K&N

[cnavarro]

The '99 I just bought had a MAF failure at only 35,000 miles (Sept '08) - car has had a K&N in it from the start. It was cleaned and re-oiled at 30,000 last year at 30,000, per the dealer notes. The first thing I'm doing is putting in a fresh paper filter. From the many used oil analyses I've done on various customer cars, I've found that silicon levels (dirt, contamination) are about double for engines running a K&N filter. The only cleanable air filter I have seen that doesn't allow more contaminants in are the oiled foam filters - there are a few out there. For reference, here's just one comparo of foam versus k&n:

http://www.smartsynthetics.com/articles/amsoil_vs_kn_two_stage_air_filter.htm

Sorry to post an Amsoil link, but it's the first one I found in Google.

The best foam air filters are those made by ITG:

http://www.itgairfilters.com/

Another good link to read up on air filter testing is:

http://www.bobistheoilguy.com/airfilter/airtest1.htm

K&N does offer foam pre-filters for some filter types, which would bring their performance up to par with other filters. But just changing your paper filter more often will yield roughly the same performance (at a greater cost of course over the lifetime of the car if you don't count MAF failures with over-oiled K&Ns).

[mikefocke]

and because it doesn't have lawsuits against the company that makes the product is no reason to assume the product is any good. The purchasing may be due to marketing (and K&N has done a lot of it over the years). And the lack of lawsuits may be due as much to the difficulty of proving the cause and damage as for any other reason. Damage from the increased abrasion would occur over many years. How would the lawyer prove how much of the wear was the portion caused by the dirty oil that was caused by the difference in filtration?

The comparison test I saw was in a magazine about 2-3 years ago. Amsol's tests came up with the same results.

Charles' oil samples testing only confirms what these other two tests have shown...the K&N when properly oiled lets in more particles of dirt and bigger particles of dirt.

If you want to install one because you think it sounds "cool" to have one...it is your car, your money and your choice. Or if you value a few HP over increased wear, then that is a valid argument for you. Or if you use the car on the track and your class allows the change, that too can be justified by the tests.

But don't kid yourself that it is the best air filtration device you can fit to the car to filter dirt from the air and keep it out of the engine.

If you have one, change your oil much more frequently (which will cancel out and advertised reuse savings in using the K&N).

There are some additional test results in this link

[edevlin]

I am not advocating one type of air filter over another, I just thought I would share one Boxster owners experience with a cone-type filter element, mine is part of a TTP intake. I had it installed a couple of years ago, before I knew much about the discussion about possible clogging of MAF sensors and oiled, paper filters possibily doing a poor job of filtering. I just knew it sounded great, as most of the aftermarket intakes do.

I have used my oiled TTP filter element for about 35k with no problems with the MAF what so ever. I clean and oil the filter element pretty often, because it gets dirty so quickly. I probably clean and oil it every 5-7K on average. Over the period of use the cone-air-filter, I have sent my regular 5 to 7K engine oil change samples in for analysis. They have come back saying the oil was very clean, and on one of the analysis sheets, they said whatever kind of air filter I was using, it was doing a very good job.

I am pretty careful when I oil the filter element. I usually blow some air through it after I have oiled it and lightly rub a rag over the surface. I dont know how different the cone-filter I use is, but it is sourced from BMC I believe. These filters are are not cheap, I think I paid 160.00 for an extra filter element. One more data point.....

Ed

[Topless]

Hey Ed, where is your MAF housing? I don't see it in the pic. Intake looks good though.

So far I am still committed to stock intake and paper filters. Kind of a competition rule freak I guess. I just change them annually.

[edevlin]

There is a very nice CNC machined opening for the MAF sensor with the intake. You can just see the black sensor sticking up toward the back of the box on the blue aluminum housing. Its a great intake, built to higher standards than I need. I think it was really designed for larger motors and turbo applications, but still works well for smaller, normally aspirated engines. I sure dont know why anyone would need a carbon fiber housing around the filter element. The fit is good, but weight savings?

Ed