Hi can anyone tell me wot sort of compression test figures i should be getting from a standard impreza sti version 5 engine with 61k on it? Are the figures lower on the turbo side of the engine, cylinders 1n3? Cheers Steve.

 

Compression with the throttle fully open and all plugs removed cranking at 200-300 rpm.

std 146 to 175 psi (10.1-12.3 bar)

wear limit (worst ... 138 psi (9.7 bar)

this is the important bit ... difference between all 4 cylinders 7 psi (0.5bar) max.

so whatever level they are at the differential applies.

so no cylinders 1 and 3 "should not" be lower in that sense.

the wide range reflects the compression ratio tolerance of 7.8-8.2 to 1

bob