Took manifold off...here's my thought on "carbon" buildup
12-23-2008, 03:48 PM
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Took manifold off...here's my thought on "carbon" buildup
<center><img src="http://i299.photobucket.com/albums/mm303/silverRS4/a-intakevalve.jpg"></center><p>A little over a month ago, had the car in for CEL, misfires, etc. They found bad injectors, replaced them and the car runs fine now. They also found the buildup on the intake valves that been talked about here. I was able to briefly look at it while they were cleaning them, but wasn't really able to inspect them. Well, I took the manifold off myself this weekend because I was bored and felt like wrenching on my car. It obvious from the intake ports and intake manifold that there is quite a bit of oil vapor in the intake air stream. Which is typical, especially on high performance engines. There is a light oily film on the manifold port (and flaps) leading directly into the cylinder head as well as in the port itself. The closer you get to the valves, the film is more tacky and in some places, almost hard. But not like dry flakes. IMO, the oil vapor entrained in the air stream just clings to the valves and sticks because the valves are relatively hot. Its not "carbon" buildup due to combustion, its oil film buildup thats not effectively cleaned by fuel since the engine is direct injected, not port injected. The RS4 has an elaborate crankcase ventilation system equipped with a 3-stage venturi cyclone to help remove the oil particles. Obviously it doesn't separate all the oil out. I don't think some buildup would be out of the ordinary on these engines. The valve in the pic was the worst and its been roughly 800 miles since the dealer cleaned them.
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12-23-2008, 07:50 PM
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Visual analysis done 800 miles ago, scratch Mobil 1
Didn't have to look too close when the dealer inspected the valves. After 3500 miles with Mobil 1, the crud was pretty thick. It took them 3 hrs to clean them all and airflow into the engine improved by 10%. Currently using the Castrol TXT 505 that Audi recommends for the direct injected engines. If I have to yank the manifold at every oil change I will - its not really a big deal.
