Dry/Wet compression results

[tay97gst]

So long story short, I bought my project car with no engine in it and bought a built engine off someone from the forums. I've finally installed every mod that I want to so it's time to get ready to get the car tuned and painted. It really only has idle time on it but it's been burning oil every since I got it running, (I know this because the smoke coming out of the exhaust and I have pics of the exhaust ports if you want to know the extent of how much oil its burning, spark plugs are also fouled). To find out what is causing it to burn oil I did a compression test today to see how the rings are.

The Results:For the dry test each cylinder was exactly 180, with throttle WOT, and for the wet each cylinder was exactly 210, with throttle WOT.

Just wondering if these results were enough to confirm that it's the piston rings and enough to warrant getting this fixed. Should I do a test to check the valve seals regardless, (a leak down test I believe)? I'll answer any more questions you guys need to know because I want to make sure the engine is absolutely running right before I take it to the dyno/track.

Spark plugs look like this on every cylinder

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Dry Results

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Wet Results (About half a cap full of oil)

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[1SloEvo]

Maybe I've been reading bad information, but there shouldn't be that big of a swing between dry and wet compression tests. When my stock motor had broken ring lands on all 4 cylinders, there was about 35-40 psi of difference in the dry test compared to the wet test, wet obviously being higher since the oil helps seal any open gaps between the rings and the cylinder walls. So I would definitely look into the rings!

 

[tay97gst]

Nope, you made me question myself for a moment though, When cylinder number 1 is at TDC Compression #4 will be at TDC Exhaust Stroke, In this picture below you'll see on that on when #1's lobes are facing up as they would be on compression stroke #4's are facing down as they would be on exhaust

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So I did some googling and found this "Keep in mind that you need to have it set at TDC of the intake stroke when testing. #4 will be at TDC of the exhaust stroke when #1 is set up properly and vice-versa. When at TDC of the exhaust stroke you will leak past both the intake and exhaust valves due to overlap." Which is what I think you were saying. So the way I set TDC only closes all the valves for cylinder 1? How do I make sure there closed to test cylinder 4 then?

Maybe I've been reading bad information, but there shouldn't be that big of a swing between dry and wet compression tests. When my stock motor had broken ring lands on all 4 cylinders, there was about 35-40 psi of difference in the dry test compared to the wet test, wet obviously being higher since the oil helps seal any open gaps between the rings and the cylinder walls. So I would definitely look into the rings!

I thought so too which is why I'm doing the leak down test, or trying to at least haha

 

[Dave4g63]

Well when I was going to school they told us anymore than a 5psi increase means bad rings, I have never actually followed that rule, considering your compression is 180 I would say your engine is fine, mines a mitsu rebuild and i only get about 160 across the board, my brothers 6 bolt is only 130psi across the board and both our cars run just fine. As for figuring out how to test number 4 just aline your cam gears with the dowel pins on the bottom.

 

[tay97gst]

Well when I was going to school they told us anymore than a 5psi increase means bad rings, I have never actually followed that rule, considering your compression is 180 I would say your engine is fine, mines a mitsu rebuild and i only get about 160 across the board, my brothers 6 bolt is only 130psi across the board and both our cars run just fine. As for figuring out how to test number 4 just aline your cam gears with the dowel pins on the bottom.

Alright thanks for your help, I'll try that tomorrow morning and report back.

 

[1SloEvo]

Well when I was going to school they told us anymore than a 5psi increase means bad rings, I have never actually followed that rule, considering your compression is 180 I would say your engine is fine, mines a mitsu rebuild and i only get about 160 across the board, my brothers 6 bolt is only 130psi across the board and both our cars run just fine. As for figuring out how to test number 4 just aline your cam gears with the dowel pins on the bottom.

Agreed that compression numbers can be very different and the engine still run different. But the difference between dry/wet test being that drastic on the same engine is what's throwing up a red flag to me. 180 is great compression. But a 30 psi difference is a LOT!

 

[Dave4g63]

A 30 psi jump is quite a bit But not something I would worry about unless the engine is high mileage, on my Bro's 6 bolt gst he gained 70 psi on cylinder 2 and 120 psi on cylinder 4 doing a wet and dry test, after the car got drove around a bit and everything was all broke in shes perfect now, holding 130 psi across the board

 

[1G Eclipse94928]

A 30 psi jump is quite a bit But not something I would worry about unless the engine is high mileage, on my Bro's 6 bolt gst he gained 70 psi on cylinder 2 and 120 psi on cylinder 4 doing a wet and dry test, after the car got drove around a bit and everything was all broke in shes perfect now, holding 130 psi across the board

130psi is almost out of service, sooo.....
Its okay but you know something is going bad.... OP sounds like you need to have the bottom end looked at.

 

[1SloEvo]

Or, if it's a new engine and only has isle time, the rings probably never seated properly. If this is the case, drive it with tons of varying revs and see if it gets better. If not, you must be beyond the initial seating period of the rings.

 

[dsmalaska]

Stock compression from factory as in, the perfect compression is 168, that being said the lowest(out of spec) is 114, your numbers are more than perfect so the 1st & 2nd rings are not an issue. check valve stem guides, make sure your oil ring on the piston is correct too, if installed backwards itll allow oil to flow by and not scrape it back down in the pan.

 

[tay97gst]

Alright so I went back out and tested it again what I believe is the right way. I tested the cylinders in order of 1-3-4-2, rotating the crank to make sure each cylinder was at TDC of the intake stroke (I think). The results are as follows.

Cylinder 1
Dowels at 12 o'clock, cam marks aligned
Air leaking out of oil/dipstick
PSI: 74/80 = 7.5%
*I retested this one again after I did them all making sure the cam gears were perfect and it came back at 79/80 = 1.25%

Cylinder 3
Dowels at 3 o'clock
Air leaking our oil fill/dipstick and little out of spark plug 2 hole
PSI: 78/80 = 2.5%

Cylinder 4
Dowels at 6 o'clock, cam marks aligned
Very little air leaking
PSI: 79/80 = 1.25%

Cylinder 2
Dowels at 9 o'clock
Very little air leaking out filler/dipstick
PSI: 79/80 = 1.25%

So I believe I was doing it right, but shouldn't a normal engine leak more than this even when it's healthy? I'm just not confident that I'm getting each cylinder exactly where it's supposed to be. What do you guys think?

 

[Dave4g63]

I don't see anything wrong with those results Yeah even healthy engines have a slight amount of leakage. What dsmalaska said about the oil rings being upside down sure could be true, you bought that engine you didn't build it yourself right? If you have air leaking from cylinder 3 into cylinder 2 that could be a bad head gasket but your leakage isn't high at all. If the cylinders weren't in the right place during testing you would see pretty much 100% leakage as you did before.

 

[tay97gst]

I don't see anything wrong with those results Yeah even healthy engines have a slight amount of leakage. What dsmalaska said about the oil rings being upside down sure could be true, you bought that engine you didn't build it yourself right? If you have air leaking from cylinder 3 into cylinder 2 that could be a bad head gasket but your leakage isn't high at all. If the cylinders weren't in the right place during testing you would see pretty much 100% leakage as you did before.

So does it sound like I did the test right this time? And yes I bought the engine used but the guy I bought it from used it for 7k miles with no problems like this, he made 500+ hp using the engine. I'm just confused how I'm getting oil into all 4 cylinders, compression is great, leak down is great, but it's smoking out the exhaust like a mofo.

 

[Dave4g63]

Are you sure all the smoke isn't left over from before you did the valve stems? I only know of a few things that would cause a DSM to burn oil, Rings, Turbocharger and valve stem seals. It's possible you have oil in the inlet track weather its Intercooler, piping, or even inside the intake manifold. Is the engines actual oil level dropping after you let the car run for a while?

 

[Gasolinebaptism]

I like how no one has asked you the compression ratio of your motor in order to know how much you should see on a compression test..
OP, you're getting oil from somewhere, the best advice is to go drive the car. Go drive it. For ten miles or so. Burning some oil won't hurt it.. Just let it get hot, burn oil that in the exhaust, get on boost and heat shit up. It's pretty tough to diagnose something based off of idle time.

 

[tay97gst]

Are you sure all the smoke isn't left over from before you did the valve stems? I only know of a few things that would cause a DSM to burn oil, Rings, Turbocharger and valve stem seals. It's possible you have oil in the inlet track weather its Intercooler, piping, or even inside the intake manifold. Is the engines actual oil level dropping after you let the car run for a while?

I'm pretty certain because of the amount it's smoking. I changed the spark plugs right before I delivered it to the guy who changed the valve seals and when I pulled them yesterday they were wet with oil still.

I like how no one has asked you the compression ratio of your motor in order to know how much you should see on a compression test..
OP, you're getting oil from somewhere, the best advice is to go drive the car. Go drive it. For ten miles or so. Burning some oil won't hurt it.. Just let it get hot, burn oil that in the exhaust, get on boost and heat shit up. It's pretty tough to diagnose something based off of idle time.

CR is 9:1, I have driven it, not just idled. I think I've driven it for 30 miles so far. The smoke is not very noticeable when driving but is noticeable when boosting it and is noticeable in lower gears. At least that's when I can see it best. And of course it's smoking at idle and shoots out a nice puff when I rev in neutral. I just think it's too much smoke for it to be burning off as well as coating the spark plugs with oil.

I would love to think it's the turbo but I don't see how oil from the turbo can get to the spark plugs since the intercooler piping is clean. The only thing I can imagine is that the oil is like flowing from the turbo through the exhaust ports and getting through the valves when they open, but I don't think that can realistically happen?

 

[Gasolinebaptism]

Look inside of the intake manifold. Let us know how much is in there. Money says it's not dry.

Or the intake tube, see if there's a puddle under the compressor wheel.
I know it's a rebuilt turbo, but people make mistakes.

 

[boost97gst]

Less than 2% leakdown??? Wow. That is unreal.
Very healthy to say the least

 

[tay97gst]

Look inside of the intake manifold. Let us know how much is in there. Money says it's not dry.

Or the intake tube, see if there's a puddle under the compressor wheel.
I know it's a rebuilt turbo, but people make mistakes.

Can i just remove the throttle body and look inside with a flashlight or does it have to come off? What would this indicate?

Less than 2% leakdown??? Wow. That is unreal.
Very healthy to say the least

My thoughts exactly which is why im so skeptical haha

 

[boost97gst]

I would be too. You know, personally being such a dummy, when i checked mine i actually took the valve cover off and put a long screwdriver down the well to make 100% sure it was tdc and i could visually see that all valves are closed. I used a different tester(harbor freight) and i think the regulator on it was set at 30 psi or so. But the results would level out pretty quickly and the gauge would read appropriately.

First off, what tester are you using? I was just surpised to see 1: so low of numbers and 2: so specific. i.e "1.25%" etc.. It seems you allowed a certain amount of time and then noted the drop in psi and calculated leakdown from that. That may be viable but if you dont have one, a true leakdown tester will put your mind at ease and give you results accurately and repeatedly. I think they loan them at some auto parts stores. If not the harbor freight one is about $30 iirc.

 

[tay97gst]

I would be too. You know, personally being such a dummy, when i checked mine i actually took the valve cover off and put a long screwdriver down the well to make 100% sure it was tdc and i could visually see that all valves are closed. I used a different tester(harbor freight) and i think the regulator on it was set at 30 psi or so. But the results would level out pretty quickly and the gauge would read appropriately.

First off, what tester are you using? I was just surpised to see 1: so low of numbers and 2: so specific. i.e "1.25%" etc.. It seems you allowed a certain amount of time and then noted the drop in psi and calculated leakdown from that. That may be viable but if you dont have one, a true leakdown tester will put your mind at ease and give you results accurately and repeatedly. I think they loan them at some auto parts stores. If not the harbor freight one is about $30 iirc.

Its an otc leak down tester so its a pretty good quality piece. Instead of the second gauge reading the actual percentage of leakage this tester shows you how much psi the cylinder is holding in relation to the amount of pressure being put in. I calculated the percentage afterward. You can see how it works in the video i posted.

 

[boost97gst]

My bad, missed that. Watched the video and im not familiar with the tester but it sure as hell looks like you're doing everything right.......smh, damn dsm's. This is a good one. Tricky problem you got. Hope some more people weigh in.

You did check your intake pipes right? Are they oily or dry?

 

[donniekak]

Hours of nothing but idle time on a new engine can make it burn oil. What are the afrs it's been run at?

 

[Gasolinebaptism]

You can just push open the throttle body and look in with a flashlight.

 

[boost97gst]

He said a page back that it hasnt been only idled, he drove it ~30 miles as well. Thats plenty of time to seat the rings if done right

 

[tay97gst]

He said a page back that it hasnt been only idled, he drove it ~30 miles as well. Thats plenty of time to seat the rings if done right

Yeah ive personally put 30 miles on the engine the previous owner put 7k so this problem isnt from the rings not being broken in. I'll take apart the intake and intercooler piping next chance i get but last time i checked it was very clean. I'll report back with what i find.