compression for turbo + or - = ???

[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...