3" true dual with no H or crossover so at least in my case it does

 

I pulled all the plugs and #5 was soaked in oil (cylinder side) and the rest were basically new looking. So does this mean it's most likely the oil control ring? As I mentioned, compression and leakdown are good on all cylinders!

 

^While I'm sorry you're experiencing a problem, I'm super pumped that it's similar to mine, so hopefully we can help each other out.
To me, this is now screaming valve stem seals. My theory is that if your oil control ring was buggered, I still think that the top two rings would effectively scrape off any excess oil and you wouldn't be having the visible smoke. The fact that your leakdown and comp tests were strong, you know that your compression rings are good and that's great.
That JohnWigs guy is the man when it comes to the seal replacement.
I have the parts for mine, but I still haven't taken the repair on. The crazy thing with mine is that it has practically stopped... I'm not sure what that might be telling me, but time will tell.
Please keep this updated.

 

one method to determine oil control ring vs. intake stem seal leaking could be to :

a) pull intake plenum, upper an lower.
b) with a camera scope you should be able to visually see oil contamination on the "top side" of the intake valve and stem in the expected cylinder.


this at least should help isolate the oil source.

 

Good idea... I'm adding that to the queue .

Today I filled the #5 cylinder to the rim with MMO (mystery oil). After a few days I'll pump out whatevers left and see if anything's improved over the next week. Although it isn't a sure fix even for the oil ring, I'm starting with the basics as my time and budget are very limited.

But with the amount of OC coming from a single cylinder with normal compression I'm really starting to think it IS the intake valve seals.

Is it typical for just one valve seal to go out in such a drastic fashion?

 

Since I've essentially ruled out the turbos, mods could you move this back one level into the engine/drivetrain section?

 

from ReSmarted's quote:

... if it is a RevUp then it is a sure bet the rings are toast...

I'm trying to figure out an oil smoking issue of my own.

what about the valves of a RevUp would make the above statement true?

Thanks

 

For what it's worth, I solved some of the smoke issues by soaking #3 with mystery oil for several days. Increased compression on the cylinder as well (160 on #3 vs 150-155 on the rest). The remaining OC I have is a combination of turbo seals and just plain leaking.

 

^That's weird. How could that fix any sort of problem at all?

 

It's supposed to free up the oil control ring so it spins/moves freely.

 

Also clears up carbon build up. Thinking about doing it on all cylinders now after seeing the compression increase!

 

did you notice the compression increase immediately after soaking the cylinder, or did you run the engine? A wet cylinder will always so higher compression, so you would want to test it after going for a drive to see if it really went up.

regarding a couple of your older posts in this thread, i have seen engines with broken top ring lands compression and leakdown test just fine. but i have never personally heard of a VQ with a damaged piston... seems like everyone looses a rod or bearing first?

leaky valve guides will burn the most on cold start because oil in the cylinder head drips and accumulates in the intake ports / cylinder. when the engine is actually running, its burning it as it drips so it doesnt build up to generate as much smoke.

With your high mileage, you might play with the PCV system. Extra blowby from ring/hone wear with your mileage could cause higher crankcase pressure, which only makes the turbo drain issues worse, causing oil to burn out the turbine, and also increasing PCV in general (not sure if you have a separator or stock PCV layout).

My Greddy TT 370z only likes to have the oil filled to the bottom level of dipstick. If I fill it up to the top line, it will burn off to the bottom line within a week, then stay there forever. That last quart/inch of oil pisses off my turbos. GTR's have a secondary stage on the oil pump that actually pulls return oil out of the turbos... so its not anything I find strange to see VQ with side mount turbos having drainage issues or being very sensitive to crankcase pressure.

 

^thanks for the info. To answer your question, I had put about 200 hard boosting miles on the engine before checking the compression again after the soak. So there was no 'soaking' effect, the number really did increase. I'll do the same on the rest of the cylinders later.

I stuck a scope down each spark plug hole and didn't see any cracks or damage on the cylinders. The walls weren't scuffed or scored either. Just a -ton- of carbon build up on the cylinder heads.

As for cold startups, there's no smoke at all. So I doubt the valve seals are the issue. Only when the engine is fully warmed up do I start to get a puff out the exhaust when hitting the gas after an in-gear decel.

Interesting about the oil level... I'll let it run down to the low mark and see what happens.