Exhaust smoke on startup after DE sessions -- 996's & 997's
02-12-2008, 06:29 PM
#16
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I agree with Bob. Every Porsche I have ever owned, on occasion puffed a good ball of smoke on start up. Not every time, on its own time. My Boxster TT and now the GT3. Its a Porsche thing. Dealers tell you its common. I have heard the explanation but I could not recite it.
02-12-2008, 07:16 PM
#17
The Penguin King
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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.
You guys are always so helpful.
02-12-2008, 08:31 PM
#18
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Great recommendation, however. Wish I had taken notice. I sometimes change the angle of my camera to focus different parts of the car, including the tach, so I'm going to go back and see if I can make out the oil pressure readings from some of my video...
02-12-2008, 09:40 PM
#19
Burning Brakes
Mike,
I have an 80 SC and a 03 Boxster. The SC (with 115k miles) used to puff smoke on start up at random times and it seemed to me that it did it more in the mornings when it had been sitting for a while than at the track. I rebuilt the engine during winter of 07 and it has not smoked since. The Boxster with 37k miles does it as often as the SC used to. I would guess once every 10 - 20 starts. Everyone I have spoken to says it is Porsche genetics.
If you are really worried, do a leak-down test.
I have an 80 SC and a 03 Boxster. The SC (with 115k miles) used to puff smoke on start up at random times and it seemed to me that it did it more in the mornings when it had been sitting for a while than at the track. I rebuilt the engine during winter of 07 and it has not smoked since. The Boxster with 37k miles does it as often as the SC used to. I would guess once every 10 - 20 starts. Everyone I have spoken to says it is Porsche genetics.
If you are really worried, do a leak-down test.
02-13-2008, 12:20 AM
#20
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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.
02-13-2008, 01:48 AM
#21
Rennlist Member
I have done nearly all mods possible (X51 oil pan with baffles, 3rd radiator, 1/2 quart less oil, etc) to avoid this issue and occasionally after a session on track it would still happen. My latest approach (and successful so far) has been to idle the car for 5-10 minutes after exiting the track before shutting down. There are many explanations on several boards including pca.org as to why this happens. In any case, my temp solution seems to avoid the embarassing smoke out following a track session.
If anyone has a better explanation AND solution, please bring it on!
If anyone has a better explanation AND solution, please bring it on!
Last edited by smsarchitects; 02-13-2008 at 01:49 AM. Reason: more info
02-13-2008, 02:04 AM
#22
Drifting
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Sadly, the only cure is the motorsports oiling kit, also found on the x51. I remember riding with Hurley at PDE and the oil pressure was bouncing around like it was attached to a bungee cord! He said it was normal...
I had the exact experience as you in my old 996 on that turn. But it never smoked so go figure Conversely my turbo stayed pegged at 5 bar thru the entire turn .
At this level of driving it's good practice to take a quick scan of your gauges on straights and long sweepers imo.
I had the exact experience as you in my old 996 on that turn. But it never smoked so go figure Conversely my turbo stayed pegged at 5 bar thru the entire turn .
At this level of driving it's good practice to take a quick scan of your gauges on straights and long sweepers imo.
Last edited by TT Gasman; 02-13-2008 at 12:06 PM.
02-13-2008, 02:03 PM
#23
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Smokey Engines
The smoke ,we watercooled Porsche have to put up with is from the crankcase breather system. It is not able to seperate the oil and air before venting into the intake manifold. The Cayman ,I race has a larger breather system on it and NO smoke ever, regardless of how hard its raced. I am working on a smaller crankcase breather, 3-4 months before its released. Need to test. This will be the 4th version, so We done a lot of testing.
02-13-2008, 07:48 PM
#25
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The smoke ,we watercooled Porsche have to put up with is from the crankcase breather system. It is not able to seperate the oil and air before venting into the intake manifold. The Cayman ,I race has a larger breather system on it and NO smoke ever, regardless of how hard its raced. I am working on a smaller crankcase breather, 3-4 months before its released. Need to test. This will be the 4th version, so We done a lot of testing.
I thought that you were selling the Cayman? Still planning on racing it this year?
02-13-2008, 11:39 PM
#26
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The smoke ,we watercooled Porsche have to put up with is from the crankcase breather system. It is not able to seperate the oil and air before venting into the intake manifold. The Cayman ,I race has a larger breather system on it and NO smoke ever, regardless of how hard its raced. I am working on a smaller crankcase breather, 3-4 months before its released. Need to test. This will be the 4th version, so We done a lot of testing.
02-13-2008, 11:48 PM
#27
The Penguin King
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I've had it vary from a puff of smoke, to as you describe churning out smoke for a minute or two, worse on one side than the other. Assuming the breather system fixes it, is this something that really needs to be fixed, or is it (the smoke) just an annoyance?
02-14-2008, 02:07 PM
#30
Race Car
Mike,
While I don't have a solution I just wanted to chime in to tell you my 3.4l 996 does this too. I have started to let the car run for a few minutes after each track session to lessen the effect on the next startup but for the most part I just ignore it.
Andy
While I don't have a solution I just wanted to chime in to tell you my 3.4l 996 does this too. I have started to let the car run for a few minutes after each track session to lessen the effect on the next startup but for the most part I just ignore it.
Andy