Compression test number - Good or not?

Don't know which ones are 1,2,3 and 4 so here are my numbers by location.

Driver rear - 126 - 127

Driver front - 130

Passenger rear - 137

Passenger front - 130

This was done on a cold engine.

I did some research on the board here and it seems that my numbers are ok for a cold motor.

I am burning oil...and am in the process of determining how much oil for a given set of miles. 105,000 on original turbo so it could be oil seal in turbo. I wanted to get opinions on my compression numbers.

Happy Halloween! :icon_chee

Do the tests on a warm engine. That will tell you if there is a real problem.

On a cold engine that has been running for a while normal wear will cause some leaks but they will close up when the engine gets warm. And as long as you don't have any considerable oil consumption you should be good.

Usually when you do a compression test you should look out for a single cylinder with unusually low compression. That's an indication of something not sealing right. But that has to be done on a warm engine.

Do the tests on a warm engine. That will tell you if there is a real problem.

 

On a cold engine that has been running for a while normal wear will cause some leaks but they will close up when the engine gets warm. And as long as you don't have any considerable oil consumption you should be good.

 

Usually when you do a compression test you should look out for a single cylinder with unusually low compression. That's an indication of something not sealing right. But that has to be done on a warm engine.

^ what he said, you are also doing a dry compression test, while i do not see any problems with your results, if it will make you feel better you can also do a wet compression test, where you apply a *small* amount of oil into the spark plug hole and perform another compression test and check your results. i however do not think this is necessary, how much oil are you burning?

It's already been mentioned a couple of times, but do the compression test on a warm engine, and hold the throttle open while cranking (not actually sure how this works with DBW, maybe someone can chime in on this?). Also, pull the fuse for your fuel pump so you aren't injecting fuel while cranking. You are looking for the numbers to be within 10% of each other, don't pay so much attention to what the actual number is as there are many factors that can affect the readings:

-the gauge used

-how many times you crank the engine over

-atmospheric pressure where you do your test

-etc

For these reasons, you can't directly compare your results to what someone else got, and make any conclusions.

If you feel you are burning oil, do the "wet test" after the dry test, put a cap of oil down each cylinder and repeat the test. If your numbers come up a bunch, you can determine you have worn rings, if they stay the same, you would suspect valve seals as the culprit.

Atmospheric pressure have a very small impact since the compression meter isn't measuring absolute but relative to current air pressure. The precision of the meter is usually off a lot more than the atmospheric pressure can do anyway.

But I agree on the wet/dry test.

Atmospheric pressure have a very small impact since the compression meter isn't measuring absolute but relative to current air pressure. The precision of the meter is usually off a lot more than the atmospheric pressure can do anyway.

 

But I agree on the wet/dry test.

That was just an example of one of the many factors that can affect compression test results, and why you can't directly compare them with someone else's results, but you're right, it will account for only a small variance compared to some other factors.

Sorry to sort of threadjack but is 110 an good number if its on all cylnders along w/ 5% leakdown. I had mine tested at a local tuner and they said I was good but I've seen websites claiming that 130-150 is a good number.

I also saw ehsnils post about relative pressure and atmospheric pressure but I couldn't tell if that applies in Denver as well since the relative pressure is about 18% less than at sea level.

110 seems low to me based upon the research I've done on the board. I had one cylinder at 126-127 and thought that was a little on the low side but I was told that since I did the test with a cold engine that it was acceptable.

I'm no expert by any means so hopefully other will chime in.

Have a great day!

IMO If the #'s are within the 5-10lbs your fine. Don't worry about the actural #. Most of these engines use oil. If the engine runs good, has good power, then drive it. Keep checking the oil every few day's to get a idea of how much it's using. Keep toping off the oil as needed. Mine has been been using oil for years, I have not worried about compression numbers. The engine runs fine, I went stage 2, two month's ago.

Drive the thing. Stop trying to fine things wrong just so you can spend money on it.

Just keep a eye on the oil level and top it off everytime you check it. I check mine every 3-4 day's.

And be aware that the precision of the compression testers that you get in the shops have a precision that is very crude. If you want to get it right you should get one with a certified calibration.

So for the cheap testers - if the compression is equal on all cylinders be happy enough. This since it's extremely rare that all cylinders fails in an identical manner.

Only case I can think of that may cause a compression to be symmetrically off is if the timing belt is off one or more tooth on the crankshaft. But that would at the same time also cause other kinds of trouble.

IMO If the #'s are within the 5-10lbs your fine. Don't worry about the actural #. Most of these engines use oil. If the engine runs good, has good power, then drive it. Keep checking the oil every few day's to get a idea of how much it's using. Keep toping off the oil as needed. Mine has been been using oil for years, I have not worried about compression numbers. The engine runs fine, I went stage 2, two month's ago.

 

Drive the thing. Stop trying to fine things wrong just so you can spend money on it.

 

Just keep a eye on the oil level and top it off everytime you check it. I check mine every 3-4 day's.

Well said, I feel like way too many people on here think there car is about to blow up. It's gonna use oil, just keep checking it.

That's about three to four quarts per tank. Way too much.

It's like filling oil and checking the gas.

I would say that if you have to fill oil more often than every fourth tank or so you should consider checking what the problem is. (rule of thumb, not a definite statement)

My wifes impreza will use about 1-1.5 quarts after 3-4k miles and thats a 141k mile EJ253 motor. Mine will use about 1/2 to 1quart after a 3k interval and I have 105k on my engine now. Still stock turbo.

Both have never had the PCV valve changed which I think is the culprit for 90% of the oil consumption.

I can replace her's easily... Mine is in that damn plastic housing that I'm afraid to crack while trying to remove it so I need to be careful when attempting it.

Sorry you're right every 1000 miles not 100 miles:eek:. I have 105,000 on my motor and am still on the stock turbo.

Lowest (cold) compression test number was 126-127. Two of them were 130 and the other was 137.

Do you think the turbo is the culprit in burning the oil or is it the PCV?

How can I find out?

Well the only way to my knowledge to check the turbo would be to remove the down pipe and see if there is any oil accumulation around or on the exhaust turbine.

And for the PCV just take it apart and see if the line going to the engine is soaked with oil residue, granted there will be some, but also check to see if the valve still moves freely. It may be all gummed up. I know cleaning the one on my wife's car brought the consumption down but it's starting to go back up, so I need just replace it.

Leakdown test will give you much better indication of a cracked ringland...

This. If you hear teapot whistling when you apply pressure, you know something is up

Where is the PCV on the LGT?

Under the TMIC center somewhat passenger side behind the intake... Remove the IC and you can see all the lines for it. Its not the easiest thing to find, and its threaded into a black T like intersection... IIRC Subaru sells the entire part including the plastic to replace it, but you can also buy just the valve for a EJ253 motor and replace that if you can get it to unthread without breaking the housing.

FBP also sells the setup for a 05-06 LGT. 07+ is different once again, but this image gives you an idea of what your looking for. The PCV is the part facing directly back with the hose on it.

http://www.fredbeansparts.com/media/catalog/product/cache/1/image/5e06319eda06f020e43594a9c230972d/1/0/10105ab790.jpg

Thats ^ $30 bux from FBP btw... so not bad to just replace the whole setup.

OP, there is a artical in Saturdays local paper in the automotive section about oil consumsion. Seems like some of the manufactures think a quart ever 1000 miles is ok.

Just keep an eye on it and top it off as needed. Like I said I have been doing this since about 75,000 miles. I'm at 135,+ now. Still on the oem engine and turbo.

FWIW, I have been 1300 miles since the last oil change 13 days ago. The first 800 miles I use no oil. Did a 400 mile drive last Saturday, used about 1/3 of a qt.

I went stage 2 in early Sept, oil consumsion hasn't changed. I checked the DP, no oil residue, I've had the tmic off a few times in the past months. No oil in there worth worring about either.

I also have a air/oil seperator installed.

I also have one step colder plugs.

Engine runs fine.