Not necessarily. The turbo and intercooler efficiency will be less at 12psi and the tan at 7psi. So the horsepower relationship between the 7psi and 12 psi is not linear. You are not going to run a 5.0L 928 in the low 11s or high 10s with only 12 psi. Most of the boosted 5.0L V8s needs somewhere between 15-20 psi to reach that goal.

 

I'm know for sure traction will be an issue @ 12psi . but from a roll at 12psi he would hang or past some low 11' second cars.

 

it takes about 430rwhp/tq in a boosted Vet with wide tires to break an 11 with some practice. From what I've seen, about 550rwhp/tq minimum with some serious rubber/practice is needed to break a 10. 12psi by my calculations is about 500rwhp/tq on my system. An 11 second car for sure, but short of a 10 second pass (not considering clutch, tires, etc)

 

Mark,
Are you running an open diff. or an LSD unit on that car?

 

open diff.

I wish I had LSD

 

The new, completely stock C6 Z06 is putting down 450 rwhp, and clicking off 11.7's with ordinary drivers. The car weighs 3100 lbs, 400 lbs less than the portly S4, so the S4 will need an additional 40 rwhp just to overcome the weight difference. Let's just say then the S4 will need approximately 500 rwhp to hit 11.7.

It'll need approximately 600 rwhp to do 10.7.

 

They are probably supercharged.

Superchargers are vastly more innefficient than turbos at high boost levels. Compared to a SC at 12psi a well designed turbo system at the same boost level(and FAR more importantly- the same FLOW LEVEL) will probably make as much as 20% more peak power. A 12psi belt driven SC at 6k rpm is probably gobbling up around 100-125hp on a 5.0 liter engine at 6k rpms. An efficient turbo system at the same boost level probably consumes less than 10% of that amount.

 

An S4 would need approx 30 extra SAE hp(ie 530 SAE hp) to match a ZO6's power to weight ratio.

Running drag radials or slicks and running suitable tire pressures would greatly reduce the power required to turn an 11.0et with eiter(or any) car. Running an 11 flat in any 928 with street tires, almost regardless of power level, is probably a fantasy. It would take extensive chassis/suspension modification or an overwhelming amount of HP to get down there from way up here in a Shark...

 

Zo6's have short gears and 325mm rear tires too (& LSD) & lots of low end torque that's easily modulated by the pedal. Then again, it's a 70k Chevy (pass).

If I can spend 6k on a turbosystem & 4k on wheels & tires that gets me close to a Z06's performance, I'm happy.

 

Mark,

hope to see your video shared here soon.
That Supra took of like a rocket, amasing speed.

/Peter

 

Bill is editing it as we speak, should be "up" tomorrow. I have some stills from the vid, but in .Quicktime files, not Jpgs.

 

Here you go. Mark, I will be annotating with text later.

http://www.billsworkshop.com/P928S4/...12-9at114+.mov

EDIT: OK, the file corruption is fixed. WARNING - It's about 9MB.

 

Way to go Mark That Boost Logic Car is AMAZING

 

Mark, is this turbo kit workable with the 4.5 16v motor? me and my nephue have an 81 we are redoing, I know that Porsche built a factory 928 turbo for one of the "Porsche" family members but i cant remember if it was a 32 or 16v. also we have an auto, will it work?

 

Mark - it sounds like a beast. I cant wait to see more of the video.