Blue smoke during accel

[turbski]

Getting some blue smoke under load. Ie hard throttle or free revving above 3k. Never smokes on cold starts or just cruising. Want some advice on troubleshooting and if its something I should even look to deep into. . . any advice always welcomed.
Thanks

[MrBurgundy]

Seems like you're burning oil.

There's a number of reasons it will do that, but one place to start is doing a compression test. You might have worn rings.

[Das Delfin]

Mine did this, a bit of smoke only on hard accel from a dead stop, and I thought I had worn rings but a compression test showed that the motor was within spec. My car uses a surprisingly small amount of oil as well at 240k mi but then again I use 15w50 synthetic so a more "normal" lighter oil would burn more. I read somewhere on a bmw forum that revving your car up burns off loose carbon deposits on the tops of the cylinders and is actually healthy for the motor. The idea is the more often the motor is exercised like this, the less smoke you'll see. BMW even says in the owners manual to run the car at 3k+ rpm for 10 mins or so (ie on the highway) to burn off condensation inside the crankcase. Do a compression test to make sure but it worked for me and I hardly see smoke in my mirror anymore.

[Q5Quint]

If it smokes free revving AND under boost it might just be too much oil in the turbo. Cold oil will be higher pressure but less flow, so you would usually expect it to smoke when it was cold if this was the issue. What size oil fittings are you using? Mine smoked awfully with a 4an and just about stopped completely except at cold startup with a 3an.

[turbski]

I get next to nothing for smoke at cold starts, once in a while it will puff a little out then stop completely. it only seems to do this under boost. or free revving.
I will say though that the car does not drive everyday. it was noticed after a few days of sitting and then a cruze through town, I let it eat with a friend behind me, they asked about the smoke? I then parked the car for another 3-4 days took it out to wash it, backed into the garage and wanted to hear the motor and noticed a small cloud of blue smoke.


compression test has all cylinders sitting around 140-150, I asked the guy I bought it from (also a member here) what his results were and they were the same.


As for the AN lines, im unsure. I will double check and post.

[Jaxx_]

this is probably RPM/oil pressure dependent. Do you have an oil pressure gauge?

How big is your oil drain? Do you have a ball bearing or journal bearing turbo? I advise against running a restrictor or smaller oil feed line before investigating the drain.

[turbski]

Yes to the oil pressure gauge, journal bearing turbo, the oil return line looks to be 5/8 O.D and the feed line is pretty small. maybe 1/4 inch I.D.

[citizen_insane]

Yes to the oil pressure gauge, journal bearing turbo, the oil return line looks to be 5/8 O.D and the feed line is pretty small. maybe 1/4 inch I.D.

5/8 OD? That's way too small. That sounds like a 6AN equivalent tube when most applications should run 10 or 12 AN. You want your drain line ID to be at least as large as the opening in the bearing housing so there's no restriction of oil in the line. You also want to minimize bends. Ideally, you would have less than 90° of total bending in the entire line, although that's often impossible.

[turbski]

still seeing the blue smoke but not completely sure how or what I want to tackle first. Seems like it does it when letting off the throttle after making a pull or revving it up? have seen very little oil consumption but im not putting a lot of miles on it either. Gonna post a picture of oil feed line and return line and see what the thoughts are.

[e30davie]

Seems like it does it when letting off the throttle after making a pull or revving it up?

Based on this comment, Id be looking at valve stem seals.

When you jump off the throttle you go from high pressure in the cylinder to high vacuum, sucks all the oil past the valve stem seals if they are a bit worn.

[turbski]

any quick checks that could be performed that could prove or dis prove

[citizen_insane]

any quick checks that could be performed that could prove or dis prove

What turbo are you running? Post pictures of your oil drain setup.

[e30davie]

any quick checks that could be performed that could prove or dis prove

If they are really bad snapping the throttle closed even on free reving should produce a plume of blue smoke out the exhaust.

[Q5Quint]

Common perception is that if the turbo oil drain is not free flowing enough then oil gets backed up in the turbo seals and it will smoke. If it is just when the engine revs (and increases speed of oil pump) you may be getting a blob of oil stuck at the turbo for just that moment before it can drain away again?

Maybe start the car and see if it is smoking like this, then disconnect the drain and let is shoot into a bucket and see if it stops. Edit: that would at least rule out the drain itself, but technically the seals could still just leak at higher rpm or something.

[turbski]

that would be doable. Im not losing a noticeable amount of oil, I just try to make things run as they should. I have had limited time with getting ready for winter so apologies for not providing pictures yet. but its on my list of things to do.


It does produce a pretty decent plume of blue smoke if I bring it up over 3k and snap the throttle closed. but I will def try trouble shooting it during its end of year oil change before it goes up for the winter.


should be able to post back in the next couple days with some updated pics and an update