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exhaust soot - oil or fuel???

 
Old 02-13-2011, 01:29 AM
  #16  
Macster
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Originally Posted by mdrums View Post
So no...to exactly what?....the white exhaust tips means what...compared to the black sooty exhaust tips? Obviously there is a different burn, correct? You went off talking about fuel mileage of your Turbo.

I understand the soot not sticking to the exhaust tips at the track but then why do they turn white? I noticed that the GT3 Patron and Grand Am Porsche's all have this whiteish look inside the exhaust tips.

I'm no expert here but from asking around the garages at races and so forth I've been told that this is one way to see if the car's fuel burn is correct. Although I've heard a brownish rust color is prefered also but I heard about that in the V8 American car circles.
Sorry for the veer from the subject. Tired I guess.

The white tips mean nothing to a street car. To a race car the exhaust tip color can mean anything. Only the engine builder/tuner knows what or has a guess as to what it means. I'm sure he has plenty of other inputs as well to use to qualify the tip color.

(Also, one has to suspect some tuner giving away his 'trick' for reading the engine's combustion signs to his competitors. He might say 'white' is ok when in fact sooty is really want he wants to see.)

The fueling is correct when the engine's been given a 4-gas exhaust analysis and the analysis shows the mixture is right when the engine's makikng power where the tuner wants it to make power.

For street cars as long as the engine's running ok, the CEL is not on, flashing, the engine exhibits no untoward behavior, oil consumption is within the allowed range, fuel consumption is in expected range, and coolant is not disappearing into the engine, the exhaust tips could be plaid for all that it matters.

Reading the plugs is not an exact science even before all the goofy boutique gas blends so I fail to see how exhaust tips that are several feet from the combustion chamber and have the exposure to whatever the converters do to the exhaust gases can be any better a way to know anything about the engine's combustion.

Furthermore, no dealer service department is going to do anything about an engine that is exhibiting zero signs of trouble just on the basis of what exhaust tips look like, unless they're glowing red, dripping oil, coolant, or raw fuel or melted metal.

Sincerely,

Macster.
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Old 02-13-2011, 01:40 AM
  #17  
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I'll mention it in a separate post: I just covered over 240 miles today (from Hayward CA to San Luis Obispo) at freeway speeds (70/65 -- lots of bears!) in my Turbo and the engine managed to get around 25mpg and guess what? The exhaust tips are a bit sooty.

I'm saying soot happens and it means nothing.

Sincerely,

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Old 02-13-2011, 12:04 PM
  #18  
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thats exactly what happens to me Macster, Cruising- economy runs produce soot in the exhaust tips but great fuel economy without a hiccup from the engine..
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Old 02-13-2011, 01:23 PM
  #19  
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Last Thursday I was over photographing at Sebring during the 12hr test. Here are 2 photo's showing exhaust tips of cars that have been out all day testing.....note the white/gray inside the tips. All these type of cars looked like this.
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Old 02-13-2011, 01:34 PM
  #20  
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I mean this in the nicest way, but so?

Those cars are race cars with highly modified/tuned race engine sans any converters and the engnes are running on race gas.

The color difference between the exhaust tips of your stock street car and that of those cars means about much as the difference between the exhaust outlet of a bottle rocket compared to that of a Saturn V.

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Old 02-13-2011, 07:10 PM
  #21  
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Originally Posted by Macster View Post
I mean this in the nicest way, but so?

Those cars are race cars with highly modified/tuned race engine sans any converters and the engnes are running on race gas.

The color difference between the exhaust tips of your stock street car and that of those cars means about much as the difference between the exhaust outlet of a bottle rocket compared to that of a Saturn V.

Sincerely,

Macster.
Actually they run 93 octane...same gas as us....they are running Sunoco 93 at the track. I fuel up with Shell near my home which has up to 10% ethanol and drive to the track. I use almost 3/4 of a tank in the 1st run...tips are white...I re-fuel the rest of the day with the tracks Sunoco 93 no ethanol fuel....tips are white....I've used Sunoco 98 when they ran low on 93...tips where white. The engines in those cars are rather simular to the engines in our street cars....not like a bottle rocket vs. the Saturn V...that was funny though but a wrong anology.
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Old 02-15-2011, 01:10 PM
  #22  
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Soot is typically a fueling problem, over fueling to be exact, and has always been associated with diesels in the past. Soot winds up mostly in the engine oil, and diesel engine oils are formulated to be able to handle the increase in soot levels that today's diesel engines produce. It is of interest to note that diesels are direct injected engines as are the 2009 Porsche engines and some other German engine manufacturers. But with the computer controlling fuel delivery in the engines, how could soot creation be a problem in these gasoline engines?? I don't know the answer to that problem, but one guess I might have is that the computer is programmed to over fuel at lower speeds, or RPMs. This suggestion seems to have some validity based on the discussion here, that when tracked, or raced, the sooting condition is not found, and a white material is seem on the exhaust tips.

Just a theory on my part, but if you have soot on your exhaust tips and the back of your car, the next time you change your oil, see if it is extremely black, or blacker than you would expect. And note also, that automotive engine oils as compared to diesel engine oils, are not designed to carry heavy soot loading. If you do see a condition like this, you may want to consider a reduction in your oil drain intervals, even with Mobil 1.
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Old 02-15-2011, 01:56 PM
  #23  
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Originally Posted by Macster View Post

Those cars are race cars with highly modified/tuned race engine sans any converters and the engnes are running on race gas.

Macster.
Actually the race cars in the pics look like Patron Cup cars and most likely have cats installed.

The difference between a sooty black tail pipe on a street driven car and a white exhaust tip track driven car is exhaust temps. Temps will be 5-600 degrees hotter at WOT. Between the high temps and the high velocity, the exhaust is left clean of all carbon deposits.




Phil
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Old 02-15-2011, 05:25 PM
  #24  
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I ended up selling my 2009. Couldn't deal with adding a quart of oil every 400 miles. oh and the SOOOT... every drive, i was wiping down the rear bumper. It seemed to get worse int he summer. Alogn with the rear tail light always fogging up.

My car was on the cusp of being lemon lawed. In the end, Porsche said it was within spec. my 09 was a nice car, beautiful car to look at. But it shifted very roughly, its rear bumper was always full of soot, and she drank oil like an alcoholic craves a drink.

In the end, someone point out, in spite of all these issues, she hauled *** and drove really well. After the clunky shifting, oil compumption, i realized the porsche was never going to change. She was a high performance beast. And i could only enjoy that for only a short period of time.

my advice, since i fought city hall, is to just deal with it, or sell it. Porsche will never admit there is an issue, and sadly you got one of the bad, but tasty apples...
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Old 02-15-2011, 07:50 PM
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Originally Posted by RollingArt View Post
Actually the race cars in the pics look like Patron Cup cars and most likely have cats installed.

The difference between a sooty black tail pipe on a street driven car and a white exhaust tip track driven car is exhaust temps. Temps will be 5-600 degrees hotter at WOT. Between the high temps and the high velocity, the exhaust is left clean of all carbon deposits.




Phil
This is what I believe.
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Old 02-15-2011, 11:59 PM
  #26  
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Here is something to consider where sooting is concerned:

In order to achieve its higher performance potential at high loads, the DI gasoline engine should be operated under stoichiometric or slightly rich conditions. When charge is stratified, soot is generated in the rich zone, so sufficient excess of air should be provided around that zone in order to burn the soot generated. Therefore, when the average mixture strength is stoichiometric or slightly rich, that is, when the equivalence ratio is larger than unity, the mixture should be homogenous so as to supress formation of soot. With a DI system, homogenuous mixture can be obtained by an early injection.

In other words, at partial loads, the goal is to prepare a rich gaseous mixture around the spark plug and at high loads it is to prepare a homogenuos mixture. To achieve this goals, the combustion chamber geometry has to be optimized as a function of the given injection system and the in-cylinder air motion has to be controlled ,for example, by using variable valve actuation or port throttling. Furthermore, the exhaust aftertreatment has to be fully integrated in the engine system, even a new type of catalyst has to be developed that is able to work at lean conditions.

It is obvious that the whole engine concept is changed when introducing DI and the development of every system should be carried out along with that of the rest of the engine.

This was obtained from here...http://html.rincondelvago.com/direct...injection.html
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Old 02-16-2011, 02:11 AM
  #27  
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Thanks everyone for the reply's and so forth...thanks for this info Lubrecon.
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