CR help??
CR help?? Im planning on running sts w/ an electronic boost controller, 5psi (for regualr street driving) and 15psi (for racing)...with AFR mongoose heads (72cc combustion chambers) and 346ci displacement should i run 8.5:1 or 10:1 compression. the car is going to be a street legal road race/autoX platform so fule miliage is a concern and i'm also planning to run zex direct port nitrous. obviously tuning is very important in a setup like this, but do you think, with a small tuning miracle, i could get away with 10:1 under 15psi and not blow the engine straight to the moon with a 100 shot of gas???
Well, if you strap a set of 72cc chamber heads on a stock LS1, you'll have about 9.4-.5 CR. 10:1 CR and 15 psi is not going to happen unless you limit the boost it makes untill 5500ish rpm, 15psi and low rpm = way too high cylinder pressure, throw nitrous into the mix and thats deadly.
Ryan K.
Ryan K.
9 Second Club
Joined: Nov 2003
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From: Norn Iron
Originally Posted by SS101
Im planning on running sts w/ an electronic boost controller, 5psi (for regualr street driving) and 15psi (for racing)...with AFR mongoose heads (72cc combustion chambers) and 346ci displacement should i run 8.5:1 or 10:1 compression. the car is going to be a street legal road race/autoX platform so fule miliage is a concern and i'm also planning to run zex direct port nitrous. obviously tuning is very important in a setup like this, but do you think, with a small tuning miracle, i could get away with 10:1 under 15psi and not blow the engine straight to the moon with a 100 shot of gas???
Why such extremes ? Why not somewhere in between ?
Im on 8.7:1 blowing via a Vortech, and can quite safely make 19psi at 7000rpm on pump fuel only.
why such extremes? well, i want to have something that no one else has...plus giving those expensive exotics a run for their money on the road course is something to look forward to as well. why 15psi? when you factor in the pressure loss from the the boost piping and the intercooler 15psi at the turbo outlet should equal about 12-14psi at the throttle body...why is that important? because 14.5psi ~ 1 bar and if you doulbe the bars of air going into your engine (1 bar is atmospheric pressure at sea level; ergo, all engines, at sea level, operate at at least 1 bar), you double the fuel and thus, double the power (in an ideal physical world). i'm aiming for 800rwhp (before the nitrous) and about 400-450rwhp on motor.
how will running at a lower compression ratio affect my fuel consuption and drivability at 5psi of boost (what i'll be running on the street)?
how will running at a lower compression ratio affect my fuel consuption and drivability at 5psi of boost (what i'll be running on the street)?
