Compression test

[Jackson1320]

A compression test was only used when I was at the track to check if I had a dead cylinder. The actual compression number wasn't that important. Finding one cylinder which was like 90 and the others were 160, that's was a problem to send me home. To troubleshoot a dead cylinder, I would perform a leak down test which was the only test that mattered. The actual compression test psi numbers really didn't matter. I mean those numbers can be drastically changed by holding throttle closed, partly open or fully open. Spraying a few squirts of wd-40 would also make those numbers differ. Good Luck

Obviously the leak down test was not the only test that matters because the first test you did was a compression test. So if they all test the same you would go right back out and race. So if they all tested at 130 you would have gone out raced and forgot about it when your engine is wearing out for some reason that you don’t know or didn’t care to check because all the cylinders are wearing out evenly. Now you need a new engine all because you did not know what the test should have told you.
that’s like getting blood work and having your mechanic tell you if you are healthy. How the hell would he know because he doesn’t know what the test should look like

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[DougS550]

Obviously the leak down test was not the only test that matters because the first test you did was a compression test. So if they all test the same you would go right back out and race. So if they all tested at 130 you would have gone out raced and forgot about it when your engine is wearing out for some reason that you don’t know or didn’t care to check because all the cylinders are wearing out evenly. Now you need a new engine all because you did not know what the test should have told you.
that’s like getting blood work and having your mechanic tell you if you are healthy. How the hell would he know because he doesn’t know what the test should look like

Have Fun

 

[Jackson1320]

Have Fun

I’m just trying to show you that a compression test has its place and that sometimes it pays to know what the compression should be. If you’re way works for you that’s fine. There’s nothing wrong with that. But there’s always another way.
You should try being more open minded

 

[Jackson1320]

There are too many variables to get a hard number between cars without standardizing things. Compression test are like dynos. Everyone of them will spit out a different number.

Another thing people don’t think about is gauges freezing. A little bit of moisture in a the gauge brass pressure orifice that freezes will ruin it. Most gauges have a stop pin at zero than it can still show zero but be off serval psi after a freeze. Water can stay in a small gauge hole for a long time and anytime you compress air you will end up with moisture.

We are not talking about a compression test for NASA. Just trying to get a idea for what the average is

 

[Jackson1320]

-+10% Between 200-240 or do you want more NASA like numbers?

That’s what I’m looking for. Only problem is that I have other source that is very different, like 160. That is why I was asking everyone what they have seen. With as many people as possible contributing their will start to be a accurate trend

 

[cbrtrx]

That’s exactly what I’m saying. Just because the numbers are even that doesn’t mean that the engine is healthy. So if someone does a compression test and the numbers are all even they might think that the engine is healthy when it is not. So it is a good idea to know what the Engine should test at

I think it would be pretty uncommon to have all 8 cylinders equally as worn or damaged. I've tested many gen 1 and 2 cars, all had relatively low compression when tested but all ran very well. Just my experiences.

 

[engineermike]

@cbrtrx I would say 90+% of the time you are correct. In almost every case for me it was obviously good or obviously bad, with one exception. 1995 civic had 20-30 psi in all cylinders using 3 different gauges. It didn’t run either. It’s a really bizarre story that most wouldn’t believe, but at the end the car ran fine with 100+ psi on all 4. I believe the rings were carboned up and stuck.

 

[sigintel]

@cbrtrx I would say 90+% of the time you are correct. In almost every case for me it was obviously good or obviously bad, with one exception. 1995 civic had 20-30 psi in all cylinders using 3 different gauges. It didn’t run either. It’s a really bizarre story that most wouldn’t believe, but at the end the car ran fine with 100+ psi on all 4. I believe the rings were carboned up and stuck.

Lol. Thats awesome.
Kingsford or Royal Oak ring mod FTW!

 

[engineermike]

Lol. Thats awesome.
Kingsford or Royal Oak ring mod FTW!

Shoulda seen our faces when it started during the compression test with no distributor cap!

 

[JPSTANG]

If you want numbers an how I did it here ya go. 210 to 215 on all cylinders here. All plugs out throttle closed and fuel pump fuse pulled. Right or wrong it's all within the magic percentage I think.

 

[Jackson1320]

I think it would be pretty uncommon to have all 8 cylinders equally as worn or damaged. I've tested many gen 1 and 2 cars, all had relatively low compression when tested but all ran very well. Just my experiences.

But what is considered low?Because the dealer says 160 I perfect for a gen1 or gen2. So what are you considering low? 120?110?130?
It’s not uncommon for all cylinders to wear pretty ever on vehicles running no air filter

 

[Jackson1320]

If you want numbers an how I did it here ya go. 210 to 215 on all cylinders here. All plugs out throttle closed and fuel pump fuse pulled. Right or wrong it's all within the magic percentage I think.

Thank you

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