compression for turbo + or - = ???

[02_Si]

Does higher compression = more power? And what is a good compression for turbo? I think my car now is stock 9.8 @ 160hp... is this 9.8 compression too high if I ever want to add turbo?

[pdiggitydogg]

lower compression is better for boost
(thats why lots of people go b18b+boost when swapping motors)

lower compression means you can run higher boost w/o having to worry as much as w/ high compression (thats why its bad to boost type r motors...very high compression)

[02_Si]

I see... what does it mean when a motor detonates... does it actually blow up? Wouldn't that like, blow up your whole car?? ;(

[nonovurbizniz]

well... lower compression makes it EASIER to run higher boost... all you're trying to avoid is detonations which is also refered to as pinging.. it's pre-ignition.. as the piston rises and compresses the air/fuel mix.. sometimes things can lead to the a/f igniting befor the spark plug should ignite it... this on a NA car isn't the biggest deal in the world but if your car pings you have to correct the problem QUICKLY... on a turbo car it can send pistons or rods or headgaskets a-flying... YES it can TOTALLY destroy your motor...

whether high or low compression you have to retard the timing as the revs climb.. both because boost is rising but also becase at higher rpms there is a higher occurance of hot spots on the cylinder walls.. this is a MAJOR cause of detonation... besides too advanced ignition.

on high comp it takes a LOT more tuning and you're risking it more.. with low comp. you end up having MUCH less lowend and a decent amount less top end...

[02_Si]

what would be considered low boost and high boost (in psi?)

[02_Si]

oh yah, and what would be an ideal comp ratio for turbo?

[nonovurbizniz]

low is 8 or under... high is over 12. people run 20 or 30 sometimes even more.

ideal compression... it depends on who you ask.. most say under 9:1 lots do it with 10:1... usually 8.5:1.. that seems to be some sort of magic number (that's more general though) honda's probobly run a little higher than that.