Apologies for this being yet another "what turbo?" thread at its heart.

It's been a while since I've been following S2000 development; when I got out of it the UR kit was just coming to be, and there were only a couple guys doing any real pioneer work. The community has come a long way in the last couple years, and what was unknown then is trivially easy now.

Anyway, my question is what compression ratio and turbo do you guys think would be the right choice for the following setup with the following requirements:
Proposed setup:
2 liter F20C with built bottom end - sleeved, rods, pistons, etc.
Upgraded springs and retainers
AEM EMS, proper injectors
Full-Race exhaust manifold
Full-race/Hypertune intake mani if available
Custom liquid/air intercooler, with ice water reservoir
C116 or other suitable race gas, no methanol or alcohol (or NOS) injection allowed

Goals:
Broad torque curve coming in early - would like 250 ft-lbs. by 4500rpm, maintaining that torque level as long as possible. Rev limit would be raised to 9500, torque must not start falling off until at least 8500. A torque level above 280 for a large part of the 4500-8500 span would be good. Still, I'd give up peak torque to get more torque earlier in the powerband.

Car would be used for racing only and in 3-4 short bursts, 30-60 seconds at a time, not always at full throttle (autocross). This is why I thought the liquid/air would be preferred, in that it can get the charge air below ambient, and requires less volume, which should theoretically aid in faster spool.

I've read through about 20 pages of threads here to try and get caught up, and so far it doesn't look like anyone has built quite what I'm planning, yet. fperra's GT35 build is pretty close; the 330+ ft-lbs. it makes is actually a bit too much power for my needs; a setup like that with 40-50-fewer peak ft-lbs. but 500-1000rpm sooner spool would be pretty much ideal.

I'm not sure which A/R GT35 he used, and if perhaps a smaller one might meet those needs. The next step down from that looks like the GT3076, but I haven't seen anyone really go all out with one yet.

So, can it be done? Is the 3076 a better choice? Better to go with a lower CR and aim for more boost, or keep it a bit higher to help with the spool?

Ehhh, it's all hypothesis and conjecture at this point, please nobody spend too much time replying to silly old me.

 

Sounds like someone is trying to build an SM2 car?

 

For a project like this, there is a lot of work to be done on paper before the first part (or even the car itself) is bought.

 

The GT3076 would let you attain that and pretty much all of your goals can be met without much of an issue. I think your focus should be set more towards weight savings since your power requirements and spool up timing are fairly simple.

The air/water ic would be fairly heavy. I would suggest going with a v-mount setup because it would minimize overall piping which would have a greater effect on spool time than a mere 20 degrees. The only problem with an air/air is that in auto-x you aren't moving very fast but it can still work especially with a fan.

Compression ratio-wise, 10:1 and only 116 octane. Responsive engine would be what you are looking for.

 

Here are some dynos from my GT3076R with a 0.82 a/r turbine housing and custom tubular manifold. These are on 91 octane pump gas. The engine is built with 9.5:1 compression. Boost peaked at 16 psi and dropped to 10 by redline (which is why torque falls off). The boost drops on purpose because I only had enough injector for 10 psi at redline. The GT3071R would probably also meet your goals.

The top two are from a Superflow dyno. The bottom dyno is from a Dynojet. It shows two different curves (two different gears).




Tim

 

FYI- A-Spec offers a bottom mount, tubular, equal length manifold with a custom V-mount radiator/intercooler setup. They were also the first company to make a production S2000 kit with a GT series turbo. I'm not sure what turbo they're using, but it was a custom spec'd unit designed to provide very quick spool with good top end- I'll guess it's some vairant of the GT30R.

http://www.a-spectuning.com



Tim

 

Thanks for the info Tim, I hadn't run across your build in my research, looks like it'd be a blast to drive.

I will be very interested to see how the top half of your curve looks once the larger injectors are sourced. Your 2.2 at redline should be flowing approximately the same amount of air as a 2.0 at redline; if the .82 3076 can tolerate your application without wheezing, it should be able to work for me.

It looks like you have a 2.2, which means your boost will be coming in a bit sooner than mine would, though if I go 10:1 CR that would help make some of it back.

Are you using the a-spectuning v-mount setup? It looks very interesting.

Man, if anything, you guys are making too much power.. I'll look into some of the 3071R builds to see if they might work also... Thanks again!

 

You're welcome.

I've actually gone back to the 0.63 a/r I had since the dyno and have some 1000cc injectors with a FJO injector driver box waiting to go on. I'm hoping to retune for both faster spool and more top end! I'll post once I redyno, though it will probably be a while.

My setup is 100% custom. A-Spec hadn't released their kit (nor had Lovefab or most of the others) when I did my first setup with a log manifold. For the revision of it with the tubular top mount, nobody had anything that did exactly what I wanted so I went custom again.

Good luck!

Tim