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1G Burning oil in boost, help me troubleshoot

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Anthony Boni

5+ Year Contributor
213
23
May 13, 2018
Wrightstown, New_Jersey
As the title states, I’m burning oil in boost. I can see blue smoke behind me when I get into higher boost (25+ From a FP Red). Then when I let off, the smoke goes away. If I start accelerating again, there’s a bunch of blue/white smoke for about 5 seconds.

I compression and leakdowns tested today, here are the results-

1 cylinder: 9% leakdown, 190PSI compression
2 cylinder: 8% leakdown, 195PSI compression
3 cylinder: 6% leakdown, 200PSI compression
4 cylinder: 8% leakdown, 195 PSI compression

I also pulled off my FP intake pipe from my turbo. There was literally one drop of oil, but no real evidence of oil in the compressor side. It looks very clean.

I removed my LICP to see if there was any oil, and it’s very hard to tell. I don’t really see much of anything inside of the pipe. Just a slight film on the walls. But no oil pooling as I would have expected with how much oil is being burnt.

The bottom end seems very healthy. High compression numbers (9.3:1 motor) and low leakdown percentage. I don’t suspect high blow by, even though I have a .050” PTW clearance with a .026” top ring gap. I have an excessively efficient crankcase ventilation system because I built the motor a little loose for higher boost applications. The turbo is being fed from the OFH (BSD) with a restrictor. The drain is a 10AN from extreme PSI (perhaps the drain needs to be larger?).

No smoke at idle or while cruising, only when I go into boost. I’m suspecting the turbo, but I have nothing to back that up. Zero in and out shaft play. Slight side to side. MAYBE oil is getting past the turbine and burning in the exhaust, but I’m not sure how to prove that.

Maybe it’s coming from the head? Bad valve guides? Valve seals typically leak and burn oil at idle and start up. But stranger things have happened..

Any help would be awesome. Thanks!
 

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Have you measured crank case pressure/vacuum under all driving situations? I see you have what seems to be a large, vented can't with two larger lines running to it, but do you have anything actually pulling vacuum on the crank case?

Also not sure how much relief those lines can do in that particular spot, but it located slot of the ventilation responsibilities in one specific area.

Just some observations, but I would recommend adding something to actively pull pressure from the crank case, especially under boost with your looser bottom end specs, especially when you're getting good compression and leakdown tests.

Could also pull the O2 housing off and see if the turbine is all oil slogged, but I kinda don't think you'll find that. The drain could be bigger, but I don't see that being the issue either as you're only have issues in boost.
 
The factory outlet on a T25 is 1/2in equivalent to 8AN hose (I just checked my old turbo to make sure) so if I had to guess I would say its that 5/8 or 10AN hose as you have suspected. If the oil can not drain fast enough pressure starts to build up in the cartridge where it will try to squeeze through every little nook it has access to. I personally would run a hose at least the same size as the diameter of the oil drain port on the turbo maybe even a bit bigger. Avoid sharp bends in the hose and keep it above where it is emptying into the oil pan. If at all possible make sure that its not emptying below the oil level in the oil pan. This will make sure it drains adequately through the hose.
 
Have you measured crank case pressure/vacuum under all driving situations? I see you have what seems to be a large, vented can't with two larger lines running to it, but do you have anything actually pulling vacuum on the crank case?

Also not sure how much relief those lines can do in that particular spot, but it located slot of the ventilation responsibilities in one specific area.

Just some observations, but I would recommend adding something to actively pull pressure from the crank case, especially under boost with your looser bottom end specs, especially when you're getting good compression and leakdown tests.

Could also pull the O2 housing off and see if the turbine is all oil slogged, but I kinda don't think you'll find that. The drain could be bigger, but I don't see that being the issue either as you're only have issues in boost.
My old catch can had a vacuum source pre-turbo actively pulling vacuum on the crankcase. I have measure crank case pressure with both a VTA and a sealed catch can. The difference was nearly negligible between both set ups, and I was measuring from the balance shaft hole. The most vacuum I datalogged with the sealed set up was -.6 in/hg (if I recall correctly). With my VTA set up, crankcase pressure does not exceed .2PSI at full boost (34PSI). I went to a vented set up because that slight vacuum wasn’t worth pulling oil into my intake stream. I have two 10AN from the oil cap only right now. I’m going a little overkill and I’ll have two 6AN from the stock locations on the valve cover, as well as a 6AN from the oil dipstick using STM’s vented dipstick. But as far as I can tell, crankcase pressure is in check.


The factory outlet on a T25 is 1/2in equivalent to 8AN hose (I just checked my old turbo to make sure) so if I had to guess I would say its that 5/8 or 10AN hose as you have suspected. If the oil can not drain fast enough pressure starts to build up in the cartridge where it will try to squeeze through every little nook it has access to. I personally would run a hose at least the same size as the diameter of the oil drain port on the turbo maybe even a bit bigger. Avoid sharp bends in the hose and keep it above where it is emptying into the oil pan. If at all possible make sure that its not emptying below the oil level in the oil pan. This will make sure it drains adequately through the hose.

I can try and snag a picture of the turbo drain, it’s just a 10AN rubber return hose that bolts to the factory turbo drain return on the oil pan (well above the oil level). I could try to run the stock 2G drain, but I kinked two of them. That’s why I inevitably went to the 10AN drain!
 
The difference was nearly negligible between both set ups, and I was measuring from the balance shaft hole. The most vacuum I datalogged with the sealed set up was -.6 in/hg (if I recall correctly). With my VTA set up, crankcase pressure does not exceed .2PSI at full boost (34PSI).
FYI-This difference would be significant to me.
 
Liquid oil in the elbow off the turbo compressor housing or burnt oil/nastiness on the hot side/around the turbine heatshield could be places to look
When in boost or can you take it to higher RPMs while still in vac and not burn oil? Looking for oil pressure being a factor there.
 
FYI-This difference would be significant to me.
The MOST vacuum I saw was -.6 in/hg. On average I saw -3in/hg. .2 PSI is the most pressure I’ve seen with my vented set up. Usually, I’m right at 0/.1 PSI.

With the sealed set up, I was sucking oil vapor into my intake. Oil has an octane rating of 0. I’d much prefer a small amount of crankcase pressure over having extra vacuum in the crankcase that I realistically don’t need.


Liquid oil in the elbow off the turbo compressor housing or burnt oil/nastiness on the hot side/around the turbine heatshield could be places to look
When in boost or can you take it to higher RPMs while still in vac and not burn oil? Looking for oil pressure being a factor there.
I can take off the LICP and put my boost duty to 0% in link. My oil pressure sensor took a dump, so I can’t see what my pressure is at WOT. That could be an issue though.
 
This is with the lower intercooler pipe taken off and revving to about 5500RPM. Compression and leakdowns are golden. So it’s either the turbo drain, too much oil pressure as @curt-s stated, or the turbo hot side seals going bad?

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I think Thunder is on to part of the problem there. Oil doesn't weigh much and considering that the drain port of the turbo is only a few inches above the drain inlet on the oil pan there isn't much gravity can do to make it flow. Any bit of crank case pressure could impede flow. If the oil builds up even a little in the line it will create a "seal" allowing even the slightest bit of crankcase pressure to hold oil in the line thus causing it to back up into the turbo. Imagine steam hammer but with much less pressure. Fluid dynamics are kind of unfair like that sometimes. Did you port the turbo drain inlet hole on the oil pan? If I'm not mistaking it is only 1/2in from the factory. That could cause a small amount of oil to pool up in the bottom of the return line parallel to the ground and effectively reduce the available area inside the hose for oil to drain through. There is also the matter of the diameter of the drain hose itself. Perhaps a 12AN would make a bit of difference? From what I have read FP generally stands behind their turbos only needing a restrictor in certain situation and since you are using one I don't think that's an issue but I may be wrong. These are all very small issues and in some cases irrelevant but in your case perhaps the combination of them is causing a larger problem. I know you don't want to use the factory PCV design but that may help. I have heard of people using turbo drain pumps but that seems a bit excessive in this case.
 
@Anthony Boni
If it's leaking from the turbine side ring, you may be able to see some wet spot between the heat shield and the center cartridge if you remove the turbine housing. (I see some kind of wet looking spot in the pic you upload in the post #5, but can't judge by the pic)
Or didn't you blow the engine or the turbo before this build? If so, perhaps old oil from the previous build still remain somewhere between after turbo and the muffler. (I had this case before)
Anyways you should distinguish if the leakage is from pre or post turbo first.
 
Took off the turbo and inspected the hot side, no oil. Then I removed the exhaust manifold and found some oil on #2 through #3’s valve stems. Not a lot, but there’s oil present.

Compression and leakdowns good
Turbo is good. No oil in turbine or compressor.

I’m suspecting the cylinder head. Bad valve guides, or stem seals.
I talked with @DSMPT for a while, he gave me some sound advice that I’m going to try prior to yoinking off the cylinder head. I’ll update here as I figure more out. Thanks again everyone for the help.
 

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I’m going to be pulling the head off soon. I’m still second guessing it being the cylinder head. I’m hoping it is, because the only thing left would be the rings. But considering my leakdown and compression numbers are very good, I don’t think it could be the rings. If my oil control rings were failing, wouldn’t I burn oil all the time? Not only at higher RPM, but at idle and during normal acceleration? Tomorrow when I pull off the intake manifold in preparation to remove the cylinder head, I will be looking inside the intake side of the cylinder head in hopes of seeing oil. If I don’t see any oil, I’m going to remove the Head and the oil pan. I’ll then remove each piston/rod to see if I can find anything wrong with the rings and signs of improper installation.

EDIT: F*ck it I’m pulling the motor tomorrow. I don’t feel like doing all this crap with the motor in the car, so she’s going on the engine stand for diagnosis.
 
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I think Thunder is on to part of the problem there. Oil doesn't weigh much and considering that the drain port of the turbo is only a few inches above the drain inlet on the oil pan there isn't much gravity can do to make it flow. Any bit of crank case pressure could impede flow. If the oil builds up even a little in the line it will create a "seal" allowing even the slightest bit of crankcase pressure to hold oil in the line thus causing it to back up into the turbo. Imagine steam hammer but with much less pressure. Fluid dynamics are kind of unfair like that sometimes. Did you port the turbo drain inlet hole on the oil pan? If I'm not mistaking it is only 1/2in from the factory. That could cause a small amount of oil to pool up in the bottom of the return line parallel to the ground and effectively reduce the available area inside the hose for oil to drain through. There is also the matter of the diameter of the drain hose itself. Perhaps a 12AN would make a bit of difference? From what I have read FP generally stands behind their turbos only needing a restrictor in certain situation and since you are using one I don't think that's an issue but I may be wrong. These are all very small issues and in some cases irrelevant but in your case perhaps the combination of them is causing a larger problem. I know you don't want to use the factory PCV design but that may help. I have heard of people using turbo drain pumps but that seems a bit excessive in this case.
I may try a 12AN return just for peace of mind, but the turbo return doesn’t seem to be the problem here. I say this because there was zero oil in my intercooler piping, and no oil on my turbine hot side.
 
Pulled the motor. Removed the cylinder head. Removed all the valves. 99% sure it’s coming from the valve guides/seals on #2. Im sending the head off to get new guides, seals, and resurfacing completed. I’ll update this post once I have everything back together! Should be just a few weeks.
 

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It’s a sad day. I pulled my pistons out after seeing some markings on the cylinder wall. I believe this to be the problem with my oil consumption. I built this engine trusting my machinist to get my piston to wall clearance correct. I was wrong for that. Because I’m pretty sure he f*cked it up. With a cold .020” over piston on a cold block, both sides of the skirts are lightly contacting the cylinder walls on each side. I’m bringing the block and my pistons to a machinist I trust on Monday. He’s going to measure the bores and my pistons and let me know what my PTW clearance is. It’s going to be close to nothing though, I already know it. I’m hoping he can hone it to the correct clearance without having to get some new pistons.

I am still sending the head off to get some work done. The block is already decked and line honed, all it needs is a hone (hopefully not a bore) and she’ll be back on the road. No big deal. It was nice to inspect my bearings and my oil pump and see everything else that I did was performing as expected. Just very disappointing to see the one thing I entrusted in somebody else was done improperly. Oh well. This time, I check over the machinist’s work!
 

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I was going to say, I have never seen exhaust valve guides leak that bad. Dude, I'm sorry to hear all that though. After having found one so useful in the past I didn't even think of using a borescope to look at the cylinder walls which probably would have helped in the first place. I bought one a year or two back for that same reason and haven't touched it since. I forgot about it completely until now.
 
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