7 UP 1

I am not a guru at F/I so I am going to ask this question and see maybe if there are some of you out there. I figure that the higher boost you want to run the lower you want your engine compression. Is this right? But on the flip side is there a point where you can lower your compression too much? I met a guy with an older chevelle and he rebuilt his engine with a 6:1 compression with 26lbs. of boost from a turbo. This car was crazy fast but got awesome gas mileage as well. has anyone tested compressions and boost mixtures on the 5.0 and what seem to be the best numbers for this motor? thanks

luckythirteen13

i wouldnt go less then 8:1 on a boosted motor. i run 9.5:1 with 10psi of boost. 6:1 is rediculously low even for 26psi. maybe he was trying to stay on pump gas

2 kwik

yeah but I bet that engine was a big block
I run flat tops and 15=16 psi timing at 10

7 UP 1

the motor he was running was a chevy 327

2 kwik

damn he needed 7.5's in that thing

MadMan@TheWheel

I am not sure anyone on here will state that they are experts, so don't feel bad. Factory pistons will easily support as much as 12psi, it seems the issue with excessive boost is never how much is too much as much as it is how much do you want to spend. I do agree that 8:5:1 is a comfort zone that is good to abide by if you are anticipating large amounts of boost, understanding that to support the amount of air you are feeding the motor the more fuel and of course exhaust velocity you will need to build the HP you are paying for. If you look at numbers on cylinder pressure related to nitrous they get very high, but is instantaneous, so no matter how you decide to go, past a certain point you will need to decide how fast and how much money you need. But your current comp. can handle quite a bit. At least 10psi.

Just my view

SpooledupRacing

with lower compression u can run higher boost levels YES! however with a great tune anything is possible..

another spectrum but take diesels for example.. 20:1+ compreression ratio with a blower (upgraded at that) and 60+psi I mean it can be done it is all in the tune however..

I would not go any lower then 8:1 on a V8 however 8.6:1 would be the magic number for 15-20psi with a great tune..

same goes with pistons.. alot of people think u HAVE to use forged pistons if u are boosting.. not true.. cast or hyperutectic pistons will be fine however they have a higher possibilty of explosion IF/WHEN u detonate

Dave

Derf00

There is a thing called the law of dimishing returns. That is, you can only lower your compression so far to add boost before you end up making less power with more boost vs slighlty higher compression and lower boost

In other words, 6:1 compression plus 26lbs of boost is probably going to yield less power than 8.5:1 w/20lbs boost.

SpooledupRacing

100% correct thus back to why I stated I woudl not go any lower then 8:1 but perfer 8.6:1

Dave

Bad Karma

+1
-Ivan