What is the acceptable variance between the wet & dry compression test?

For the wet test, I used about 3/4 cap full (small cap - about the size of a 20oz soft drink, not the big caps on Mobil 1). Test was conducted about 5 minutes after about a 30 minute drive on the highway.

On with the results:
Dry: Wet:
#1 240 265
#2 245 273
#3 235 251
#4 243 280

 

Dry looks really good as the variance between them dry standard limit is like 20psi so that is good. The wet will vary as the oil will not go around the cylinders equally. Also, why did you do the wet as there is no great variation. Make sure the car was warm and the throttle was all the way to the floor when doing this.

You add oil to check the rings if you get a low cylinder. If after the addition of the oil the cylinder pressure increases substantially then most likely the rings are bad on that cylinder.
Are you getting a fluctuating idle, smoke, bogging etc... ? is that why you initiated the test?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drintegra &raquo;</TD></TR><TR><TD CLASS="quote">Dry looks really good as the variance between them dry standard limit is like 20psi so that is good. The wet will vary as the oil will not go around the cylinders equally. Also, why did you do the wet as there is no great variation. Make sure the car was warm and the throttle was all the way to the floor when doing this. </TD></TR></TABLE>

Variance between the cylinders is in spec, and I am happy with "those" results. I did the Wet test because my car loves to drink oil. I thought I had bad valve seals because of smoke during downshifting and accelerating, and therefore opted to go for a ported head with new valve seals. Oil consumption had not changed. ~1 qt/ 400 miles.

Throttle was open all the way and the car was still pretty hot when I conducted this test.

 

1qt for every 400 miles sounds how my car was before the rod bearings were pounded out.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowsi00 &raquo;</TD></TR><TR><TD CLASS="quote">1qt for every 400 miles sounds how my car was before the rod bearings were pounded out.</TD></TR></TABLE>

Can you include more details? I'm very interested.

 

 

I'm seeing HUGE differences in compression numbers from Wet/Dry tests from others when the rings are done.

Maybe I should try more oil for the wet test? I guess I should have put 2 & 2 together and realized that it is helping it seal... maybe I should wait a minute or 2 before I crank the motor so the oil can go more to the outer edges of the piston?

Has anyone done a compression test (wet & dry) for a motor that is perfectly healthy? No oil consumption, good power, no issues?

 

what compression is your motor?

 

Eleven & a half to one.

 

either way, your compression results are pretty good. Id stop worrying about it. Did you do a test when the motor was first broken in?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by adictionbass &raquo;</TD></TR><TR><TD CLASS="quote">either way, your compression results are pretty good. Id stop worrying about it. Did you do a test when the motor was first broken in?</TD></TR></TABLE>

Unfortunately, I did not do a compression test when the motor was first broken in.

But I do have to worry about it because this motor is eating 1 quart of oil roughly every 300-400 miles. I've had 2 heads on my car with new valve seals. The first one looks like it had too much play in the guides, but this new one has been spec-ed, and it also has new valve seals.

 

do you have any kind of catchcan on it?

 

endyn catch can with no drain-back. Also feeding the valve cover nipple into one of the hoses that lead to the catchcan as well... open element filter on the can, no PCV.

 

well your in the forced induction section so i want to assume turbo, but thats really high compression... If so, turbo seals maybe?

 

I have not gone forced induction yet. I was planning on going with a JRSC, thought I'd get comfortable here

Looking for basically a very linear powerband motor to do some triple duty.

 

 

 

so get a small turbo, more efficient then the supercharger with room for improvement. How much oil you wasting now?

 

1 qt / 300-400 miles. dino, syn, 5-30, 10-30, 10-40, 10-60, 15-50, 20-50... my car doesn't discriminate.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Takumi Fujiwara &raquo;</TD></TR><TR><TD CLASS="quote">I'm seeing HUGE differences in compression numbers from Wet/Dry tests from others when the rings are done.

Maybe I should try more oil for the wet test? I guess I should have put 2 & 2 together and realized that it is helping it seal... maybe I should wait a minute or 2 before I crank the motor so the oil can go more to the outer edges of the piston?

</TD></TR></TABLE>

I was also wondering if the differences would be higher if you used more oil. Sorry can't help much but interested to see your findings.

 

did you do a leakdown test? it is a little more complicated then the compression test but will let you know if you are leaking from the valves for sure.