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If i lower my compression from stock to 8.8:1 with pistons will my PSI also drop? i'm planning to run 12psi in the future. i didn't find anything in a search.
 

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i think it will "lower" your horse power, but youll be able to "turn up" the PSI while running the car safer
i think
 

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Your actual boost level has nothing to do with your compression ratio.

But, it is smart to lower your compression when you start pushing more boost.
 

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wxman25 said:
If i lower my compression from stock to 8.8:1 with pistons will my PSI also drop? i'm planning to run 12psi in the future. i didn't find anything in a search.
plain and simple no.
 

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like everyone said...

exept that you'll lose a bit of hp
 

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Then what exactly is the point of lowering compression... just for a higher number?
 

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komokazi said:
Then what exactly is the point of lowering compression... just for a higher number?
Depends on what you are looking to acheive and where in the powerband you want your power. Obviously a higher compression engine with lower boost is going to be in its power range quicker compared to a lower compression engine with double the boost.

Here check this out, this explains what I am talking about better: http://www.motorsportsdigest.com/tech/forced2.htm
 

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Compression ratio doesn't determine boost. The method you use to control boost determines this. If you run without any boost controller, this is adjusted by changing the wastegate actuator. For low boost and a small quick spooling turbo this is probably just fine. You can do this together with a manual boost controller to make small adjustments, depending on how you're tuning the car. Generally though, the wastegate actuator determines boost.

If you go electronic, then you can program a set boost level.

For a given goal on power, you need a certain amount of air, and a certain amount of boost. Eventually you just HAVE to run a lower compression ratio because of preignition or you can't keep the combustion process from spilling over into the exhaust (which doesn't power the car). I can't imagine you could get away with something like 1bar on the stock compression ratio. If it didn't preignite, you'd never be able to run enough timing. Your timing would be pulled back so far your gas and air would just be burning in the exhaust, not in the cylinder, doing you no good. Say, you could up from 12psi to 15psi, you'd find out you had to pull timing another 3 degrees to avoid detonation, but then that extra 3psi worth of air might just be cooking your exhaust manifold and exhaust valve rather than pushing the piston. You'd just hit a ceiling and either destroy parts or just have to back down.
 
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