I had removed the intake to replace the clutch on my alternator. Many folks over at the tdi forum go on and on about the clogging of the intake so I looked at mine. I had some crud so I removed it, scraped it, sprayed it with carb cleaner and pressure washed it. It looked pretty clean when done. No performance difference though. I guess it was not all that clogged. I was planning on installing a Mann Provent to reduce all that oil from getting in the intake. If any of you have removed the intake pipe you will see all the oil which may not be all that much but ti does accumulate over time. There are even articles that mention how to clean the intercooler of this oil mess.
My theory is that the oil from the crankcase vent mixes up with the egr gasses and the heat of the turbo to make some nasty coke or soot. Removing the oil from the mix should reduce that build up. I need to purchase a good vent to test my theory. Unfortunately it takes me about 3 years to accumulate 100,000 miles.
One myth proposed is that reving the engine will prevent these deposits. I generally drive for mileage getting 50 mpg regularly. Reving over 3,000 is rather rare and I generally shift at 2,000. I feel this is a myth because an engine is more often than not runnng at relatively steady states at relatively low rpms with relatively low boost. Second thought is that you have more crankcase pressure at higher revs. More pressure might mean more oil slung about that gets into the intake gunking stuff up. My third part of this is fluid dynamics. There are areas of high velocity and low velocity in an intake. You will get some deposits in areas of low velocity no matter how much you rev.
Some propose egr recalibration which apparently has drwawbacks like reduced power and reduced mileage. I believe I read that the computer makes some calibration related to the egr that reduces fuel flow.
Has anyone seen any good studies from a well educated mechanic or other source that might shed light on the oil-egr interaction?
Jim B.