I'm no boost guru, but this question has been bothering me for a while now. Why not run a higher compression, and less boost? Wouldn't be the same? I know there's a technically answer to this, so let's hear it.
a lower compression engine with let say 6 psi from a T3 super 60 will have less power than high compression with 6psi.
the main thing is it's easier to tune. Less problems(detonation and pre-ignition).
Or if you go with alot of boost then you need to lower the compression.
Gilles
2.3 Ho
Quote:
a lower compression engine with let say 6 psi from a T3 super 60 will have less power than high compression with 6psi.
My point exactly.
Quote:
the main thing is it's easier to tune. Less problems(detonation and pre-ignition).
Won't you run in to those same problems at higher boost? Let's you have two identical motors ( Same amount of fuel, same spark). One is high(or stock) compression running 6 psi and it's detonating. The other is low compression running 12 psi (Or significantly greater than 6). Isn't this one going to detonate also?
In a way, a turbocharger increases compression, correct? So why not keep "piston" compression high, and just run less boost? Does the increased volume in the combustion chamber of a lower compression motor make more power than a higher compression, less volume motor?
Because dropping compression a few points lets you run a quite a bit more boost, thereby making more power than you're losing.
It's all a matter of heat in the combustion chamber - less compression lets you run more boost because it gives the cylinders a cooler environment in which to make power..
Consider this:
9.5:1 compression bumped up to, say.. 10:1 compression. Let's say you make an extra 30 horses and run a "safe" 4-5 lbs of boost.... so you make what.. maybe 70 hp over stock?
9.5:1 compression dropped to 8.5:1 - Let's say you lose about 20 horses but now you're able to run a "safe" 15 lbs of boost.... so you make... (guesstimating here).. 120 over stock.
I'm being conservative.
The reason the lower engine can run 15lbs is because of the cooler cylinder temps, and the ease of tuning a higher PSI turbo setup in this more accomodating environment.
This is why people drop compression - others opt to run the highest octane gas they can to avoid pre-ignition. You can, of course, do both.
-Chris-
-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
^ he's right.
I run 9.63 of compression with my T3/T04E because I wanted an engine that I could still build N/A and have descent power in case I take off the turbo.
Gilles
2.3 Ho
It all makes sense now. Thanks guys
SunfighterGT wrote:Because dropping compression a few points lets you run a quite a bit more boost, thereby making more power than you're losing.
It's all a matter of heat in the combustion chamber - less compression lets you run more boost because it gives the cylinders a cooler environment in which to make power..
Consider this:
9.5:1 compression bumped up to, say.. 10:1 compression. Let's say you make an extra 30 horses and run a "safe" 4-5 lbs of boost.... so you make what.. maybe 70 hp over stock?
9.5:1 compression dropped to 8.5:1 - Let's say you lose about 20 horses but now you're able to run a "safe" 15 lbs of boost.... so you make... (guesstimating here).. 120 over stock.
I'm being conservative.
The reason the lower engine can run 15lbs is because of the cooler cylinder temps, and the ease of tuning a higher PSI turbo setup in this more accomodating environment.
This is why people drop compression - others opt to run the highest octane gas they can to avoid pre-ignition. You can, of course, do both.
-Chris-
^^ This is some very good & usefull information this should be in the Stickys!!! ^^
Now it all makes sense why you lower your compression for boost & nos.. Makes complete sense! If i ever have any questions Im consulting you! LOL haha
Faith is to believe what you do not see; the reward of this faith is to see what you believe.
-Saint Augustine
