Well I ran a compression test today on my jdm h22 and it came out 168,170,174,168. But I did cylinder 2 with the car on and I got 50 at idle and 45 at 3k rpm. Someone told me 50 was too low. So I did a test on a friends ls integra. He had 125 psi cranking and about 55 psi running so I know something is not right with my compression. The car drives ok though I did the test cuz it was part of my school work. Anybody got opinions?

 

wait.....you did a compression test with the car running? seriously

 

Yeah I did both a cranking test and car on test. My professor told me to do it but he didn't want to tell me the purpose. He was the one that told me the numbers were low.

 

I have NEVER heard of doing a compression test with the car running. You're supposed to take out all of the spark plugs from all the cylinders when doing it correctly.

Your going to flood that particular cylinder while doing it (fuel is still flowing).

Make sure you take out the ECU Fuses while doing a compression test.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by redline7 &raquo;</TD></TR><TR><TD CLASS="quote">Yeah I did both a cranking test and car on test. My professor told me to do it but he didn't want to tell me the purpose. He was the one that told me the numbers were low.</TD></TR></TABLE>

He probably wanted to see if you'd actually go through with it!

170's is fairly low for a JDM H22. But they're within 10% of each other, so that leads me to think you have a bunch of miles on it or it needs a refresher tune up.

 

my h22a has 230ish across all four with the engine off.
I strongly suggest askin him why u would do it with the engine running?
I've never EVER heard of such craziness.....

 

its called a dynamic compression test I did it in school
and it is a valid test

 

so basically you are running the engine on 3 cylinders while the engine constantly pumps itself on the dead cylinder?

How is this any different than a typical compression test?

 

hmmm.....interesting

http://www.imperialclub.com/Re...c.htm

 

nice thanks for the link

i could see a lot of uses for doing the dynamic test and not just diagnosing engine health.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jago &raquo;</TD></TR><TR><TD CLASS="quote">its called a dynamic compression test I did it in school
and it is a valid test</TD></TR></TABLE>

Thanks for the help. everyone online and in my crew was looking at me like I am a idiot thats gonna blow my motor apart.

But anyways I found out that when I did my crank compression test I was suppose to take out all the spark plugs and go WOT in which I didn't. So I did it again the right way and got almost 240 psi right across. Now I need to find out how to convert that to a ratio.

 

your compression ratio is already well known. dynamic compression is determined by the camshaft and in most cases is somewhat useless information. what are you trying to figure out here?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 95greenlude &raquo;</TD></TR><TR><TD CLASS="quote">hmmm.....interesting

http://www.imperialclub.com/Re...c.htm</TD></TR></TABLE>

another example of useless internet crap. they dont even know how to add pressures and people are taking this as intelligible information.

 

Do you go to UTI?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bluedlude &raquo;</TD></TR><TR><TD CLASS="quote">

another example of useless internet crap. they dont even know how to add pressures and people are taking this as intelligible information.</TD></TR></TABLE>

how is it not useful?

 

in the end what will doing this test get you, just some numbers. dynamic compression will vary depending on what engine mods you have and the condition of your intake/ exhaust tract. if you have a bent valve or poor valve seal your dynamic compression will lower but how can you tell unless you did this test on a brand new motor. in the end a standard compression test and leakdown will give you more usefull data than this ever would.

do you trust someone who thinks that 30 - (-18) = 12 ? because I don't

 

i was thinking more along the lines or being able to test different engine parts (with the same gauge) to determine what gives the highest dynamic reading.

 

well a cam with short duration may show a higher dynamic compression than a cam with longer duration but it won't tell you which will make more power.

 

its still not COMPLETELY useless to someone who can actually derive some meaning from it

 

Well I see I started a war here...ok here is a thought...does the motor have the same amount of vaccum at idle as when cranking? If not then one could use this test to see if the vaccum is actually making it in into the cylinder at running rpm's such has 1000 rpm. We could measure the vaccum at the manifold but wouldn't it be better to test it at the cylinder?

Also I don't go to uti. I attend a community college as a automotive technology major. I am just not trying to be ignorant like some people here *cough*. Maybe I might learn something if I listen.

 

Yo, try this.

Do a normal compression test by disabling the IGN. and if possible, fuel too. (I find this easy by simply disconnecting main relay)

Then do a compression test as you normally would and record results.

Then, add a little bit of oil into the cylinder and do another compression test and record your results. Then post your results here.

When I did mine in school, i got about 190-190-195-185 on my cylinders and about 200-195-195-190 with the oil in the cylinder which means my engine is good since the numbers are so close and about average for a h22a1. It will be a little higher with the oil but it shouldn't be too high. What it does is if your combustion chamber is leaking compression, the oil fills those spots and gives you a reading. IF compression test w/out oil and w/ oil are relatively close, then your engine is good. If it goes from like 165 to 195 or something like that, you have a problem..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by prelude_93vtec &raquo;</TD></TR><TR><TD CLASS="quote">Yo, try this.

Do a normal compression test by disabling the IGN. and if possible, fuel too. (I find this easy by simply disconnecting main relay)

Then do a compression test as you normally would and record results.

Then, add a little bit of oil into the cylinder and do another compression test and record your results. Then post your results here.

When I did mine in school, i got about 190-190-195-185 on my cylinders and about 200-195-195-190 with the oil in the cylinder which means my engine is good since the numbers are so close and about average for a h22a1. It will be a little higher with the oil but it shouldn't be too high. What it does is if your combustion chamber is leaking compression, the oil fills those spots and gives you a reading. IF compression test w/out oil and w/ oil are relatively close, then your engine is good. If it goes from like 165 to 195 or something like that, you have a problem..</TD></TR></TABLE>

Yeah I didn't do the wet compression test cuz my motor was already making close to perfect specs according to my research. I can't imagine the cp getting much higher. If you didn't see I got about high 230's to 240 psi cranking

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">its still not COMPLETELY useless to someone who can actually derive some meaning from it </TD></TR></TABLE>

but then there's people that will try to do this and potentially harm their motor, or zap the **** out of themselves when they touch a ground and a plug wire too close to the end.

either way...this seems like it might be a useful test to some. I personally wouldn't disconnect the ignition and let the cylinder flood with fuel with no spark...but hey, that's just me.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by redline7 &raquo;</TD></TR><TR><TD CLASS="quote">Well I see I started a war here...ok here is a thought...does the motor have the same amount of vaccum at idle as when cranking? If not then one could use this test to see if the vaccum is actually making it in into the cylinder at running rpm's such has 1000 rpm. We could measure the vaccum at the manifold but wouldn't it be better to test it at the cylinder?

Also I don't go to uti. I attend a community college as a automotive technology major. I am just not trying to be ignorant like some people here *cough*. Maybe I might learn something if I listen.</TD></TR></TABLE>

i dont know about yours, but my compression tester only reads positive pressure. yes a motor at idle will have a higher vacuum than it does at cranking but what will your method show that a leakdown test will not? i am just trying to say that without some type of figure as a reference this is pointless. i guess I just have to wait for you to teach me something

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bluedlude &raquo;</TD></TR><TR><TD CLASS="quote">i dont know about yours, but my compression tester only reads positive pressure. yes a motor at idle will have a higher vacuum than it does at cranking but what will your method show that a leakdown test will not? i am just trying to say that without some type of figure as a reference this is pointless. i guess I just have to wait for you to teach me something </TD></TR></TABLE>

Ok u say there is no reference figures but there is. The website that is linked above says each cylinder should have about 50% cp at idle as when cranking and 80% cp when you do a quick WOT. According to the website if ur cp is not within these specs then you have a problem with air flow somewhere in the motor. Whether or not this stuff is really true for all modern day piston motors I don't know. So with my cylinder #1 producing about 238 psi cranking I should have about 119 psi at idle.