Forced Induction Question - anybody???
Thread Starter
Teching In
Joined: Nov 2001
Posts: 9
Likes: 0
From: Houston
Forced Induction Question - anybody??? Which is preferred with all other things being as equal as possible:
My car, as shown in data below, which has 10.5:1 CR and runs ~5-6 psi boost OR
my car with 9 - 9.5:1 CR running ~8 psi boost w/ smaller S/C pulley?
Question:
1.Which is the better setup if the hp/tq happen to be almost equal?
2.What are the pros and cons of each setup?
'02 C5 A4 Torch Red Coupe ---Powered by MTI---
3.42, Magnacharger S/C, Donaldson B'wing, MTI B-1 cam w/ Stg. II heads and TPIS headers, B&M Cooler and TransGo HD Pro shift kit, Precision 2800 TC, Deep Sump Tranny Pan, LS-1 Edit, Corsa Touring cat-back, Nitto 555's
Best track time: 11.87@119.4mph w/runflats
Top Speed: 175 mph @ 1/4 throttle
465rwhp/412rwtq - w/ Magnacharger (MTI)
386rwhp/360rwtq - before Magnacharger (MTI H/C)
(Stock 294/314)
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My car, as shown in data below, which has 10.5:1 CR and runs ~5-6 psi boost OR
my car with 9 - 9.5:1 CR running ~8 psi boost w/ smaller S/C pulley?
Question:
1.Which is the better setup if the hp/tq happen to be almost equal?
2.What are the pros and cons of each setup?
'02 C5 A4 Torch Red Coupe ---Powered by MTI---
3.42, Magnacharger S/C, Donaldson B'wing, MTI B-1 cam w/ Stg. II heads and TPIS headers, B&M Cooler and TransGo HD Pro shift kit, Precision 2800 TC, Deep Sump Tranny Pan, LS-1 Edit, Corsa Touring cat-back, Nitto 555's
Best track time: 11.87@119.4mph w/runflats
Top Speed: 175 mph @ 1/4 throttle
465rwhp/412rwtq - w/ Magnacharger (MTI)
386rwhp/360rwtq - before Magnacharger (MTI H/C)
(Stock 294/314)
--------------------
Re: Forced Induction Question - anybody??? well if HP/tq were equal for the different CR the lower would be better, becasue it has more margin for error for blowing your engine, deffinatly safer.
now the lower CR with more boost will make more power, no doubt about that, so that would be your pro's and con's
now the lower CR with more boost will make more power, no doubt about that, so that would be your pro's and con's
TECH Enthusiast
Joined: Dec 2001
Posts: 553
Likes: 0
From: Columbia, MD
Re: Forced Induction Question - anybody??? Lower your compression ratio and change to a smaller supercharger pulley. Remember, with the smaller pulley, the boost will come in quicker in the RPM range, which will compensate for a slight loss of N/A motor power in the low end. You can also change your rear-gears up to 3.73's to spin up even quicker to over compensate.
I went with 9.1:1 CR, a camshaft with max power at 6500RPM, 2.85" (11PSI) supercharger pulley, and 4.10 rear-end gears. I think that should put me right around 550RHWP/500RWTQ @ 6400RPMs, and a mid 10-sec run with 10PSI on pump gas and full car weight.
I went with 9.1:1 CR, a camshaft with max power at 6500RPM, 2.85" (11PSI) supercharger pulley, and 4.10 rear-end gears. I think that should put me right around 550RHWP/500RWTQ @ 6400RPMs, and a mid 10-sec run with 10PSI on pump gas and full car weight.
