Thread: Should I go 9.5 or Stay 8.5

GTiR T28, currently 370cc's. I was at past 80% on them at 4 bar (420cc) at 7ish psi.

I have always done 9.5 except the VE which is 10.3..just get the 10:1 block from Keo.

personally ive always said the larger the boost the lower the compression with a few exceptions. personally i think you can go 9:5:1 and have no issues at all with any boost level, its when you get to the 10:s where you gotta get a little conservative, however alot of honda guys make over 300whp on 10:1 compression engines. the lower the compression is just going to let you be a little less conservative on timing and a little bit more agressive.

10:1 would be fine for his setup. The honda guys have much better resistance to detonation due to combustion chamber design. It is a whole different story so that doesn't really apply to the sr20 compression ratio discussion. As long as the tune is good and the boost doesn't go above 10psi with those injectors he will be fine.

When ever I get around to building a block a ground up I will do 9.5:1. 10:1 is a little high for daily I would say. Plus this is my road trip car (Yes I like to drive my turbo car on long trips, helps with traffic ), so it would be safer with crappy gas.

Then again 8.5:1 might be even better in that case. I guess it will depend on my funds and free time .

well its all in the tuning period when its all said and done. more so with the iginiton map.

Yes that is true, it is all in the tuning. Still doesn't mean the Honda's won't have better resistance to detonation.

I would do

9.5 to 1 compression DE pistons Swain Coat the tops ( dont forget to notch the piston for oil squirters )

S15 480cc injs @ 4 bar ( good for 340 WHP )

Maybe even get a GT28RS .86 AR ( run it at 12 PSI all day every day ) 330 WHP @ 300 LB Ft Torque