Question for the FI guys
Question for the FI guys i just have a quick question for all you FI guys. i was bored at work the other day and was looking at super cars on the internet and i brought up the Saleen S7. i knew it was a twin turbo v8, but i didnt know it was an 11:1 compression motor. why does everyone usually lower the compression for a FI application? why did Saleen go with high compression for this TT setup? thanks
If you lower the compression the motor is much more maintenance friendly. you can run higher conpression with a SC/ Turbo but there is a lot more prep work to do. meaning studs instead of bolts, stonger pistons & connecting rods, head gastets ECT.
It is much easier to lower the compression and run higher boost than run higher compression. also you can run pump gas on the lower compression motor.
I just built an LS2 @ 9.0:1 with 10 PSI SC, and pulled 535 WRHP before I ran out of fuel. just have to upgrade thefuel pump and should be able to go over 550 WRHP.
Hope this helped
Al
It is much easier to lower the compression and run higher boost than run higher compression. also you can run pump gas on the lower compression motor.
I just built an LS2 @ 9.0:1 with 10 PSI SC, and pulled 535 WRHP before I ran out of fuel. just have to upgrade thefuel pump and should be able to go over 550 WRHP.
Hope this helped
Al
Just like Al said, you, you just have to be much smarter about it. I read somewhere that some of the big turbo drag guys are running 10ish. I think a lot of people drop their compression way too low but 9 - 9.2 is a good balance of pump gas reliability and decent boost performance. Higher compression also makes the car more responsive when not under boost.
Why compare the CR of a race car that runs C16 fuel and has every pass data logged and reviewed extensively to a street machine that runs on pump fuel?
When I asked W2W, Lingenfelter, etc what CR I should aim for on my forged LS6 turbo motor they all said 8.7 - 8.9.
When I asked W2W, Lingenfelter, etc what CR I should aim for on my forged LS6 turbo motor they all said 8.7 - 8.9.
I'm not, I'm just saying they do. You don't need to be a 6 second car to run more than 8:1 compression. Lingenfelter told you to run 8.7-8.9? I said 9 - 9.2 for a street motor in my post above. Splitting hairs as far as running pump gas on a low boost setting but it will be more responsive when not under boost and extract a little more power at the same boost level.
Most engine builders I've talked to recommend low compression to add some margin of error for those with more dollars than sense when it comes to running FI cars.
I guess I'm saying there are points of diminishing returns on each side of the compression range for FI.
Most engine builders I've talked to recommend low compression to add some margin of error for those with more dollars than sense when it comes to running FI cars.
I guess I'm saying there are points of diminishing returns on each side of the compression range for FI.
thanks for all the info and i understand all of it now, but only one thing. the S7 is a high compression TT, and its recommended fuel is 92 octane. i dont get that. any reasoning?
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