Martin Nedom

Why does a 911 engine typically produce exhaust smoke when the cold engine is started and during early running?

wolfgang1

Borrowed from dr google

It’s the nature of the Porsche flat 6 engine that oil can seep into or past the rings when the engine has been sitting some time. It should clear up in a few minutes of running.

theiceman

Also it can seep by the valve guides in 3.2 engines of which this is a known issue. Nothing serious to worry about.

TDS911

Because the engine cylinders are horizontal, instead of oriented up and down, there is always a little oil that stays on the lower cylinder walls after shut down, instead of gravity dripping back down into a sump like a vertical oriented cylinder. When the engine cools down and tolerances loosen (metal shrinks when it cools) that little bit of oil can seep past the piston rings into the combustion chamber and burn off when fired back up.

All my modern water cooled 911 Turbos even did this, due to same engine configuration. It isn’t just an air cooled thing, fwiw.

FA18C

What everyone said above - also, when the engine cools it condenses air into water that also burns off when you start. So some of the smoke is oil, some water... Car will tell you if you have issues with oil. If you are using more than a quart every 800-1000 miles you are likely just fine. If you are crop dusting the neighborhood, well, you get the picture.

theiceman

only thing worse than overfilling your oil ..... being the guy in the targa with no roof following the guy who overfilled his oil ...

FA-18C

Behind my Targa that does not have a CAT - welcome back to the 70s