mglobe

This arguably should go in one of the water cooled forums, but I'm after answers from people who track their cars & (unlike me) know something about them too.

When I first start my car (997S) after a DE session, I generally get some smoke out of the exhaust. After a minute or two, the smoke disseapears, & the engine runs fine. If when come in, I run the car at a high idle for a minute or two (~2500 rpm), then let it idle normally for another 5-10 min, and then shut it down, the smoke is minimized. The car never smokes during regular daily driving, and is pretty fugile with oil usage (~1qt every 2000-2500 miles). I've talked to several people who all say "yeah, a lot of them do that & it's no big deal", I'm not sure if I should believe this to be true or not (the no big deal part). Comments?

mitch236

Actually, that occurs quite often. Maybe Agio will chime in with his tales of killing all mosquitoes in a 5 mile radius with his last 996!

Patrick E

Mitch, I'd like to hear that - I bought Agio's last 996!!!

mglobe

I'd love to hear an explanation for what exactly is happening to cause this. Is is blow-by during driving, or some sort of leakage during the cool-down cycle? If it is the latter, would running 5w40 instead of 0w40 help prevent it? Or should I just not worry?

smlporsche

It also happens with Boxsters and Caymans.
My understanding is when a "well exercised" flat 6 engine is shut off certain components cool faster than others and this allows a small amount of oil to seep past the rings.
Anybody confirm this?
I've been told that this is "no big deal" also from several people.

Patrick E

My indy and dealership both claim it's normal as well, but I can't tell you why. It does seem to draw some sympathetic looks at the track from people not familiar with these cars.

ervtx

mglobe,

As you know, this happens to me all the time. I tried the suggestion I recently received (running a bar or two low at the track - to reduce the vacuum pressure that amplifies the sloshing up to the seals). However, I didn't notice much improvement. For me, the single thing that reduces startup smoke the most is to let the engine cool down more slowly - 5 minutes seemed to be the threshold for me.

mitch236

Nobody seems to have the answer but one thing is for sure, alot of cars do it and it doesn't seem to affect performance.

Don't run your cars low on oil. These wet sump cars have enough issues with starvation to add low oil levels.

MacGT3

I had a very embarrasing issue with this for most of the 2006 season. The volume of smoke on starting the car after it sat between sessions was unbelieveable. I would actually engulf the car.

I found that my mechanic was over filling the oil when he changed the oil (after each HPDE).

The new mechanic put in the exact amount of oil reccomended in the manual and it has never happend since.

I know that some engine problems could cause this but mine was easy to fix.

My mechanic that was over filling the oil is a very respected member of an ALMS race team and he got it wrong.

I hope you can fix your problem as easily as I did.

TR6

Mike, I saw the smoke coming out of your garage at TWS this weekend, but I just figured that you and Steve were in there puffing cigars...

930man

no problem i typically run mine a 1/2 quart low ... but i keep an eye on it... slow easy cruise in from the track to the paddock helps... park on flat surface also helps ... but know big deal at all just an annoyance from front engine guys asking .... oh i think you blew something or your "rings are bad"....

TT Gasman

Mike it's common, but not normal IMO. Overfilling the crankcase with oil can cause this but I think oil pooling on one side or the other during high G runs is another possibilty. Maybe an early sign of oil starvation, maybe not. But what typically happens during high G turns oil pools in one head as it is not adequately scavenged. This is a function of the design of the crankcase M96/97, Porsche solves this on the Motorsports and X51 motors with an extra scavenging pump. At least that's what happened on the 996 motors. Did you happen to notice your oil pressure on turn1 this weekend? I remember my old 996 would bounce a little on that turn in that CW configuration.

sechsgang

i know with a TT engine, its more normal than NA...but I have given up on things that could be "wrong" with the pcar because so many things are *** backwards, I figure its generally doin' what it should...untill POP...haha...

Bob Rouleau

Smoke on start up is both common and normal. Various reasons have been given, most logical. Don't worry about it. Smoke at startup is common on flat and radial (airplane) engines. I like the rate of cooling theory myself coupled with the fact that oil can leak down past the rings. This is not limited to the wet sump engines, even 993 turbos do it from time to time.

eclou

Mike the reduced mass of your new wheels has led to excessive piston velocities in your car. You need to sell me those wheels immediately to remedy the situation