When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
A single rear mount turbo with a large divided exhaust housing, quick spooling .5-.7 ar, and a relatively small compressor housing should do just fine with some small diameter heat wrapped pipes from the headers to the turbo.
The turbo charge pipe goes straight up through the trunk floor into a properly sized a2w intercooler, and can be routed through the cab or under the car to the throttle body. Have one hx in the trunk, getting air from naca ducts, and exhausting said air out the back of the car via an always on puller fan and screened vent cut in the back between the taillights. Run another hx up front as mentioned above.
Lots of corvette guys racing with rear mount turbo setups and being competitive, so see what they are using.
And it's still a turbo application, it's different, and fun, and challenging. Better weight distribution. The added length of the charge pipe helps with lowering iat's. The added length of oil plumbing also helps the oil cool down after exiting the turbo as it gets pumped forward to the engine.
I don't think the OP is looking for "... it won't be that difficult to...", as he specifically stated that he wants a fabrication challenge for this car.
I, personally, don't think a turbo, front or rear, is correct for time attack racing. A centrifugal blower or very well sorted out top mount blower is what I would prefer. But dude wants to use a turbo, so I'm catering my response to that.
I think it's perfectly possible for him to reach his modest goals and achieve decent spool time with a properly designed rear mount turbo. And, the added benefit of better weight distribution will make the car handle better (assuming he adjusts the suspension, blah blah blah). A car that handles better is more likely to be faster and win.
If he can overcome the challenges associated with spooling a rear mount turbo in a timely manner, then why not reap the benefits of better weight distribution in the process?
It doesn't take a big laggy turbo to push 600hp to the ground, so getting it to spool really shouldn't be a problem, even mounted in the rear.
How many turbocharged vehicles have you built? How many rear mounts? Did you actually plot out compressor maps to size the turbo properly or just picked a standard t76 cause everybody else does? The minimal weight gain of a properly setup front mount far outweighs any "benefit" of better weight distribution of a rear mount. Piping is substantially shorter, as is oiling and cooling needs depending on the turbo type, An FMIC and aluminum cold side weight is minimal and it can spool substantially faster and is more efficient at making power. I haven't even touched on boost thresholds at corner exit or what if it was a twin front mount.
Originally Posted by DavidBoren
I, personally, don't think a turbo, front or rear, is correct for time attack racing. A centrifugal blower or very well sorted out top mount blower is what I would prefer. But dude wants to use a turbo, so I'm catering my response to that.
I think it's perfectly possible for him to reach his modest goals and achieve decent spool time with a properly designed rear mount turbo. And, the added benefit of better weight distribution will make the car handle better (assuming he adjusts the suspension, blah blah blah). A car that handles better is more likely to be faster and win.
If he can overcome the challenges associated with spooling a rear mount turbo in a timely manner, then why not reap the benefits of better weight distribution in the process?
It doesn't take a big laggy turbo to push 600hp to the ground, so getting it to spool really shouldn't be a problem, even mounted in the rear.
Weight is irrelevant, and from a point of view front-rear a nonsense argument.
the difference relative to the car is negligible...it's not like this is F1 we're talking about.
There are just no sensible arguments in favour of a rear mount for such an application.
That isnt to say one cant be built and used for that application, but if going to all that trouble, may as well just build a system to achieve the best possible outcome, than building one with poor design from the outset.
Ok, OP don't take this the wrong way, but do you really need the extra power? There are PLENTY, of very fast corvettes out these with stock ish engines. Have you done all you can for the brakes, weight loss, suspension setup, aero and most importantly driver training, you can?
I apprisate that power is easy to increase with an LS engine. But there isn't always direct link to reduced lap times.
I would avoid turbo for your goals. I vote for big displacement, high compression. Less heat soak issues on multiple fronts and weight distribution will be better NA. I would put the money and efforts towards suspension, chassis, brakes, and MORE SEAT time. I have seen a lot of underbuilt cars destroy over built cars with the driver mod. Not saying your not good...but you can always get better.
At the most, I would consider a low boost centrifugal setup...Your typically always in higher RPM, so the loss of response compared to a roots or screw blower is not as significant and a centrifugal is more efficient and will make less heat assuming both are properly sized. However, the reliability of a centrifugal in a scenario such as yours would have me worried. I always hear of rebuilds occurring after only 10-20k miles of street use...
You're going to have problems with low mount turbos on an RX8. The frame rails are especially narrow. Even rotary guys have to make goofy forward-mounting turbo manifolds to fit older turbo rotaries in those cars. They also have a pretty small frontal area compared to a lot of other cars, so you'll have a challenge with stacked heat exchangers you'd need with a forced induction setup.
If you're married to the idea of turbos and want THE best response, the Borg Warner EFRs are king. Used Indycar EFR6758s (54mm comp) and EFR7163s (57mm comppop up on eBay occationally and can be had for ~$600 each. They're about the size of a GTX2867R and GTX3071R, but only weight 11lb each and will blow the Garretts away in regards to response. They're also pretty potent at about 53/60 lb/min EACH.
Here's a picture my twin EFR 6758 setup in a 2nd gen RX7/alum 5.3L below. Car isn't running yet, but I had the largest EFR 9180 (68mm) with the 13B and it would make 20psi by 3500 and rev to 8500, on a little rotary.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
