I don't want to sound stupid but I want to know:
What exactly is compression, and why is it important for boosting ?
Compression ratio....etc.

 

compression ratios are important for boosting because if your compression is to high then you can create detonation. the way the engine works is
1. at the bottom of the pistons stroke it has pulled in a mixture of fuel and air at a certain temperature.
2.then the piston starts to compress this mixture on it's upward stroke.
3.as the piston compresses the mixture, the temperature of the mixture rises.
if the temperature is too great, the mixture ignites before it reaches top dead center and that is what is called detonation. very bad for the engine.
when boosting, you are using a greater volume of air more likely to detonate during the compression stroke. by lowering the compression ratio, you are basically lowering the amount that the mixture is being compressed. if you're ever bored you can pick up a thermodynamics book that will explain it all with equations and engineering knowledge. hopefully that is the answer you were looking for.

 

well static compression (what you start with) and dynamic compression (after your boosted) ends up being alot higher, thats essentially the only way to gain HP by increasing your compression so whether you start with alot or not, its what you end up with is what matters and if your engine can take it at high rpm. Alot of people say lower compression is better when turboing but I cant really remember at this moment.

 

we all have to learn sometime right? dont feel bad dude.

if you have 10:1 pistons (stock 5th gen) then think if it like this.

when the piston is at BDC (bottom dead center) it has 1psi of air in the cylinder. once the piston moves upward to TDC (top dead center) it has now compressed the 1 psi to 10 psi.

when you boost you want to lower your compression ratio so that you can add more air safely. boosting is just forcing more air into the same ammount of space. if you put too much air in there then it will want to escape somehow. be it the ringlands, valves, cylinder wall whatever. it will blow something because there is too much air in the little area. that is why you "bulletproof" your engine with say darton sleeves or something like that (and many more parts!!). just remember nothing is idiot proof.

HTH!

 

Thanks for all the replies just what I was looking for

 

might be ot but. has there every been such a thing as..say 10:2 where it has higher pressure in the cylinder? ive noticed no one sells such a thing so i assume its not good, but what would it do?

 

10:2 would be 5:1 ... right?? I think they evaluate it that way..

 

yeah, it's a ratio, which is just like a fraction. 10/2 is the same as 5/1.

 

Very good explanation guys.