2g turbo Compression Test results

[Blk95gs]

Hey all,

I performed my first compression test yesterday afternoon on my 95 TSi AWD w/ 125k miles with a friend of mine who has likely done this a million times. I wanted to ask a quick question about this.

Everyone I have ever talked to says that a 15psi variance between 2 cylinders could be a sign of a problem. We didn't do a wet test (where you put a capful of oil in the cyl and retest it) but the normal test showed the following numbers:

Testing from left to right... 180-185-170-175.

All of the plugs looked fine, none were fouled or anything like that. Now for the question I had.

I saw the 15psi between 2 cylinders, but my friend (who is one of the smartest people I've ever met) said that the 15psi would be determined if the optimal compression on the car would be 150psi/cylinder. So for engines that have higher optimal numbers, I would assume that the margin between 2 cylinders would be greater? 15psi is 10% of 150, so 10% of 178 (stock comp ratio on 2g 4g63-t) is obviously 17.8psi.

Is that assumption valid? I tried searching but really can't pinpoint an exact answer to this. I feel like the test shows very good numbers for a car of this age and mileage.

 

[Spln_Hrd]

Those numbers are great considering mileage. My 2g has 130,000 miles on it and I did compression test 2 days ago.

152 143 148 158

 

[blcknspo0ln]

Those numbers are great considering mileage.

Agreed. You don't have anything to worry about with those type of compression numbers.

 

[Blk95gs]

That's what I had figured. It just almost seems too good...you know what I mean? The previous owner tested it about 8 or 9 months ago (I bought it in Sept.) and said that he got the EXACT same numbers, but I wanted to test it for piece of mind.

I must be an idiot for selling it then.

 

[blcknspo0ln]

That's what I had figured. It just almost seems too good...you know what I mean? The previous owner tested it about 8 or 9 months ago (I bought it in Sept.) and said that he got the EXACT same numbers, but I wanted to test it for piece of mind.

I must be an idiot for selling it then.

Perhaps you are, perhaps you aren't. Either way, sell it to me

 

[CanadianTSi]

Your perfectly fine.

Your only down 8psi in one cylinder...nothing to worry about, the other 2 are high from carbon buildup...

 

[Blk95gs]

The one cylinder that was 8psi lower had some oil on the plug. It was on the threads, and it was slightly more loose than the other 4, must have been my error upon installing. Wonder if some seepage from the spark plug gaskets (that go on the valve cover, just replaced them) got down there or something like that? I wasn't too worried about it because like I said, the tip of the plug looked fine. I re-tightened the valve cover bolts so I think that should take care of that.