Black deposits on exhaust (update)

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newbiecrg

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I think some of you noticed black deposits build up in the exhaust... well I recall than being mentioned anuway. Mine did got those deposits as well (I noticed that all the time when cleaning the car)

What do you think is the cause?

I know is not oil consumption...

Today I brought my car to London and after 2200km (yes I did it in one go I am mad...) and about 250 of petrol there are no deposits at all... Two things might be the cause either petrol is of better quality in Spain and France or a proper motorway cruise cleans it up... Not that I used it in town before... but I just wanted to share this... perhaps someone has a proper explanation...

Pedro

P.S.: No speed tickets and an average speed of 80mph (in 2200Km I behaved... ahaha)
 
nothing important maybe a bit of residues if you don't give it a good blast ... That is what i think it is
 
If the burning of oil is excluded the other two possibilities that cause soot are lots of cold/cool running or too rich a fuel/air mixture. The former appears to be the likely one.
 
Yes... that is my opinion anyway. Burning of oil is excluded as there isn't any abnormal oil comsumption on my S3. Has 12k miles now and not even half a litre was used to top up... so pretty good!

Pedro
 
I get loads of this crap on mine, I thought it was just pollution from the engine...
 
Probably the best check of all of an engine's health is to remove and examine the spark plugs. They will tell you a lot about your engine's combustion process.
 
yeah you are right... I have some background on that from my go kart days... But like i said in this long trip i didn't got any deposits so I am going to wait and see...

Pedro
 
I think it's just short drives that cause it. I know my car runs very rich on start up. Economy is shocking on short runs!!!!
Nothing a bit of meguirs NXT metal polish can't shift!!!
 
mine was exactly the same and I asked a specialist about it (Statller) who said it was normal as the TFSi runs fairly rich on one of its cycles. The car did not use excessive amounts of oil only requiring 1 top up in 6,000 then I had a 12 month extra oil change by choice.

My 2.0TT also gets the black deposits on the exhaust tips but wipe away easily, again no oil useage so far.
 
newbiecrg said:
or a proper motorway cruise cleans it up...
Click to expand...

I believe that's your answer

I live in central london so do loads of stop start motoring - I've had it on all my cars; petrol, diesel, N/A & turbo variants

IIRC it's hot unburnt fuel collecting soot deposits from the exhaust and getting burnt/stuck on the tips

high speed driving burns fuel more efficiently than sitting in traffic (less unburnt fuel) plus the air flow around the exhaust together with the high speed of gases exiting from the exhaust reduces the fuel settling on the tip

HTH
 
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