AaronJ

iTrader: (12)

Ok, so im looking at buying a halfbridge rx7 but we ran into one small problem. We did a compression test and it ran 90 psi on both faces. Im looking to see if anyone has had an similar experiences with half bridge motors. Please post up what type of numbers you have seen first hand? I would appreciate all the help i can get right now

Thank you

peejay

Depending on the tester and the port, that's pretty good.

A longer hose makes the compression lower. My compression tester has a 2' longer hose than my co-worker's and his gauge consistently reads 10-15psi higher than mine.

Intake closing time has an effect on compression. Ignore overlap, overlap has zero effect on cranking compression, cranking compression is 100% intake closing time, compression ratio, and chamber sealing. A late closing port will have a lot lower compression than one with stock-like closing.

I wouldn't frown on 90psi. I've had freshly rebuilt engines that would only do 90psi. My current engine did about 105-110 with VERY tight seal clearances that you wouldn't really want to run on a turbo engine. It currently does about 75 front and under 40 rear because the chrome is badly flaked from the rotor housings...