Alright so I did a compression test recently.

I followed the write up in the how to/installing forum.

First off I have a stock EVO 8 motor with 64k. Car has seen power in the 460whp range for about 20-30k miles.

Warmed up the engine to operating temperature, pulled all the spark plugs, and performed the test with 7 cranks for each cylinder.

Using my snap on compression tester I did 1-4. All number were within 1-2 psi of each other.

My numbers were 120-122 psi. I should also mention im at 5400 ft above sea level, so im not sure what difference that might make.

I read about some people's levels and mine seem really really low so im just wondering is this bad or how much does the altitude affect compression.

 

wow, i thought the lowest possible reading was 135... Someone help this guy. i have an evo 8 with 73k and numbers where 150 155 160 160.

 

Dealer says they should be within like 12psi from 135-170 i think.

 

seems a bit low, even for the altitude. Do the check again with squirting some oil in the cylinder. crank the motor a few times then test. If its huge jump then you need rings. If not then its what it is. Since all cyl. are similar your head and valves are good.

 

make sure you have the throttle wide open when u test

 

Well if your running aftermarket cams, or cam gears tweaked, then you will need to run a Leak down test to see if you really do need a rebuild as a non-standard cam timing will change what good compression numbers actually are.

 

No throttle or wide open didnt make any difference. Maybe like 1 psi if I remember correctly.

I'll wait to hear some more input and talk to some more vendors then I'll try to check the rings.

 

Try cranking the engine over till the gauge stops moving....it usually takes more then 7 turns.

 

I just did mine at 6000 feet and they were 110 across with Cossie M2's.

-E

 

sounds pretty low

 

The main thing is that it's consistent. I got in the 180's +- a few psi a few days ago. '05 with basic bolt ons, S2's and 43k miles. 10 cranks a cylinder with throttle closed but that probably doesn't make a difference.

 

yes it will make a difference...and make sure your car is warm

 

They are consistant, low not so sure. I would do a leak down test also. If the car is not burning oil and running well then I would say your numbers are good. See if you can find another stock motor member near you and compare numbers to see if you are in line. Call a local shop and ask them what numbers they get on a stock motor. I bet you are good.

 

Umm... Car was warmed up to full temps. Not warming up the car would lead to lower psi. A friend of mine checks his compression the same way as me and only got into the 160's with his '05.

 

It is the altitude....Had you been at sea level they would have been fine....See Boyle's Law for details....It is excellent they are all about the same...