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D3 A8/S8 (2004 - 2010)
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I know how to oil them and...
Posted by: MP4.2+6.0 (4369) on 2009-07-23 20:55:18
In Reply to: A majority of the people who screwed up their MAF put too much oil on the filters. posted by Push That Tush on 2009-07-23 15:58:57

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I tested it across two MAF's on a 4.2 C5, where one was new and one had been used with a K&N for maybe 30K miles. Cost 10%+ on measured peak airflow for what the MAF saw, which translates to HP LOSS. The telltale red oil dye down the intake tract was the give away--it was a very light mist film to be clear accumulated over several tens of thousands of miles, not oil run off type stuff. Virtually ANY oil on the MAF filament wire and it's toast as far as accuracy. I have tried both spray and bottle type application, and putting it on very light and still letting any excess run down/off overnight or longer. And, cleaning with rubbing alcohol or electro type cleaners doesn't bring it all the way back either.

They did work okay seemingly on a 2.8 C4 and on a pre MAF C3 with CIS-E, but definitely bad news on a C5 4.2, using actual measured airflow calcs with VAG COM in a back to back swap out of the MAF and all other parts constant.

Factoring in the MAF damage risk and expensive part (and it's often insidious since it affects airflow just marginally, not catasprophically), going to a 15K air filter change, or even just blowing it clean at each oild change, is more cost effective and risk free. The good German filters also often have more pleats if you get technical about flow capability, and if you really look at the car hard, you may conclude the air inlet to the filter box is the bottleneck; it pretty much is obvious on the C5 anyway, where the then 4.2 S6 variant used a stock box and filter but an air bypass valve and different manifold (unclear if cam was any hotter from the specs). The known changes suggest where the real flow problems are on the 4.2, at least on the pre FSI ones. If you have the round type filter on the D3, I would say even less likely it is the bottleneck since they went to that relative to the older panel ones to up the flow (and capture area) yet somewhat more.
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