Average compression?

[aaddzz123]

Hi guys and girls! How are we on this fine evening?

Just done a compression test on my GT (at running temp) after a long year of hard abuse with no issues and the results came out at (about) 115,125,125,125...

I know this is low, but any ideas why? She runs like a beaut. Was wondering maybe I was lucky enough to have some lower comp pistons but standard HG and I don't think anyone would ever do a build and put a stock gasket on and no typical "tappy sound" on start up so... lol.

[funny onion]

My compression is around that mate, done several compression tests when I've killed it various times but compression has always even a steady 11.5-12 across all cylinders.

[aidanep71]

did u do it with the throttle wide open

[morgey]

11.5-12? Guessing you mean in bar?

which would be closer to 175-180 psi which is what aaddzz is done in

[funny onion]

Oh I read it as if he'd put decimal points in between, my bad. Yeah mine is roughly 180psi (give or take 5 or 6 psi) which does make that seem a bit low.

[aaddzz123]

Throttle closed... Wasn't aware it made a difference?

Yeah in bar it was about 8,9,9,9... Runs fine though. Couldn't just be wear at that extent?

[morgey]

If the throttles closed its trying to draw air in thru a small space, so wouldnt be able to get enough air in in time creating vaccuum basically, try it again open, might be suprised with the difference it can make sometimes

[starletburkie]

shit readings mate, do it again with wot and see your readings then..

[AdamB]

Warm engine and WOT ;)

Sounds about right though for throttle closed, should be up around 150-160 with it open.

Generally isn't that much difference between having the throttle opened or closed, its more important that the numbers read within 1 bar (14.5psi) of each other.

Edited August 3, 2012 by AdamB