i wanna put turbo on my B16a2 hatch the compression ratio on the motor now is 10.4:1....do i need to lower the compression ratio? and how would i do that? what is the ideal ratio for turbo?any answers? thanks

 

thats a tough question...

simple answer: Depends on the amount of boost. The higher the boost the lower the compression should be. I'd recommend lowering the compression to maybe 9-something:1 for about 6-9 lbs. of boost(many different factors). It can be lowered by things like changing the head gasket and pistons(i think) and other things.

 

it all depends on what you want. if you want to brag about the amount of boost you run, or you want a car that has big peak HP numbers, then go ahead and lower the compression. if you want a quick spooling car that pulls all the way to redline, keep the stock C/R and set the boost low, like 4-6 psi and get some bigger injectors, im going with 380cc s2000 injectors. the high compression will spool the turbo really quickly. a turbo car only has the NA power to use until the turbo spools, so if you lower the compression then you have a slow car unless you are making boost. also, the high compression ratio speeds the exhaust gas on its way out, thats where you get the quick spool. and if you decide to lower the compression, dont just use the head gasket. it ruins the cylinder head chamber design and will make the motor more prone to detonate. lowering your CR with a gasket to 8:1, gives you the detonation resistance of about 9.5:1. so its very counterproductive. oh yeah, run an intercooler.

 

ok so should i lower the CR or not? would i be better off with a lower compression and more boost or stock compression and less boost?

 

like sac said, that depends on what you want to do.

 

personally, i drive my car everyday, and i would rather have a quick spool than big peak HP, so i dont have to redline it whenever i want a little power. i am going with a b16 head on my jdm gsr block, giving me 10.3:1 and im going to try to tune it with a fuel pressure riser and S2K injectors with a Greddy turbo kit to about 4-5 PSI, then have another fuel map set up for race fuel to run up around 8-12 psi.