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Black Carbon with water droplets

CVN187Y

CVN187Y

New member
I have a 924S, and the engine is in good condition. The oil bar is at approx 2bars at idle, the water temperature never rises above half on temperature gauge, there is no oil mixed in with the water coolant, oil looks like clear honey, oil filler cap has no water droplets inside the cap and there is no leaks on the all the oil seals including the oil/water intercooler which has just been changed recently. The car hardly uses any oil or coolant.

But at the end of the exhuast there is heavy carbon which is probably down to unleaded fuel. When the car is running black bits of carbon spit out with droplets of water. Does anyone know what this is? Or is it a pre-warning for something expensive about to happen?
 
hi is the porsche fitted with a cat ?.it just sound's like it's running a little rich and blowing carbon out of the exhaust.or it could be to many short runs on choke.may need a good run out..cheers carl
 
My car does this when first started from cold and it does run slightly rich when hot and on boost, leaving a slightly sooty tailpipe.
 
condensation in the exhaust mixing with the carbon soot. Especially bad at this time of year and the exhaust can store a lot of moisture.
 
Yes, the rear of my car over time gets peppered with black spots which come off when I eventually get to wash the car.
 
Phew!. Cheers guys.

It does a very short journey to work when it is raining, other than that I cycle to work. It does have a cat converter and I have just taken it on an 80mph 200 mile run and all seems to be ok. Perhaps I was worrying a little. No water droplets at all[:D] and no oil has been used.

Thanks.[:)]
 
These cars do run rich. I think because the AFM is a pretty rudimentary device and not too accurate at all the chips are programmed rich to be safe so the result is alot of carbon in the exhaust.
 
What oil grade are you running? The reason that I as is that 30-odd PSI at idle is a little low and this is usually caused by running a relatively thin oil. In theory all oils are the same viscosity at a set temperature, but in practice 5w synthetics tend to cost about one atmosphere of pressure at tickover. Im currently running a fully synthetic Silkolene 5w-40, which is superb, but completely unsuitable (it came from a sponsor so I cant complain). When it comes time to change I will probably opt for Castrol GTX High Mileage and shorten the service intervals to 3,000-6,000 miles, depending on use. This is a mineral 15w-40 oil and it is far better suited in a 2.500cc car.


Simon
 
mmmm, the old oil debate again!! There are so many variables to consider. I have been using Silkolene 5w40 for about three years now and my oil pressure gauge sits rock steady at around 3.5 bar at idle and 5 bar under load, which is perfectly normal. Also i'm not using a drop. So I don't believe that the oil viscosity (within the Porsche recommended range) affects oil pressure. Obviously if you stick something in that is out of range then you might see some issues.

On the contrary - fully synthetics are much more able to retain their viscosity over use. A mineral oil or semi-synth will break down much more quickly than a fully synth. That is the main benefit of a fully synth.

Anyhow, i'm pretty sure the symptoms that the black spot syndrome is carbon from un-burned fuel being spat out of the exhaust and not oil.
 
I always use Mobil One S oil 10/40 grade and change the oil and oil filter every 6000 miles or 6 months depending what comes first.
 
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