Is a K&N air filter worth it?

capnnard · 03-25-2009, 11:05 AM

A dirty air filter was the culprit to a tough spring start to my 911SC. I had a Mahle on hand and am ordering a replacement from our host. I searched this thread for thoughts on the washable/lifetime K&N but didn't find anything. Does anyone have a strong opinion on whether this is a worthwhile investment? If there is a thread I've missed please point me in the right direction.

Thanks,

Ken

Gunter · Gunter's Garage

It's been covered a few times.
No proof that K&N filters improve performance or are better than stock.
Falls into the category of "Cool Collars" for oil filters.

fireant911 · 03-25-2009, 11:12 AM

I have a strong opinion although others may disagree. I tossed my 911 SC's K&N filter in the trash and will never have one in any vehicle. The amount of trash allowed to pass was evident and alarming; however, the efficiency is purported to improve with time (though I honestly have trouble with the debris passing before the filter becomes a proper filter).

the · 03-25-2009, 11:15 AM

There is simply nothing wrong with a stock air filter. Porsche is smart, they built an airbox and spec'd an air filter that does not choke the engine in any way (i.e., it flows far more than a stock engine could ever use). Numerous dyno tests have proven that over the years. K&N is mostly a marketing company, their product is the answer to a question no one has asked.

myamoto1 · myamoto1's Garage

I'd never subject my car to a K&N filter, unless it was a track car that had the engine torn down after every race. Even then, it would be one of my last choices as a filter. K&N are crap as filters. The reason they let in so much air is because they don't filter woth a darn.

I used to off-road a lot and was amazed at how many guys were running K&N filters. I asked them to pull their throttle body (or at least the hose connecting from the filter). They were always amazed at how much dirt was in there.

If you're looking for a dry filter, stick with stock (Mahle) or if you want an "upgraded" filter, I've had good luck w/ the Amsoil wet (oiled) filters. Although, I've never tried an Amsoil filter on my Porsche.

cbush · 03-25-2009, 11:58 AM

No to the K&N filter. The oil from it ruined one of the sensors in my Boxster. Not sure how it would effect my 911s, but not interested in finding out.

bklyn · 03-25-2009, 12:11 PM

I removed the K&N on both of my vehicles, it destroyed my wifes maf sensor on her Boxster, dont think it did anything to my Targa but was not taking the chances.

m110 · 03-25-2009, 12:15 PM

The hot wire in the mass air flow sensor for those cars with it (not an SC) can be ruined by the oil droplets coming off a properly maintained K and N.

porkee · 03-25-2009, 12:58 PM

Hey Ken, I ordered one and it did not fit the air box properly. Flimsy pos imo. It got returned, and now back to the nice reinforced stock filter.

burgermeister · burgermeister's Garage

I wouldn't put one on either, same reasons already stated above. Hold one up to the light - you can see lots of tiny holes (at least I could on the one that came with my car).

Your filter must have been incredibly dirty to cause starting issues! Most filters will last 100K or more ... my last DD went to its sale at 140K on the original filter, and we live on a dusty dirt road.

mb911 · mb911's Garage

We tested K&N's vs paper in an avaition type setting in a former life then tore the engines down. the K&N let more dirt through and you could see the scuffing on the pistons to prove it. Never would I use one if I have different options.

Nickatnyt · 03-25-2009, 02:59 PM

hasta la vista K&N!

88-diamondblue · 03-25-2009, 02:59 PM

I would use the stock paper filter. Here is a link to some visual proof of how much dirt gets through the filter. The K&N and Amsoil filter appeared to be the worst. http://www.bobistheoilguy.com/airfilter/airtest3.htm

john walker's workshop · 03-25-2009, 03:12 PM

picture blowing dirty air through a sieve. hold one up to a light and you could probably see all the constellations.

GaryR · GaryR's Garage

Quote:

Originally Posted by john walker's workshop

picture blowing dirty air through a sieve. hold one up to a light and you could probably see all the constellations.

Very good John! My shop showed me the intake of a customer's SC that had switched to K&N (to gain 10 HP - like that will ever happen) and it was full of fine grit. Learned that lesson quick, NO K&N!

Talewinds · Talewinds's Garage

Ok, no K&N then. So is there a way to ditch the clusterf that is the stock airbox and replace it with a smaller, simpler, more concise paper filter that would allow a cleaner, more serviceable engine compartment???

mossguy · 03-25-2009, 03:18 PM

This thread on the K&N Filter is a classic!!

K&N Air Filters - Oil or Not?

Best,
Tom

Brother · 03-25-2009, 03:37 PM

dirt showed up on my oil analysis when I had a K+N in a slightly dust area. It was gone after that. Clean oil tests since then.

jtratza · 03-25-2009, 03:39 PM

I beg to differ. While I don't think a K&N filter will add any performance over the Porsche system (and have seen lots of test that indicate that is the case) I've had one on my engine for over 150,000 miles with no problems to the MAF hot wire installed in the early 1990's nor to the engine internals. A few years ago I had the "opportunity" and lucky for me the money to get a full rebuild as a result of a broken head stud and lots of oil leaks. Neither of those problems can be attributed to the K&N. When the engine was opened we inspected everything and noticed almost no wear except on a couple of crank bearings that showed very light wear for the miles. On the MAF I'm running the stock air box doesn't fit so have to run an after market filter. The K&N does allow for more engine noise but as others have pointed out probably no hp advantage.

sc_rufctr · 03-25-2009, 03:42 PM

Just out of boredom and curiosity I built this intake using a S&B air filter...

It was on my car for about 6 weeks... No performance gain! If anything a slight loss at higher RPM on the freeway. This filter has a surface area 30% bigger than stock and as you can see the pipe is massive...

After my experiences with this setup I'm very suspicious of claimed horsepower gains from any after market filter.

I have a stock airbox back on the car with a K&N filter. I keep it cleaned and oiled and haven't noticed any extra dirt getting into the TB... Believe me if I even had a suspicion that the K&N wasn't as good as stock it would be in the bin within 30 seconds...