Compression Test
 

I recently did a compression test on my car, I came up with the numbers 110 all around. Which is odd because normally when there's piston or valve wear it isn't even like that all the way around. My question is, will the results differ between doing the compression test dry or wet (putting a few drops of oil into the cylinder before the test), I did mine dry so maybe if I do the oil thing I will get better results. Also, I know that we had discussed that the compression numbers should be between 160-180, would the numbers differ on a turbo model if those numbers are for an N/A model??

the oil doesnt fix anything. all the drops of oil to is get up agenst ur cylinder walls and seal the rings better

Oh, I was told that the numbers would probably be higher if I added some drops of oil into the cylinder before I did the compression test. Can you confirm what the numbers are supposed to be for a turbo model? And if my numbers are correct and they are that low, did I just get "lucky" or something that all the rings or valves wore out in unison like that?

This really needs to be answered as gilber33 and myself have experienced this. I did the oil test and jumped from 120 up to 180.

OH REALLY!?!? Well then I will definitely try adding the oil to it this weekend before the meet. If I have good compression then there must be something else causing my blow by.

Adding oil to the cylinders determines if the rings are worn or not. If the numbers go up a significant amount, the rings are worn. If they stay the same or just go up a little, something else is wrong, like a head gasket or something with the valves/heads.

oh, is that what it is? I guess that makes sense. I'm going to assume that it's my rings then because I still have blow by even after redoing my PCV system.

Welcome to my boat. I am looking into re-ringing my block. Unless someone can clarify the low compression. I saw a significant jump in compression when adding a few drops of oil. I can only asume my rings are shot.

by the way...I noticed the new addition to your signature...funny.

haha, thanks, I assume then that I will find the same thing if I did that to mine. I was thinking about new rings as well, but when you do that, can you just replace rings and that's it? Or do you have to do more than that? I assume you would have to do a head gasket kit like the ones that IPD sells.

what droping the oil in does is temporary coats the walls of the cylinder makeing a tight seal if you dont have one already. and it wont burn off during the test because there is no spark/power stroke. once you go through spark and power stroke all that oil burns. if oil in the cylinder helps your compression, your rings are bad.

It's gotta be the rings since I still have blow by. I guess I'll see what happens this weekend when I add the oil and do the test again. I just don't know if only added rings in my car is worth it since it has so many miles. It would probably benefit from a rebuild, but that's a lot of money to throw at it.

If you decide to do the rings then you may want to replace the rod and crank bearings too. Just good sense. The bottom end, I believe, only has crank seals to replace and a few O-rings. No gaskets other than chemical and waterpump. Head on the other hand has a few. I picked up my engine stand and cherry picker Saturday so mine will be coming out shortly. I also found a 3"turbo housing at the wrecker and in the process of pulling together a reversed intercooler. I want low 14's at the track when I am done.

Yeah, I don't think I want to spend that much money on this car. I am saving right now to eventually get an 850R or V70, so I think for now I'm just going to deal with the shotty compression.

Just did test on my 94 / 850 turbo & got 150 psi to 152 psi So 110 psi seems low. The psi gauge should jump right up to 100 then higher on just a couple of seconds. If it comes up slower you probably have valve or ring issues. Oil drops in cylinders only confims worn pistons if the pressure comes up but the drops off.

My engine ran smooth just burned blue smoke. Turned out to be worn turbo blowing oil back thru intake manifold. If turbo has 140 k or above it should be rebuilt. lots cheaper than cylinder head removal / replacement or ring job.

False. My turbo has 214,000 miles on it and has no shaft play, I know because I took it out last month to exchange housings on it. These turbos can last forever if they're not abused. And rebuilding my turbo wouldn't fix the fact that I have low compression, I would have to replace rings either way.

Yeah, mine slowly climbed to 110, did it in three jumps, from 75 to 90 and then to 110 where it stayed.

gilber33,

Did you swap out your turbo housing for the big one? I just found one at the wrecker and bought it but did not know if it would work. It fits on the turbo and everything I have read says its interchangeable. I went back for the down pipe but someone took it the next day...sucks. Can you tell me more? Fit, performance, noise...details please.

I swapped my conical housing that was on my 15G with a straight housing because my DP only had options for straight and angled housings. It was only in 94 and 95 that Volvo used the conical housings, in 96 all of them were straight housings. Compared to the straight and angled housings, the conical housing is extremely restrictive. The straight and angled housing are larger with a larger exhaust outlet that connects to the down pipe, allowing for more flow. The housings are a direct fit, all you have to do is take off your turbo and there a band that hold the housing to the rest of the turbo, it just slides off and you slide the other housing on.

Matched with an aftermarket dp you should notice faster spool up times and the wastegate opening and closing is more prominent, sounds like a mini BOV. While the turbo is out, it's a great time to inspect your turbo, make sure it's still in decent shape. When putting it all back together, you will need new copper crush washers for the oil and coolant lines.

Unfortunately i dont know what 'conical' means. I know my 15g exhaust leaving the turbo exits horizontally to the passenger side of the car. The new flange I picked up the exhaust exits the same but is pointed down some and it a larger diameter.