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WEASEL149 · Joined: 19 Aug 2005 Posts: 595 Location: UK, Sheffield

OK, we all know they increase air flow but is the filtration they offer as good as the original filter (or better) at removing the crap from the air?

I'm just concerned about Turbo compressor blade wear, if the air going through it contains more crap.
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1979 UK 932

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

They they filter better than most OEM filters, but the OEM german paper filters are really good compared to most older american/japanese filters. I was reading on one page where an E30 BMW OEM Mahle air filter outflowed the K&N drop in replacement.

A K&N will filter more than well enough, I wouldn't worry about that too much. I have one in my car, and my brother had one in his 931 for many years, neither of us have had any problems. The fitment is a bit shoddy for the NA, so it needed a bead of silicone to make the filter housing secure and tight.

My brother's 931 was an interesting case, he looked around a bit for filters, and the K&N filter was only about $10 more than an OEM, and it'd never have to be replaced, so it was a pretty sound fiscal decision.
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'81 931 in various states of assembly

AGD931 · Joined: 17 Mar 2003 Posts: 289 Location: Athens, Greece

I read somewhere that as the air passes over the K&N it takes with it the lubricating oil on the filter and it then flows through the intake.

The last car I used a K&N was 99 Focus, and when I changed the throttle body for something bigger in 2001, there were oil deposits in the intake. As for the "performance" gain, sorry but I just could not tell the difference.

I use the original Porsche filter in mine, I agree that financially the K&N makes more sense.

In 911&Porsche world recently, one of the specialists stated that on the dyno, a drop in K&N filter on a Boxster S, showed no measurable increase in power.

Arthur
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1981 931 S2
1990 E30 320i Cabrio
1979 Ford Capri Ghia

Paul · Posted: Mon Sep 05, 2005 3:39 am Post subject:

K&N air filiters are a waste of money in our cars. How many of us even change the paper filter every year? I'll bet even less will take the time to remove, clean, and re oil the K&N. A dry K&N will allow dirt into your motor that even a dirty paper element would have caught.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

CBass · Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada

I agree with Paul for the most part, but the 931 air filter can be quite expensive, and faced with owning a car for a considerable length of time, the cost of replacing it a few times makes it worth the cleaning and oiling of the K&N.

The only reason I have a K&N in my car is that it came with a parts car, and my old filter was welll past due for replacement. It'll do until I replace it with a cone air filter as part of an EFI conversion.
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'81 931 in various states of assembly

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

If you decide to go with a K&N do yourself a favor and NEVER clean it! They do NOT filter as well as paper until they are good and dirty. When K&N first started marketing their product it actually said this right on the box they came in! I like K&N filters but like most things there is no free lunch.

Oh, and never use one on a car with a hotwire or resistor style MAF. The oil and dirt will foul them in no time.

Todd