Macster

Good guess, but my guess is the layout has not that much to do with the smoking. I know it looks like it ought to but if it did then the smoking should happen every engine start.

My belief is the AOS is at fault, occasionally allowing a bit of too much oil laden vapor to pass through and into the intake manifold. As the engine runs this pulls in the oil constantly so you don't really see any signs of it burning. But shut off the engine and the oil that remains drains/rungs down and collects in one cylinder (if the intake valves are open) or collects on top of the intake valves of one cylinder (if the intake valves are closed) and upon engine start ... smoke.

Sincerely,

Macster.

Baggerdude

Mac ... that sounds like a more plausible answer than the others to me.

jhbrennan

Here's another opinion:

https://rennlist.com/forums/4021422-post8.html

Baggerdude

Sorta sounds like what I was saying ... altho my expanation was much simpler. I must be a savant.

Macster

But there are 6 cylinders and they are all flat and I have to point out the rod and piston and other in-cylinder hardware are thoroughly wet with oil spray from the piston cooling oil jet so there is plenty of oil to make its way past the rings and piston into the combustion chamber, so if this is the reason for the engine smoking upon startup why then do these engines not smoke every engine start?

Sincerely,

Macster.

jhbrennan

Don't know...but I do know I only get the white puff on startup if I start the car cold (after sitting overnight), shut it down after about 30 seconds and then start again in an hour - always smokes on that second start with that sequence. Wonder if the Suburu boxers experience this?

Bob in NY

If I move mine around the driveway and shut it off only after a few minutes of running I get the smoke on start up. I don't think it's a big deal...

Macster

It's not a big deal. Porsche techs tell me this smoking is quite common with new cars cause they sit around on the lot alot, get started infrequently and driven sometimes just a few feet.

The techs tell me absent any other signs of trouble and as long as the smoking is only at engine start, is brief and does not continue after startup or does not appear at any other time they don't worry about it.

If I treat my cars like you describe I sometimes see the smoking the next cold start. Otherwise, the smoking event is quite rare, sometimes I can start the car maybe 100 times or more (maybe a month or more worth of use) and not see any smoke.

Sincerely,

Macster.

Terry Adams

From the Subie board,

http://www.subaruforester.org/vbulle...startup-83085/

most think it is condensation, though a TSB (from the pdf) identifies some rare cases as oil related:

If you encounter a customer complaint concerning white smoke from the exhaust pipe and/ or high oil consumption, it may be the result of the # 1 and/or # 4 intake valve guide insertion hole improperly machined, permitting oil to enter the combustion chamber. To remedy this condition, the cylinder head(s) will need to be replaced. Please read this bulletin in its entirety before proceeding.

I like the Todd/A.W.E. explanation - oil.

Redmist

In the winter when I drive infrequently, it happens accasionally. This summer I've been driving it regularly and it has happened only a couple times and not as much smoke when it happens. Macster, what's AOS?

jhbrennan

Air oil separator - I don't think the GT1 engine has any because of true dry sump configuration.

Cowhorn

I thought I remeber being told on here years ago that white smoke was condensation and that blue smoke was oil being burned off.

Anyone else ever heard such?

Macster

Yes, though sometimes the color of the smoke is hard to determine. And there can be times when both water vapor/condensation and oil smoke are present.

White or very light colored vapor is water vapor. Normal of course from an engine being started under certain climatic conditions.

If the 'smoke' is water vapor it will dissipate very quickly. Oil smoke will linger/remain visible even as it is carried away by any breeze.

In some cases the water vapor can continue to be emitted even increase as the engine and its exhaust system heat up while oil smoke should be a brief event.

Sincerely,

Macster.