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      07-01-2010, 08:28 AM   #6
Lance Corporal

Drives: 08 335i, Graphite
Join Date: Nov 2007
Location: Maryland

iTrader: (1)

Originally Posted by Ilma View Post
This is well intentioned, but also a shining example of how incorrect information keeps getting regurgitated by inaccurate and untested explanations.

I am sure everyone has seen the pictures of our intercoolers and intake pipes that are completely covered in oil residue from crankcase blowby.

There is far more oil contamination in the intake system from your own engine than there is from an oiled air filter.

Have a look here for some actual measurable testing on this:
ALL of the the engine contamination is post MAF sensor in any car. I'm not aware of any OEM (not saying it doesn't exist but I'm not aware of any) that mounts the MAF sensor after the PCV return, turbo, vacuum hoses or any other engine connected tube. Virtually all OEM MAFs are located near the air filter and pre-boost. There is no engine oil contamination on the portion of the intake before the PCV return hoses or turbo.

Thats's why when folks do custom blow thru MAF setups (after turbo) on built turbo cars (for when you want to retain the MAF low end drivability without the intake restriction) it is highly recommended that a catch can or air oil separator be used in order to prevent oil contamination of the MAF.

Also, while I have experienced oil contamination post filter with K&N setups you're also comparing the K&N to an oiled foam filter. Last foam filter I used, on a rotated turbo setup on an STI, was very heavily oiled and I saw visible oil residue in the MAF tube which was right after the filter.

On a side note, I don't think K&N's own testing on this subject should be considered the most unbiased. I have run several K&Ns in the past (Vette, WRX, STi) and have definitely had to clean the MAF sensor due to receiving MAF related error codes.

I'm not saying it was a big deal. Contamination really didn't start to become a problem on the K&Ns (actually two K&Ns and one Injen filter) until over 10k miles or more of use after new or re-oiling. And it was very easy to clean, just remove the MAF, spray down generously with MAF or electronics cleaner, clean the housing and exposed areas (not hot wires or MAF components) with a q-tip and be on your way.