View Full Version : Compression Test Results

12th December 2000, 09:36
No 1 - 162
No 2 - 160
No 3 - 163
No 4 - 162

Spot on then!


12th December 2000, 11:44
Ha ha! I got:


That's how we discovered that I had cracked a piston!

13th December 2000, 13:04
My last set of results were:


Oooops :) That's how I discovered that No. 4 piston had suffered a ring and ring land failure. Upon closer inspection it was clear that it had been like that for quite some time. Just shows you never can tell what you'll get when you buy a second hand engine!



13th December 2000, 19:17
Isn't it amazing that these engines can run with broken bits in them! That's exactly what happened to my piston Pat - broken ring lands which were still being held to the piston by the rings! The car still drove beautifully, the only problem being excessive amounts of oil in my catch can.

Bob Rawle
13th December 2000, 21:40
Interesting, my car tested


Subaru standard turbo spec is 146 to 175 with no more than 7 psi between cylinders. Minimum pressure 138 psi (wear limit. Subaru state that this should be checked with engine hot, all plugs removed, injector connectors removed and throttle wide open while cranking.

Quite a difference in range and tolerance. Would explain why cars can be so different in tuning terms.

14th December 2000, 11:25

Mine was running OK, if you ignore the fact that in smoke terms it was putting busses to shame! LOL. No oil control on No. 4 made it blow a lot of smoke out of the crank case... I do not run a catch tank, I just have filters on the breathers, so a lot of smoke from under the bonnet (not the exhaust as would otherwise be the case, well if running normal breathers anyway).


a good set of compression figures, sounds quite healthy (but then so were my 1-3...). Perhaps your figures are higher because it's a 5 door (the engines were, allegedly, different to the 4 door)?

Interestingly, the crowns on my original (dead) STi II engine look absolutely perfect, and in the failed No. 4 cylinder (where a conrod disintegrated!) there is no sign of scoring on the bore, indeed the bore looks perfect. It's just that the piston requires a mallet to move it! :) Still trying to figure out why this one failed... pretty much figured out why the replacement failed [thanks again for your time looking at the damage on that one! :)]



Simon Roe
14th December 2000, 12:49
Two engines both with number 4 piston rings going.... coincidence or a possible weak point?

14th December 2000, 17:26
Pat, on my dead STi Ver4 engine also the cylinder 4 failed, my pistons were fine (although this one didn't move), but the conrod was destroyed, and the bearing between the conrod and crank dissapeared........only possible causes i could think of were:
a) Changed engine oil brand before engine failed
b) Here in Peru we have 97 RON fuel, so because it is a Japaneese spec STi car it could have had knocking problems (at the time i didn't have a knock or lamda link to monitor the engine)
BTW my car was running completely stock......