak Torque RPM-----3200
---Torque Per Liter------60
---Torque to weight----10.03 Lower is better
(I believe this car to be underrated by roughly 10% which would explain the absurdly low torque to displacement figure)


So by what I've said in this thread, and what I'm going on about, is that the vette will "feel" the fastest and have the most power available on demand wherever you end up, which is what most muscle guys perceive as "muscle". Unfortunately that's not the only factor on how fast a car actually is. The big surprise here is that though the vette is indeed the fastest above, the M3 is darn close, despite being rather middle of the field in torque. That being said though, the M3 doesn't feel exceptionally fast when you're sitting in it. Sure it feels quick, but it doesn't feel anything like a vette. This is because the M3 has a huge RPM band and simply doesn't have the power off idle that it has waiting for you up at the top of it's RPM band. This motor needs to be in it's sweet spot to sing, and rewards you for keeping it there with BMW's superb gearbox.

The hidden mystery here though, is that torque is an almost useless measurement. Without RPM you don't really feel any torque at all, and torque + RPM = POWER!!!!

It's really the off idle POWER that you feel in a big displacement engine. But idle in a 4 cylinder and idle in a huge V8 are roughly the same. So while one engine has torque on it's side right off the line, the other doesn't. That's why this topic is here. Because displacement DOES matter.

So looking at the 818
2.5 NA motor
---Weight---------------1800lbs
---Displacement---------2.5L
---Peak Torque---------166 (note that '01-'07 all share the same torque, though vary in power)
---Peak Torque RPM-----4400
---Torque Per Liter------66.4
---Torque to weight----10.84 Lower is better

2.0 Turbo
---Weight---------------1800lbs
---Displacement---------2.0L
---Peak Torque---------217
---Peak Torque RPM-----4000
---Torque Per Liter------108.5
---Torque to weight----8.29 Lower is better

2.5 Turbo
---Weight---------------1800lbs
---Displacement---------2.5L
---Peak Torque---------235
---Peak Torque RPM-----3600 (note the lower RPM, due to displacement creating sooner full boost)
---Torque Per Liter------94 (shows room for boost increase with stress being equal)
---Torque to weight----7.65 Lower is better

So though the 2.5 doesn't yield much in power stock for stock, I'd say that it's definitely the way to go if you're worry about having enough oomph from a little 4 cylinder.

Either way, any turbo variant, one boost is going, should feel like it's got more muscle than a 5.7 liter vette. Not bad for a little 4 banger eh? Even that split second before boost shows up it should feel comparable to a stock mustang GT. Not bad either.

Of course with tuning, and things like E85 everything changes. I haven't gone there in this thread (despite loving E85) because any of the above cars could be modified as well. Obviously when you're working with less weight every little change gets amplified, but I think my point stands that even a 818 in NA trim will still feel pretty darn torque-filled in the grand scheme of things.

[crackedcornish]

any idea where the h6 powerplants would fit in this torque to weight scale?

[Gollum]

No, because H6 motors are for lame people!

Oh come on, here ya go

3.0 Liter
---Weight---------------1800lbs
---Displacement---------3.0L
---Peak Torque---------219
---Peak Torque RPM-----4200
---Torque Per Liter------73
---Torque to weight----8.21 Lower is better
3.6 Liter
---Weight---------------1800lbs
---Displacement---------3.6L
---Peak Torque---------247
---Peak Torque RPM-----4400
---Torque Per Liter------68.6
---Torque to weight----7.28 Lower is better

Notice something kind funny (to me at least), that the peak torque on the H6 motors show up later despite having more displacement. This shows that even a 250hp turbocharged 2.0 liter versus the 256hp 3.6 H6 NA wouldn't be a contest. The turbo motor will spool quick enough to give that motor a nice fat power curve.

The only place the H6 will really help out is in having that "instant" response people like out of NA motors.

[StatGSR]

The 818, at 1800 pounds with the 2 liter engine is at 900 pounds per liter, and with the 2.5 is at 720 pounds per liter.

So you see, even WITHOUT boost, the 818 should feel as torquey as most of the modern muscle cars and even better than the lotus.




It's really the off idle POWER that you feel in a big displacement engine. But idle in a 4 cylinder and idle in a huge V8 are roughly the same. So while one engine has torque on it's side right off the line, the other doesn't. That's why this topic is here. Because displacement DOES matter.




The only place the H6 will really help out is in having that "instant" response people like out of NA motors.

Its Like you make the point for me then forget about it instantly.

Instant torque and a linear power band is what makes and engine feel "muscley". Obviously it can be noted that larger engines make more torque (that's because they are usually used to move larger things), i wont deny that there is certainly a relationship to displacement and torque, but to make any reasonable conclusion you have to compare apples to apples not apples to oranges.

When you start making constants, like NA vs turbo 2.5. the NA will still feel like it has more muscle because it has it has more instant low end torque because it has a higher compression ratio (obviously a turbo 2.5 with a similar CR will behave the same way, but still have a better top end than the NA engine). the turbo although having a higher peak torque and heck it still might have a higher peak torque sooner than the NA, will bog instantly until boost starts to build and the Dynamic CR for the engine goes up. (think of boost as a means to simulate a higher CR as you are able to compress more air that you would be otherwise). In a very simple explanation an engine designed for boost (lower CR to prevent detonation) that is not seeing any boost, is basically just a poorly designed NA engine.

The power bands of both are extremely different. but the average turbo vehicle is still going to be plagued with poor instant pre boost torque because it doesn't have the CR to make the torque under vacuum.

So I argue that the 818 with a stock block ej25 turbo will not feel as "torquey" as a modern mustang or similar, even with the weight being as low as it will be (the lower weight should actually reduce engine load, turbo engines rely on rpm and engine load to create boost). Yes it will get up and go pretty quickly when your ring it through the gears, but i though this thread was about the instant gratification similar to that of a muscle car.



So at 2.5 liters, you can expect around 180+ foot pounds of torque available off idle.
^ and that is just flat out wrong....



I think Brandon is on the same page as me... Peak torque even at a higher or lower rpm doesn't tell you about the entire power band for that engine.

[PhyrraM]

I'll ignore the charts and numbers. What I can say is that in the 'real' world the H6 *feels* better. And, to me, the feel is what this car is going to be all about.

Recently, my wife was shopping for a new car. She knew she wanted an SUV of some sort, but was unsure what kind or size. So we drove ALOT of cars. The '10 H6 Outback was BY FAR the most enjoyable off the line. Weight and Torque. For comparision we drove the Turbo Forester, the Mazda CX-9, Mazda CX-7 (turbo), the Ford Edge, the Chevy Equinox and the GMC Envoy - among others. All had good freeway power, but many were slow off-the-line. She chose the Mazda CX-9, mostly because of the way it looks.

Now, for me, comparing the Turbo Forester to the H6 Outback was interesting. Both weigh about the same, and are in similier packages. I WANTED to like the Forester better, and when it was pushed it was better and more fun. But when scaled back to the cruising level, where 85% of street driving is for me, the H6 was simply the obvious choice. And when the H6 Outback was pushed, it really lost very little to the turbo 4.

How that all applies to the 818? Not sure, but take it for what it's worth. In any case, mine will still be a turbo 4 - but I completely understand why an H6 should be on the table.

I'm guessing the FFR won't build so tight that the newer H6s won't fit. So unless you had your heart set on the old SVX 3.3, the point is likely moot.

[Gollum]

Re-reading that statement, that about torque off idle I agree that wasn't a correct statement. But to say that you'll have close to 180 pounds of torque available at WOT in most gears WOULD be accurate I think. I've also been talking crank numbers, as we've been seeing figures based on production ratings. The above dynos are at the wheels, and we all know about drivetrain losses. That last dyno isn't even breaking 180hp.

StatGSR - I still think you're completely wrong about compression, and to me you seem to have very little experience driving a variety of engines. I daily drive an engine that's a mere 8.4:1 compression ratio NA, and I can tell you exactly what power I'd gain if I ramped it all the way up to 10:1 compression. It isn't as big as you might think. The power loss off boost has other factors involved. Oh, and you're wrong about a muscle car's powerband. NON-Linear power is the staple of muscle car power. Most muscle cars' engines produce a peak HP curve that has at least 80% of peak power for more than a 3k RPM window, due to the severe torque roll off at higher RPM. This is usually because they're only producing a measly 80hp per liter or less. Though this means they're not very high HP per cubic inch motors, it makes them very powerful for their HP rating when comparing to a high strung motor of the same power levels.

I never meant to come across that the H6 was a bad idea. I think for those looking for a good all around street vehicle a H6 might be a great option. Or even as brandon pointed out, you're doing a lot of tight course auto-x. I personally feel that much of racing is finding yourself in the right gear at the right time, but hey, everyone has their opinions as to how to get the fast lap times.

But going back to turbo versus NA torque. I think the big confusion here is, as brandon pointed out, a turbo'ed engine doesn't produce near peak torque across it's RPM band. Quite the opposite actually. This is also why I made the comparison that "off boost it will feel similar to a mustang". Remember that the mustangs I put up only run compression rations around 9:1 anyways... But off boost a turbo'ed motor IS 95% the same as an NA engine of the same compression ratio, and compression ratios will make about another 5% difference. Let me see if I can pull up a NA falt 4 dyno here.

http://otakureviews.net/images/PeteDynoSheet.jpg

At 2600 RPM we'll say this engine is making about 118 pounds of torque. This is also a 2.5 RS motor, which means it's working with more displacement. Now referencing the above 2.0 turbo dyno brandon posted, it's making about 100 pounds at 2600 rpm...

...wow, that's pretty darn close to what I'd have estimated.... If this were a turbo'ed 2.5 I'd guess it'd be close to same as the NA dyno I posted.

Again, the "lack of torque" off boost in most turbo'ed vehicles is due to the fact that the displacement compared to the weight of the vehicle. You can't move a 2500 pound vehicle with less than 2 liters without boost and feel "torquey". I've also driven enough turbocharged muscle cars to know that they still retain loads of low end grunt off boost, and you'd never be able to tell if they did drop a few ponies at the bottom end off boost.

Jeremy clarkson in his review of the EVO on top gear, did a comparison showing that accelerating in 5th gear from a stop the EVO was just a dog. Some people watch that segment and say "wow, turbo cars sucks at low RPM" but that's a half-truth. The reality is that a non-turbo'ed lancer would do the same thing... When it comes down to it, it's a 3200+ pound vehicle with a 2 liter engine in it. There's no hope in hell to move that mass without getting the RPM's up.

By contrast, go drive a turbo diesel F350 truck. With no load on them, you can start in 3rd and then shift to 5th straight from there and they'll get up and MOVE. Even putting a 2,000 pound load in the bed hardly effects them. You might have to start in 2nd now... Boohoo. These trucks demonstrate how torque works. If you have enough of it at low RPM it doesn't take much to get things moving. Once you add enough weight, to raise the weight to torque ratio everything changes. It doesn't matter if you have 800 pounds of torque if you're trying to move 10,000 or more pounds.


In closing, as to why I personally don't want to H6, or even see much of a point, is that with a target weight of 1800 pounds I think it's low end torque is overkill for this application, and I feel they're too limited when it comes to raw HP numbers. The road for the 2.5 is well traveled and known. You can make quite impressive numbers with ease, and I think this is where the 818 will really shine. I can't lie though, the thought of bolting on a supercharger has crossed my mind...

[Wilky]

I was looking at the HP and TQ of the Lotus Elise N/a compared to the 2.5 N/A Subaru Engine and I think the Subbie engine be fine.
The Lotus/Toyota engine-Torque: 133 ft-lbs. @ 6800 rpm and Horsepower: 189 hp @ 7800 rpm
The Subaru engine- Torque: 166 ft-lbs. @ 4400 rpm and Horsepower: 173 hp @ 6000 rpm

[JRL]

Torque is a function of stroke. The bigger the stroke the more leverage on the crankshaft = more torque. You can have two engines of equal displacement with huge differences in torque based on the stroke of each. Compression ratio also has an effect on torque. If you have a long stroke you need higher compression to create maximum torque - think diesel.

[Gollum]

Actually that top gear episode with the evo in question was about the FQ400, a 400 hp evo, factory tuned with a giant Garret turbo. It bogged down in the road speed test I. 5th gear because the turbo was too big for the car.

Further, compression ratio is just one small portion of the torque output equation. There's volumetric efficientcy, intake mix (how well the heads mix the fuel/gas mix before combustion) friction loss, cross-chamber back-pressure etc etc that determines output of an engine per displacement.

The argument at hand is about how the 818 will feel when driven compared to other cars based on torque to weight. Regardless of the turbo lag etc, it's gonna feel good for a general duty grassroots motorsports car (no pun intended). If you wanted to get granular though, for someone dead-set on taking trophies home at autocross events, an n/a H6 will provide better results because of less shifting. On a road course, a turbo 4 will be better because you can get more peak power.

All in all, the 4 bangers will do but you have to be wary of turbo selection if you're wanting to be competitive in particular events. 2wd will make turbo torque surge and engine bog due to lag something to contend with. Gearing can address that but also limit top speed. Or you can be like me, get a turbo that's not too big and not too small for the engine, accept that overall 310 whp is about the max a EJ 4 banger will put out without serius sacrifice to drivability and reliability the adapt driving style. I'm a general purpose enthusiast though, I'm after overall balance between cost, reliability, performance and complexity. For those more serius about a single event, all these arguments are relevant and the right answer is subjective to the goals of the driver.

Fair enough?

All fair statements, though I don't personally feel the turbo in the FQ400 is all too big. It's just not for someone who doesn't understand the drawbacks.


I was looking at the HP and TQ of the Lotus Elise N/a compared to the 2.5 N/A Subaru Engine and I think the Subbie engine be fine.
The Lotus/Toyota engine-Torque: 133 ft-lbs. @ 6800 rpm and Horsepower: 189 hp @ 7800 rpm
The Subaru engine- Torque: 166 ft-lbs. @ 4400 rpm and Horsepower: 173 hp @ 6000 rpm

And this is part of why I brought this topic up. Even in NA trim, the displacement of these motors will allow the 818 to really kick some butt, even with "only" 170ish HP. Even a NA 818 should eat a lotus for lunch.


Torque is a function of stroke. The bigger the stroke the more leverage on the crankshaft = more torque. You can have two engines of equal displacement with huge differences in torque based on the stroke of each. Compression ratio also has an effect on torque. If you have a long stroke you need higher compression to create maximum torque - think diesel.

Torque isn't just a function of stroke. Otherwise you'd be able to calculate torque to stroke length and end up with a reasonable average that matches volumetric efficiency. This isn't the case though. Torque = Volume + Efficiencys - Friction Losses. A longer stroke engine tends to show it's power earlier on, but that's nothing to do with torque quantity. Lemme see if I can dig up some good examples.

Ahh, here we go.

Hayabusa bike engine has a 3.19 x 2.56 bore/stroke. It produces 102lbs of torque.

Honda B16 has a 3.19 x 3.05 bore/stroke. It produces 106lbs of torque.

Now, I know for a fact that while the hayabusa it's near it's limits and doesn't have much to gain, the B16 can get another 5-10lbs without too much work.

So the hayabusa has a torque/stroke ratio of 39.84 lbs of torque per inch of stroke.

The B16 has 34.75. Wow, that seems pretty low for a motor with so much stroke by comparison doesn't it? Let's just make is Torque/Volume and see what we get.

Busa - 78.46 lbs per liter
B16 - 66.25 lbs per liter

Personally those numbers tell me more and tell a better story. I can now conclude that the B16 isn't nearly as Volumetrically Efficient. If I base the torque just off of stroke, then nothing makes sense. Why on earth does the busa make so much torque having just 3/4 of the stroke? If that's the case then the difference in efficiency are on other planets. But if I take the entire displacement into account, their efficiency levels come into comparable arenas. Just because the B16 has more stroke doesn't mean it's going to produce more torque.

The reason people have believe what you believe JRL, is largely because of the american V8 scene. People stroke their motors and they get more torque, so people assume stroke = torque. This is far from the case. There's a lot more involved, and torque is ALWAYS directly related to volumetric efficiency. Just check out some engine simulation software to verify that yourself.

Also, a longer stroke motor doesn't "need" compression to make power. The reason most diesels are long stroke has to do with the fact they're engineered for lots of low RPM power, not top end speed. Diesel motors are inherently good at that anyways (especially before direct injection diesels came onto the scene). So they're just designing a motor that plays to the strengths of the fuel design and making a good combination. Look at 18 wheelers. You wouldn't wanta high revving engine in one of those because it'd just wear out faster. Low RPM grunt just plain makes sense. So you make the stroke large to get your displacement with more piston speed at lower RPM, thereby making "low RPM power" part of the design fundamentals.

Also, it should be noted that a large stroke engine has an EASIER time getting high compression. If you take a Ford 302, and stroke it to 331, then you will now have as much as 2 extra points of compression with the same piston to deck clearance and the same cylinder heads. Engines that are short bore high compression like bike engines, have to use extremely small combustion chambers to get the compression they're looking for.

If you want, later today I'll post some dyno graphs from dyno2003 of exactly what you suggested though. Two motors of the same size. One over square, one under square. We'll see what we get if volumetric efficiency is the same.

[BrandonDrums]

Torque isn't just a function of stroke. Otherwise you'd be able to calculate torque to stroke length and end up with a reasonable average that matches volumetric efficiency. This isn't the case though. Torque = Volume + Efficiencys - Friction Losses. A longer stroke engine tends to show it's power earlier on, but that's nothing to do with torque quantity.


Very well put. If torque just depended on stroke we'd all be mechanical engineers.

You're also right about the turbo on that FQ400, it's not "too big" so to speak, it just has it's application which is top-end numbers for that engine. The drawback being a giant loss of power down low. I was mainly pointing this information out to counter the statement made about the performance of that evo being the same down low as a regular n/a lancer. I'm pretty sure that turbo was stealing a good 80-100 ft-lbs of torque down low that the N/A version would have. A turbo engine doesn't become n/a off boost, the turbo steals power when it's not producing it.

[armstrom]

Keep in mind there is a fundamental difference between a 2.5L NA motor and a 2.5L turbo motor off boost. When the turbo isn't spooled up it is acting like a huge restriction in your exhaust (well, it always is, but that restriction is more than compensated for by the additional power once you get into positive boost). Also as others have said the low compression ratio really affects the VE of the engine when off boost. I would expect the 818 with a stock setup to spool slightly slower than if it were in the subaru body with AWD intact due to the decreased load on the engine. However, this will be balanced out by the decreased weight.. so we should still see neck-snapping acceleration no matter how you slice it. And if you want instant torque (and dont mind eating through turbos a little quickly) most EMS systems have anti-lag that will do a fine job at giving you full boost off the line :) Just don't use it in front of a cop, or near any windows you don't want broken :)

[JRL]

Never mind

[BrandonDrums]

Sorry JRL, I think my and all of our desires to know a lot and show off about it might have made us over zealous. You have a good point and the bravery to be brief about it.

[Gollum]

I'm pretty sure that turbo was stealing a good 80-100 ft-lbs of torque down low that the N/A version would have. A turbo engine doesn't become n/a off boost, the turbo steals power when it's not producing it.

I know you probably rushed these guesses, but really? The NA lancer only produces a whopping 146lbs of torque at peak, probably around 100-120 pounds off the line.

This is where that video is SO misleading. He's in TOP GEAR! Any 4 door sedan, even as light as the evo, with just a 2 liter motor is going to struggle like MAD from a stand still in it's top gear. I dare anyone here to video a similar situation in a NA vehicle and show us how it goes.

Yes the turbo robs some power, but it's not nearly as much as people seem to think. Much of how a turbo works is off of heat, not just airflow. If it WERE just an airflow device, it WOULD create massive amounts of restriction in the exhaust, thus killing power off boost. But that's not the case. Yes there's some pumping losses added from a turbo, but it really isn't much. One of the real beauties of a turbo is that it doesn't rob as much power as a supercharger, which are known to sap an amazing 5+hp on some of the larger production eatons. I think the large roots on top fuels need something like 20hp to run them. But that's if my memory serves correct, which it might not be. Turbos can essentially turn off, and instead present a dynamic restriction that's independent of the engine itself.

Remember, the engine is basically an air pump. The exhaust valve (for the most part) is closed when the intake valve opens. This makes the process of air entering and air exiting separate events in the engine. Adding a little bit of restriction in the exhaust cycle doesn't prevent air from entering on the intake cycle, which is where the real power is made. Most of the real power to be gained in exhaust systems is in frequency tuning to allow for scavenging to literally PULL air out of the chamber. This is usually strongest at certain RPM and headers are tuned accordingly. Most OEM NA setups don't come close to anything that complicated.

Instead what the turbo is causing is considered "pumping losses" since it's essentially making it take more energy to push the piston back up in the exhaust cycle. And remember that the larger turbo on the FQ400 is a larger exhaust turbine also with a higher AR. This means it's robbing LESS power at lower rpm because it's a freer flowing design.

I know it's a blanket statement. But I'd say that most turbo systems rob less power than having poor flowing OEM manifolds (if your turbo manifold is designed well that is). And I don't know about you guys, but I rarely see exhaust upgrades make more than a 2% torque difference. And usually that's all at the top, not at the bottom, which is why a free flowing exhaust will make more power. Down low, when RPMs are still low, there simply isn't the need for all the flow even most OEM manifolds offer. It's only once you get into the middle of the power range that it can become a restriction, and that's at the point where a turbo will spool almost instantly anyways...

I simply beg for some real world dyno comparisons. I'm going to go on the hunt myself but don't have much time tonight. My opinion still stands. A turbo engine off boost is still going to have 90% of the available torque of a NA counterpart of the same engine. And that the big reason a turbo engine feels "powerless" off boost is because it's usually a low displacement motor for the weight of the vehicle, and there's such a polar difference once the boost shows up.

[Gollum]

Ok, here's some dynos, all of which are of the VG30E motor, so though they will all vary from dyno to dyno, and engine to engine but they're at least apples to apples.

Here's a high HP monster
http://www.redz31.net/turbofaq/dynographs/jason84na2t6-8dyno.jpg

Notice that at 2000rpm it's making 180lbs of torque. That's 60 pounds per liter, which is impressive considering that's at the wheels and also well bellow the cam really coming "on". Also impressive considering the very low 7.8:1 compression

Another good HP motor
http://www.redz31.net/turbofaq/dynographs/BLOZUP.jpg

Notice how it's right in the same ballpark down at 2k. Also a 7.8:1 motor. Both these motors are using a T3/T4 though they're not identical.

Here's a mostly stock motor
http://www.redz31.net/turbofaq/dynographs/norcalzmandyno.jpg
It's actually making LESS power at 2k despite being 8.3:1 compression, and having a tiny T25 turbo that spools very quickly. Could be dyno differences, could be a lot of things. But it's enough of a difference to be interesting.

I'm doing all this to show something that I've been talking about all along. This motor even at the bottom of it's dyno is showing at least 60lbs of torque per liter (to the wheels). So my point is that the 818 with a 2.0 or 2.5 turbocharged motor will still have an AMAZING torque to weight ratio OFF BOOST that will pull like a mother, despite being "a tiny little 4 banger". I'm not saying people here have said that much, but I've seen enough people hinting with their lack of enthusiasm for the motor. I know it's tough to shake off the typical "big V8's are fun" attitude, and I'm all for it. But the point of this thread is that with the weight of the 818 you might be surprised just how hard this thing pulls around town in 5th gear.

[16g-95gsx]

This thread is bench racing at it's finest.

With a target weight of 1800lbs, the car has potential to be extremely quick. This entire thread can be summed up by just saying that. The rest of it falls into the "no ****" category, combined with over-the-top wordy bench racing.

The car has the specs that would make it fantastic in stock form and downright mind-blowing to someone with solid knowledge of building race cars.

[thebeerbaron]

This thread is bench racing at it's finest.

To be fair, there's not much to do between now, the day they announce the contest winners, and then the day the kits start arriving on doorsteps. I'm not sure what I'll do once the contest is over and I don't have a model to work on any more. Probably more silly threads like this (http://thefactoryfiveforum.com/showthread.php?1624-Is-it-FASTER-than-a-Yugo).

[Gollum]

Oh I know it's bench racing, and I'm not ashamed of it. Once I have an 818 in my hands I'll not be bothered with bench racing, and instead will be out proving things. But that's still some time aways.

[16g-95gsx]

As long as you guys realize what you're doing. I just see a lot of posting just for the sake of posting. I'm just as excited as the next guy, but I try to stay focused and am simply waiting until a final design actually comes out. The time that I've invested so far has been looking into Subaru specific info, as well as other vehicle platforms, as I personally am not sure that I'd run the Subaru setup still. Heck I even have an ECU company offer up sponsorship just last week when I showed them my interest in the project.

The car will be very fast. Anyone who has issues with running any sort of import engine, I don't really know what to say but perhaps "grow up". Racing is racing, and at this point in the game I'm sure that it has been proven that small displacement engines are more than capable of producing tremendous amounts of power when done correctly. My last car was 9 second 1/4m capable on the exact same street friendly trim that I would drive to work in on occasion, with nothing more than a 2.0L engine, full interior, sound system, etc. Combine that with a attractive, nimble, and lightweight chassis and I think you have a winner. I personally am used to extremely fast cars, so I don't plan to make mine anywhere near "stock", but to each his own and I'm sure no matter what you go with the car will be fantastic.

[BrandonDrums]

I know you probably rushed these guesses, but really? The NA lancer only produces a whopping 146lbs of torque at peak, probably around 100-120 pounds off the line.

This is where that video is SO misleading. He's in TOP GEAR! Any 4 door sedan, even as light as the evo, with just a 2 liter motor is going to struggle like MAD from a stand still in it's top gear. I dare anyone here to video a similar situation in a NA vehicle and show us how it goes.

Yes the turbo robs some power, but it's not nearly as much as people seem to think. Much of how a turbo works is off of heat, not just airflow. If it WERE just an airflow device, it WOULD create massive amounts of restriction in the exhaust, thus killing power off boost. But that's not the case. Yes there's some pumping losses added from a turbo, but it really isn't much. One of the real beauties of a turbo is that it doesn't rob as much power as a supercharger, which are known to sap an amazing 5+hp on some of the larger production eatons. I think the large roots on top fuels need something like 20hp to run them. But that's if my memory serves correct, which it might not be. Turbos can essentially turn off, and instead present a dynamic restriction that's independent of the engine itself.

Remember, the engine is basically an air pump. The exhaust valve (for the most part) is closed when the intake valve opens. This makes the process of air entering and air exiting separate events in the engine. Adding a little bit of restriction in the exhaust cycle doesn't prevent air from entering on the intake cycle, which is where the real power is made. Most of the real power to be gained in exhaust systems is in frequency tuning to allow for scavenging to literally PULL air out of the chamber. This is usually strongest at certain RPM and headers are tuned accordingly. Most OEM NA setups don't come close to anything that complicated.

Instead what the turbo is causing is considered "pumping losses" since it's essentially making it take more energy to push the piston back up in the exhaust cycle. And remember that the larger turbo on the FQ400 is a larger exhaust turbine also with a higher AR. This means it's robbing LESS power at lower rpm because it's a freer flowing design.

I know it's a blanket statement. But I'd say that most turbo systems rob less power than having poor flowing OEM manifolds (if your turbo manifold is designed well that is). And I don't know about you guys, but I rarely see exhaust upgrades make more than a 2% torque difference. And usually that's all at the top, not at the bottom, which is why a free flowing exhaust will make more power. Down low, when RPMs are still low, there simply isn't the need for all the flow even most OEM manifolds offer. It's only once you get into the middle of the power range that it can become a restriction, and that's at the point where a turbo will spool almost instantly anyways...

I simply beg for some real world dyno comparisons. I'm going to go on the hunt myself but don't have much time tonight. My opinion still stands. A turbo engine off boost is still going to have 90% of the available torque of a NA counterpart of the same engine. And that the big reason a turbo engine feels "powerless" off boost is because it's usually a low displacement motor for the weight of the vehicle, and there's such a polar difference once the boost shows up.


Not misleading, both cars were in top gear. The other car was a 1.6L Fiat. Let's end this thread.


http://www.youtube.com/watch?v=2cvFl7IQKe4

[readymix]

Not misleading, both cars were in top gear. The other car was a 1.6L Fiat. Let's end this thread.


http://www.youtube.com/watch?v=2cvFl7IQKe4

Asinine. Who puts their car in the top gear at 30mph and tries to accelerate? That isn't a real world test at all.

[Gollum]

I stand corrected, they both were in their top gear. But does anyone know the final gear ratios seen by both cars? I bet the fiat was a low range 5 speed designed for city use while the evo has a 6th gear designed for cruise... Fair comparison? Again, I bet a race between a lancer with the evo's gear box might have gone the same way...

[Kay95]

I am a subaru enthusiast for years now. There are allot of things you can do to improve spool.

You can get a external gate.
Switch the stock boost control solenoid for a 3 port type.
Open up the exhaust with a uppipe and ported header.
A simple retune.

You can make almost full boost before 2000rpms in some cases if you run a TD04 turbo with a external gate.


Check this forum out.
WWW.Nasioc.com

You can find allot of answers there.


I plan to get one of these kits. This is what I am going to do. Get a NA modern JDM 2.0 because they make 190HP stock. Swap the block out for a 2.5 and that should make atleast 220hp. That will have a broad torque band with plenty of power.

You can make 200hp on a older 2.5 with cams, exhaust and a tune. That would be fun and cheap.

[Gollum]

In doing some research on the Fiat Stilo in that top gear video, I'm come to the conclusion that what was scene is exactly as one should expect of the situation.

The evo is over 3200 pounds, AWD, and around 1250rpm. At that RPM it's probably got around a dismal 26 crank hp, putting wheel hp around 20-22hp.

The fiat is under 2800 pounds, FWD, and around 1330rpm. At that RPM it's probably got around 24 crank hp, putting wheel hp around 20-22hp.

Any displacement advantage of the EVO is easily offset by the added drivetrain loss with that slight RPM difference. Considering the lower weight of the Fiat, better drive ratio, smaller tires, less drivetrain to move, I think the video is very "real world". I strongly believe that even if you took the turbo off, and raised compression that the difference wouldn't have been a whole lot different at the start. I think the evo would haven't been pulled on quite so easily, but it still would have lost with ease.

Now, if they brought in a stock lancer that might be a different story. Shorter wheels, different gear ratios, less than half the drive train weight, lighter car, etc.

I think the point of Top Gear's video is to show that the more power you ask a turbo to put into a motor, the more contrast there becomes between on and off boost, and the harder it gets to keep it "on". This is a very real world point. I do NOT think their point it to show how much power a turbo "robs" down low which I think is a common internet myth not founded in real world principle or even race car engineering theory. The basic fact is that if you have a turbo that takes longer to spool it might "feel" like it robs power because you're operating close to a NA motor for longer until it kicks in. The contrast has become exaggerated.

But going back to that 450+whp 300ZX dyno I posted, he has huge amounts of power, and the contrast between lowest torque and peak torque is just insane. It must feel like something else when that turbo kicks in. But if you think about it, even that lowest torque figure is comparable to even at 2000rpms he has as much torque at the wheels as the NA motor has at peak. That's with a 7.8:1 compression versus a NA's 9:1 compression it's still dishing out loads of torque. And his top end work isn't that stellar. We're talking about home ported heads and a 100% home brewed attitude on his build. Even his turbo is a strange hybrid due to his budget mindset.

The point of this thread, and my point still, is that even a turbo'ed 818 will be anything but "mild" even off boost. Keep the turbo small and the power levels mild and the contrast won't be so insane, and it'll be one insanely fun car, even around town. Going "all out" might ruin it for some people, but obviously those people should know what they're getting into.

[readymix]

Down low, my turbo gage shows NEGATIVE boost pressure. That means there's a vacuum in my intake manifold. The engine isn't even getting atmospheric pressure which CERTAINLY means it's making less power than if the turbo wasn't there. I know this, I experience it EVERY DAY. An NA engine may see SOME negative boost pressure but that's only from the intake piping and air filter. A turbo engine STILL has intake piping and an air filter.

Uhhhhh. Guess how I know you have no idea how an internal combustion 4 cycle engine works?



The idea that a turbo operates on heat alone is also a myth. If all the turbo had to do was get hot, then after a hard drive it would be producing full spool just because it's at full operating temperature. "rising gasses" also mean squat unless you can funnel them into a system where they can generate pressure. PRESSURE and FLOW are the things that make heat a plus for turbochargers. The hotter the exhaust gasses are, the more energy per molecule the discharge has. So if the exhaust gas is very hot, it's expanding at a quicker rate thus escaping quicker and generating more pressure and because it's in a pipe seeking to get out it generates more velocity. However, hotter exhaust gases are also less dense which means the gas has less mass to exert forces on the turbine. This is where people start to think that turbos operate off of rising gases instead of air flow. On a car, higher EGT's do often translate to better spool but it's not really the heat that gives you the better spool but the added PRESSURE and VELOCITY that comes with heat that is responsible for the parity in turbo performance.

And what makes the pressure and the air flow, if not heat? And what...ahh, screw it. You start off by saying heat doesn't matter. Then you explain in detail why it does. Then there is something about gas density and molecules. Do you know why people wrap their exhaust header, crosspipe and uppipe? It isn't to keep engine bay temps down. It's to hold the thermal energy inside the pipes pre-turbo so that the heat maintains the exhaust pressure pre-turbo. Thermodynamics at work. Heat is energy, heat does work. And Aquamist isn't intended to cool the cycle, it's intended to up the effective flash point of the fuel, thus raising its effective resistance to pre-detonation. It's the poor man's race gas. It will cool the combustion chamber, the same as higher octane fuel will.



The turbine actually IS a turbine just like a Hydro-electric turbine works except the turbine on a turbo is attached to a compressor rather than a generator. The fluid in a hydro-turbine (water) is pushed around the turbine wheel via gravity thus generating the force on the fins of the turbine to rotate the system and produce mechanical movement that can be converted to electricity via a generator. Very little heat is required in this operation as you could imagine. A turbo would work the same way with cold air as it does with hot air and even water would work as well. Heat is only important for a turbocharger because of the system it's attached to: the internal combustion engine. When it comes to an internal combustion engine, it's difficult to generate cold-dense exhaust discharges because the power is coming from..combustion. It's easier to make better turbo spool on an internal combustion system by increasing exhaust gas velocity than it is to try to make the exhaust cold and dense obviously. However, things like Aquamist and Meth injection are available to calm, cool and improve the combustion process which also improves turbo spool by making the exhaust more dense and able to apply more force under low velocity than without it.

And how do we increase gas velocity? Hint, it has nothing to do with molecules. Well, not directly anyway.

And heat is important to THIS system because it isn't a hydroelectric generator. I don't understand your point in this comparison.


I wanted to leave this thread alone but please please stop telling people false information. I doubt it would be a problem but I'd hate for someone to buy the wrong turbo because they read your posts saying turbo lag is a myth. I really hope I have put this topic to rest. No offense man, I appreciate your enthusiasm but let's just let this topic alone for the time being. When you understand why a cycling engine produces vacuum, you can come on back and be condescending.

[Gollum]

How are my dyno's showing how much torque actually IS made, in the REAL world, OFF BOOST false information? Hmm... Seems like a hard one to refute in my mind.

You're the one (brandondrums) that made a huge blanket statement saying that evo "turbo was stealing a good 80-100 ft-lbs of torque down low"... I even tried to give you the benefit of the doubt that you were just throwing numbers out but you haven't come back to correct that obviously false statement. If that were the case then the Evo would be producing about 20-40 torque "down low" which frankly is impossible.

You're not the only one that drive a turbo every day. I understand that engines operate on vacuum under 90% of the time, even with a turbo (and even a supercharger in most cases). But open up that throttle, and I get to atmospheric in less than a second. That's some serious air restriction... I understand that with a NA it'd be instant, but even with a turbo the restriction isn't what you've made it out to be.

I never indented to communicate that turbo's work on heat alone. Such an idea would be mad. But as you've already explained heat does play a major role on the efficiency of a turbo. It's a double edge sword of course, but that's not really what this topic's about. What's interesting, and somewhat pertaining though, is that turbos "rob" more power when they're working hard than they do when they're not working much at all. When you're cruising down the freeway the turbo isn't doing much of any harm, causing less airflow restriction than most OEM filters (also remember the volume of air required to make the power to cruise is insubstantial compared to what the system is designed to be able to ingest), and when it's creating full boost, so much air is trying to get by the turbo you can actually have a higher PSI in your exhaust manifold than you do in your intake! Wowee!

But the power the turbo is robbing when working hard is easily given back in it's efficiency of design, which is largely based on thermodynamics. If you look at the energy required to get a STS system up to boost, and the turbine arrangement required, you'll see you could make a lot more power running a turbo up closer to the engine where it's hot, where the temperature differential is higher.

And another interesting point about the "power loss" of a turbo, is that the larger the turbo, the LESS it's theoretically "restricting" intake and exhaust gases, as the turbine is larger, allowing more airflow, and a larger compressor, allowing more airflow. Sure there means there's more mass with more inertia to get moving out of the way, but it's still a much larger hole for gases to work with. Or should I go dig up some more dyno's to show this? You can provide your own if you're like. It'd even be better if they have a MAP signal to go with it so we can see just how much power is really being made "or not made" before boost kicks in.

Again, the "power loss" often described isn't LOSS at all, it's torque differential. Torque off boost and on boost becomes increasingly high contrast, making the engine "feel" weak off boost. This usually isn't the case at all, as dyno's show.

[Gollum]

Just for grins :-D

Here's a stock NA supra dyno

http://carphotos.cardomain.com/ride_images/1/2739/4641/6847320087_large.jpg

Now let's look at a high HP turbo dyno...

http://i303.photobucket.com/albums/nn122/1BADMKIVTT/SupraDyno709SAE.jpg

First thing one should see is that it's obviously a turbo dyno, as you get that lovely boost onset torque that's concave, not convex. A supercharger, even centrifugal would be much more linear.

Now let's walk through it. Starting off you can see the system's response to sudden WOT movement at the bottom. The system "sets" in roughly 200-300rpm which on this dyno was probably less than the blink of an eye. By 3300 we have a true WOT figure, that looks to be around 160lbs of torque. The NA motor above was roughly the same... Now moving up, you can see the obvious hill climb of torque start right at 3500, so anything beyond that can be assumed to be under pressure, not vacuum. But what's interesting is that even before that point the torque closely resembled that of the NA counterpart. And more interesting, is that this isn't some mild engine. At over 700hp, assumings it's at the wheels is over 800hp at the crank. This is no slouch, and is most likely fairly low compression (bellow 9:1). The compressor needed to flow that much air is a big one, and the turbine attached to it won't be tiny either.

So even that huge turbo, doesn't seem to hurting much down low.... But if you've got over 600lbs of torque on tap when you hit the loud pedal at 6k rpm, the 140-160 lbs you have at the bottom before boost kicks in sure does feel "slow". That my friends, is the turbo "power loss" myth defined. It's a very real reality, but it's been attributed to all the wrong causes.

In the real world, I've never driven a turbo power car that I felt was more likely going to require a downshift to pass someone on the freeway/highway, than I do in a NA car.

[16g-95gsx]

Again, I have to say that this thread is retarded.

There are a thousand variables that go into the powerband of an engine. Just because one engine has a turbo and another does not does NOT imply a damn thing about how it breathes down low vs up top. Manifold tuning, cam tuning, engine timing, CR, hell even the damn fuel the car is running on will change it.

Do you really think that with a compressor wheel in the intake air stream that you have a vacuum on the post-compressor output? You do realize any vacuum that you're seeing is caused by the throttle plate, NOT the turbo. Go ahead and measure the pressure in your intercooler piping at idle, and you'll find that it's ALWAYS above ambient.

You guys are seriously putting way too much wasted thinking into this, and I'll be honest that from the perspective of someone who has worked on plenty of engines over my years it seems kinda lame. Again, I'm glad that people are hyped up on the car, and I'm hoping that it's just energy that you will ultimately focus on the car when you have a chance to, but I really think there is a lot more that could be done at this point in the game as far as research is concerned.

[Gollum]

Ummm, two of the three VG30ET dynos I posted start bellow 2k :confused:

People dyno testing a 600+hp supra start the dyno so high because they're not really working on tuning WOT down that low. They care about up top where it's going to explode. And I personally believe that if the dyno had started sooner, we wouldn't see torque so low at the start where it's just started recording.

Even going back to your dyno you posted brandon, the beginning of the dyno is super low, then ramps up. That's typical of any dyno that recorded right AT WOT, instead just just after.

And me, I DO drive my turbo'ed 2.8L inline 6 around town bellow 2k. Has a redline set at 7k and I shift around 2200-2500 when I'm cruising, dropping the revs down to 1800-2000. As long as I'm just accelerating with the normal rate of traffic (not trying to accelerate hard) then it's fine. My heavier 2.8L 280ZX that's NA will do the same, but is slightly more likely to bog down at low RPM because the car is about 300 pounds heavier.

[BrandonDrums]

Again, I have to say that this thread is retarded.

There are a thousand variables that go into the powerband of an engine. Just because one engine has a turbo and another does not does NOT imply a damn thing about how it breathes down low vs up top. Manifold tuning, cam tuning, engine timing, CR, hell even the damn fuel the car is running on will change it.

Do you really think that with a compressor wheel in the intake air stream that you have a vacuum on the post-compressor output? You do realize any vacuum that you're seeing is caused by the throttle plate, NOT the turbo. Go ahead and measure the pressure in your intercooler piping at idle, and you'll find that it's ALWAYS above ambient.

You guys are seriously putting way too much wasted thinking into this, and I'll be honest that from the perspective of someone who has worked on plenty of engines over my years it seems kinda lame. Again, I'm glad that people are hyped up on the car, and I'm hoping that it's just energy that you will ultimately focus on the car when you have a chance to, but I really think there is a lot more that could be done at this point in the game as far as research is concerned.

I feel the same way actually.

Oh wait, the Subaru boost gauge actually reads from the blow-off recycler which bolts on to the intercooler. If you see negative pressure on the boost gauge, it's actually being read directly from the intercooler itself which is before the throttle plate. That being said, I went ahead and measured my intercooler pressure at idle every day for the last 6 years. I'll let you know what I find.

Vaccum at idle and below ~2300 when my turbo isn't spooled.

Thank you.

[Wayne Presley]

My turbo car makes 5 lbs of boost at 1500 rpm. :D 22 psi at 6500 rpm

[Fast818]

For speed it is power to weight ratio but for performance/track cornering it suspension and setup (wheels,tires,shocks/coils,camber,castor and weight bias etc)

I would like 400-500 HP 2.5lt turbo motor 2000lb for the car, little comforts air con etc so P/W ratio and performance will be Fuunnn...!! :--)) should be good all round driving car

[StatGSR]

For speed it is power to weight ratio but for performance/track cornering it suspension and setup (wheels,tires,shocks/coils,camber,castor and weight bias etc)


Actually speed (read top speed) has more to do with Power and Aerodynamics, while all around performance has more to do with the weight of a car.

Aero has way more to do with a car going beyond 200mph certainly much more than the difference between lugging around an extra 1000lbs... take a look at the Veyron which weights in at about 4500 lbs dry... but that will do over 250mph... an ariel atom which maybe have the same or better power to weight would never be able to see that because it doesn't have the aerodynamic abilities...

[Fast818]

StatGSR Yes you are total correct. I am assuming the 818 will be Aerodynamic (go Dave and team..!!)
I think you might like this read on this link below. engine small mods (turbo,Injectors and mapping) on 2007 WRX STI for 438 HP

Cheers

http://bbs.scoobynet.com/projects-40/846290-starting-again-with-a-hawkeye.html

[kach22i]

something you guys might find interesting
http://www.060calculator.com/

Nice find, thanks.

Looks like if I can get 50 lbs off my car (not hard to do), I'll be a second quicker in the 0-60. Bet it stops quicker too. And I'll be able to keep up with the latest SUV's.

I need to finish the A/C delete, still have some hoses and blowers in her. Get the old heat exchangers, thermal reactor (1977 911) and stock muffler off. Maybe I'll slim down on the tools I travel with, already took out the spare tire.

Torque.................great for burn outs, not much use on a velocity or momentum racer. On an 911 the Torque may get you some wheel hop (not really a good thing), to be honest I don't know how a mid-engine car feels in a burn out 0-60 type thing. I've been a passenger in my buddies 1981 GT 308 Ferrari, and he drives harder than I do, at least in light traffic. Seems to lay down the power it has just fine.

[Steve91T]

Nice find, thanks.

Looks like if I can get 50 lbs off my car (not hard to do), I'll be a second quicker in the 0-60. Bet it stops quicker too. And I'll be able to keep up with the latest SUV's.

I need to finish the A/C delete, still have some hoses and blowers in her. Get the old heat exchangers, thermal reactor (1977 911) and stock muffler off. Maybe I'll slim down on the tools I travel with, already took out the spare tire.

Torque.................great for burn outs, not much use on a velocity or momentum racer. On an 911 the Torque may get you some wheel hop (not really a good thing), to be honest I don't know how a mid-engine car feels in a burn out 0-60 type thing. I've been a passenger in my buddies 1981 GT 308 Ferrari, and he drives harder than I do, at least in light traffic. Seems to lay down the power it has just fine.

I didn't look at the calculator, but are you saying that if you drop only 50 lbs, you'll be 1 second faster in 0-60? If you are, that's completely wrong. You'd have to drop way more than that. Many hundreds of lbs. Think about the difference in performance if you have a passenger or not. That's a lot of weight, doesn't really make that much of a difference.

Torque is very important. While it admit, it makes the car "feel" faster, it also makes the car much more drivable. Also it'll allow you to be faster on the track, allowing you to use the next higher gear, and shift less. Every time you shift, you loose time. I believe every shift adds .3 to your time. Doesn't sounds like much, but think of how much you are shifting. Just 3 or 4 less shifts around a track and you just gained 1 second.

I had a 310 hp MR2. It really puts the power down. I don't understand your comment about wheel hop. Is it a design of the 911? Or do you think because the 911 is rear engine, it gets wheel hop?

Mid/rear engine cars have amazing traction in every aspect. You have obviously more traction straight line, more traction coming out of a turn, and more traction under braking.

Steve

Thinking back on the 50 lbs comment. I'm thinking you must have meant .1 second. A tenth of a second I could see.

[kach22i]

I didn't look at the calculator, but are you saying that if you drop only 50 lbs, you'll be 1 second faster in 0-60? If you are, that's completely wrong.
I just figured that out, thanks.

No more posts when waking up at 5:00 in the morning with no breakfast and coffee.

It's more like .1 second not 1 full second - oops.

I'd have to take off something like 700 lbs for a one second drop in 0-60 times.


I had a 310 hp MR2. It really puts the power down. I don't understand your comment about wheel hop. Is it a design of the 911? Or do you think because the 911 is rear engine, it gets wheel hop?

You would have to drive a 911 to really understand what I mean. They are not designed for hole shots to say the least. The "hop" I speak of is very hard to duplicate. I've only done it once or twice myself. The first time was by accident after doing a full tune-up and valve adjustment, I just let the clutch out too quickly, the new added/extra power took me by surprise and I got a little hop. The Porsche forums talk about it sometimes, and the high powered 911's like the turbo are AWD for a reason I assume.

[Gollum]

Actually speed (read top speed) has more to do with Power and Aerodynamics, while all around performance has more to do with the weight of a car.

Aero has way more to do with a car going beyond 200mph certainly much more than the difference between lugging around an extra 1000lbs... take a look at the Veyron which weights in at about 4500 lbs dry... but that will do over 250mph... an ariel atom which maybe have the same or better power to weight would never be able to see that because it doesn't have the aerodynamic abilities...

It's actually interesting to look into the setups of the cars breaking records at bonneville. They're actually REALLY HEAVY! There's a record holding datsun 240z that comes in over 4000 pounds! Whoa! This might seem backwards, but top speed (as noted here just now) is about Aero and Power. The resistance of air at these 200+mph speeds is much more the issue than the weight you're pushing through that resistance. Every little part of the car will make a difference and teams spend years usually in the refining process to get a car as aerodynamic as their class rules will allow (or spend a lifetime on it depending on how you look at it).

I only post this to show that though lightweight = awesome performance doesn't mean it will "fit your needs". We all have and use our cars for different things and a marvelous car is one that does it's desired intent better than anything else could. As much as it pains me to say it, that's the beauty of the VW bug. It was cheap, reliable, and got the job done better than nearly any other car in it's competition range.

Personally though, first weekend I own a car I stripe the thing of almost all of it's interior. But that's just me. :-D