K&N Panel Air Filter - better performance?

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I realize this is an old thread but as it happens, I was discussing this very thing with my mechanic today. I've read about these filters on the forums and was curious. The people backing K&N claim a 3-4 MPG gain in normal driving, and a HP or two gain in more spirited driving. I was also intrigued by the "clean & re-use" aspect of these filters.
My mechanic (Wittler Auto here in Albuquerque) told me that in theory, these filters might be a good idea, but actually, they have a fairly serious drawback. The seal is made of a silicone material, and according to the Wittler, they've seen lots of these filters with deformed seals. Seems that the seals deform when they get hot, i.e. the silicone gets too soft. Thus, when the seal is deformed, unfiltered air gets through to the engine. Thus, they aren't too fond of these things. He did say that *if they were made better* they might be OK. But, they would cost a lot more, too. So, for the time being, I'm skipping them and staying with the standard OEM type filters in my 530.
Karl Winkler http://www.sandiastrings.com
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wrote:

deformed seals Huh! Are these on the filters that he has fitted I wonder?
More MPG - doubt it - never noticed it on my 740i E38 but then who would as the difference between 18MPG and 20MPG = heavy traffic or heavy right foot occasionally.
Might be cheaper in the long run - never ever bought a new air filter for the car in all the years I had it so must have saved 300 or $600(US).
But economy - never. Deformed seals - never. Sad filter seller - yes!
Sir Hugh of Bognor
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Karl Winkler wrote:

The problems with K&N go beyond the poor fit (and they do fit poorly..)
They also don't filter as well as the OEM paper filter - in numerous tests it's been shown they let more dirt through than the factory filter does. The oil on them also has a bad habit of migrating down the air-stream through your MAF (Mass-Air-Flow sensor) - and often is responsible for the failure of the MAF (which costs $200-500 depend on what engine you have and how many you have..) BMW will not warranty any MAF on an engine using an oiled filter. The filtering is worst when the filter is freshly cleaned and oiled, and gets progressively better over time as the filter starts plugging up.. until it gets so plugged up the dirt ends up being pulled through the coarse cloth mesh. They are not really a good thing for your engine.
The cost savings is actually also questionable. BMW makes a filter that tends to self-shed dirt it picks up. They typically last well beyond the recommended replacement interval with some simple removal, and tapping out of trapped dirt. On ones that are an updraft design - it isn't even necessary to perform that cleaning step - the design is such the dirt falls out of the filter into the airbox. For the cost of one K&N you can purchase at least 3 stock air filters from a discount vendor.
Performance gains also can't be reliably shown. BMW is awfully good at designing engines and designing them for maximum performance. There is no reason for them to go undersize on an airfilter since the cost per unit increase for an adequately sized one is negligible. They're not going to leave HP laying around on the table for some bozos cobbling crap together in a garage to pick up.
IMHO - K&N = marketing over performance.
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wrote:

I bought a K&N filter for my 1987 Toyota about 165000 miles ago and what I have noticed is it has shrunk somewhat, it still fits good and passes smog every time. the filter is 20 years old and is cleaned with every 3000 mile oil change. So that's 55 air filters @ 9 dollars a piece or a savings of about 495 dollars.
After reading all the opinions about the K&N air filters and my own experience and reviewing, the filter designs are somewhat flawed. I think K&N could have used better material that does not shrink over time. Advanced Flow Engineering Air Filters claims better material than what I have in my old, yet still good K&N air filter. I bought one for my 330CI and am hoping for the best.
Cheers,
Brian
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admin wrote:

Care to show one documented proof that they filter poorly?
I know, I';ve read it bazillions of times online too. I've just never seen good proof that this is the case. Perhaps it's people that don't know that you have to oil the filters?
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BIG Snip

There was a filter comparison done and posted on one of the bimmer boards. K&N passed more air (more horsepower?) and more of the smaller particles than OEM. I'd be leary of one in a dusty climate. I'd also be concerned about the possibility of filter oil accumulating on the MAF.
It's possible a well-designed intake system might give a 1-3 HP gain (and a poorly designed one, some loss), but I seriously doubt there would be any significant mileage improvement as claimed.
R / John
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wrote:

I was told years ago by a Formula Ford guru that oiled filters like K&N should not be cleaned and freshly oiled every five minutes. Something to do with a certain amount of crud actually improving the filtering capability without impacting airflow. 10K or 20K miles between cleanings, I was told.
But, most people who fit K&N want nice shiny chrome with the K&N logo plainly visible, and a nice clean pink filter. Not yucky-looking black ones like there were on my Caterham Seven that I sold 18 months ago and now seriously regret having done so - but that's another story.
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Fred W wrote:

Sure.. http://www.bobistheoilguy.com/airfilter/airtest3.htm
And you might want to read the entire article..
http://www.bobistheoilguy.com/airfilter/airtest1.htm

Well - now you HAVE seen it. This isn't the only test like this I've seen. There was another one with industrial equipment - where they did regular oil tests for silica (sand) - and matched it up to the filters being used. The K&N was simply awful - they went back to standard paper based filters.
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admin wrote:

Excellent!! That's just what I was looking for. Now I can continue to using the stock dry paper type filters for a good reason. ;-)
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Karl Winkler wrote:

The deformed seal argument is BS. Their seals are just as good or better than the OE filter seals. They do not deform when they get hot. Those guys are on crack.
The rest of the K&N "claims" is also BS. You will get no improvement in horsepower or mileage. You will get a filter that you have to clean and reinstall rather than just replace.
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Fred W wrote:

If so - so am I. I've had the K&N seal deform on a BMW motorcycle. The filter seal was too big, when the airbox was clamped closed the seal extruded from the seal area.

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