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rage385
04-07-2015, 07:34 PM
Hey everyone,

I did a compression test on my 1.8t and got the following numbers:

Cylinder 1: 180
Cylinder 2: 150
Cylinder 3: 165
Cylinder 4: 175

After doing some reading, I know that the lowest number is good, but I also know that the variation is an issue. I guess what I am asking is, what do you guys think? Do I have anything to worry about?

Thank you

MrSnickelsnizer
04-07-2015, 08:20 PM
Honestly, probably not. I bet you are fine. Anything more than I believe 10psi difference should be looked at closer though... 1st thing 1st though. Since you did a compression test that's great. Next I would do the couple drops of oil in the weak cylinder to see if that brings up the compression. Then you know if you have ring issues. If it doesn't then I would take it to a shop that could perform a leak down test to see if the valves were slightly off and not sealing in the head. I would tell you to just look in there and check for deep scratches on the walls 1st, but just like a leak down test not everyone has those tools (slight scratches are just fine fyi). Best of luck.

rage385
04-07-2015, 08:31 PM
Thank you!!!!

M-Hood
04-08-2015, 08:11 AM
Any variation is bad, this means the ECU is working harder to balance it all out. You really need to do a leak down test to find out where your losing the pressure, my guess will be rings seeing these cars are pretty old and need ring replacement sooner or later.

The stock compression of a AWM should be 185, to give you a comparison that 150psi is slightly lower then 8.5:1 CR.

Corrado_Guy
04-09-2015, 06:48 PM
Was the engine hot or cold? For accurate results the motor should be hot.

rage385
04-10-2015, 08:54 AM
The car was at operating temperatures

redline380
04-10-2015, 10:25 AM
I forget what the allowable limit is in variation, but you are within it (20 or 30%). Also, you would have to test more times and take the averages. One test is not enough and certain factors could give wrong readings

Corrado_Guy
04-11-2015, 08:01 AM
I wouldn't be worried with those numbers as such but I would be concerned with cylinder 2 and a bit less with cylinder 3. I believe the variance is 40 psi between cylinders is okay so you are well within the limits but there is certainly something up there. My next step would be to do a wet compression test to see if the numbers come up at all (rings) and then to do a leak down test. This will give you a much better idea of how things are going and what to look at next. With those two low cylinders you will not get as much of a punch out of those cylinders which can also throw things off a bit. Also, because you are getting close to the limit it is not going to take long to go beyond it which is why it would be good to figure out the issue now. Are you having oil consumption issues or anything? Don't forget, you crank the motor over until you reach the highest number and not turn each over 5 times or something like that.

M-Hood
04-13-2015, 04:17 PM
I forget what the allowable limit is in variation, but you are within it (20 or 30%). Also, you would have to test more times and take the averages. One test is not enough and certain factors could give wrong readings

It is 10% from the highest number, but that is just so the dealership has something to fall back on when they deny there is anything wrong. What is the point of having a motor that is less then perfect?