Compession test

trueno_20v · Post by **trueno_20v** » Wed Apr 12, 2006 6:12 pm

Done a compression test on my silvertop 4age today and got:

160 150 160 160 psi

sound right??

i wound it over about 4 times maybe it wasnt enough?

Jebus · Post by **Jebus** » Wed Apr 12, 2006 6:35 pm

Pretty good

matt9ball · Post by **matt9ball** » Wed Apr 12, 2006 7:28 pm

i got 175 180 175 170

matt9ball · Post by **matt9ball** » Wed Apr 12, 2006 7:31 pm

sorry just checked i actually got 170 175 185 185 psi

Malcolm · Post by **Malcolm** » Wed Apr 12, 2006 7:36 pm

main thing you're looking for is variation, they should all be within about 5% of each other, 5% of 160 is 8, so your minimum should be 152, I'd say you're probably fine, might have slightly worn rings or maybe just did a bad test. I wouldn't be concerned unless you're having overheating problems

AE85coupe · Post by **AE85coupe** » Wed Apr 12, 2006 8:36 pm

wow thats really interesting, my smallport has 250psi across all cylinders

surprises me how much more pressure i seem to have

Punter · Post by **Punter** » Wed Apr 12, 2006 8:40 pm

AE85coupe wrote:wow thats really interesting, my smallport has 250psi across all cylinders

surprises me how much more pressure i seem to have

It can vary hugely, ie throttle open or closed, cam overlaps/timing etc. etc. Infact 4afes will sometimes test higher than 4ages.

AE85coupe · Post by **AE85coupe** » Wed Apr 12, 2006 8:49 pm

Punter wrote:
AE85coupe wrote:wow thats really interesting, my smallport has 250psi across all cylinders

surprises me how much more pressure i seem to have

It can vary hugely, ie throttle open or closed, cam overlaps/timing etc. etc. Infact 4afes will sometimes test higher than 4ages.

yeah that makes sense, i wonder what smallports usual compression is

trueno_20v · Post by **trueno_20v** » Wed Apr 12, 2006 9:14 pm

well i done mine with open throttle..

craigt · Post by **craigt** » Thu Apr 13, 2006 10:39 pm

Actual readings between different gauges cant be compared. They all read differently, whether its because of design or gauge calibration, I dont know.
Compression tests are only useful in comparing the readings between cylinders.
I actually quite like leakdown tests but they are a bit more time consuming to do.

CAMB01 · Post by **CAMB01** » Sat Apr 15, 2006 6:03 pm

i have 180psi across the cylinders on my GZE