May want to rethink that K&N Air Filter you're using

Interesting test.

 

Good article and not the first I've seen that had similar results. Many performance cars already have decent air filters as standard.

 

You may be reading the chart backwards. The K&N had the least restriction to flow (the last graph in your link). While that puts the K&N filter at the bottom of your graph, that's actually a *good* thing.

 

This has been posted and argued over before...search the archives for the thread. This test was done almost a year ago...(I think).

 

I did back to back chassis dynos two years ago on K/N and stock paper. Best I remember we found K/N was about 7 hp worth or so at rear wheels - see archives.
Your results may vary.
best
rt

 

A few of the Porsche guys claim that the oil from the K & N filter builds up on the MAFS causing bad signals. Has anyone else heard about this?

 

Yes, but only if you don't follow the instructions, and over oil the filter, or apply the oil on the back side of the pleats. You should not experience this if used according to instructions.

 

Some Ferrari models (e.g. the 348) have self-cleaning MAFs. For other models, you'll just want to be extra careful to not over-oil your cloth K&N filter.

 

I put K&N filters in the same category as Zymol wax. Overhyped and overpriced!

Any perceived benefits are only illusionary...........

 

Overpriced? For most Ferrari applications they run $40 to $50. A factory UFI air filter can easily run over $100.

Compare for a F355:

UFI around $60

K&N $43.04 (and reusable)

Not currently using them on my current cars, but have used them previously on my 308, 328, VW, Honda and Nissan.

 

The MAF sensor issue is a serious problem. I have a K&N on my 85 Corvette and had consistent problems with the oil fouling the MAF sensor. To allay Dave's fears, I had oiled the filter in accordance with their recommendations. Under those circumstances, the oil would often accumulate on the MAF, making the car completely undriveable. It would buck and surge as if the throttle position sensor had failed.

The Corvette does have a self-cleaning MAF, so the solution is to turn the car off for four or five minutes and let the MAF burn off the oil. The car will then start and run normally for a while. How long is anyone's guess.

My solution was to clean the filter using K&N's re-oiling kit and then to BARELY oil the filter at all. This is contradictory to their instructions of evenly oiling the filter all around. I can't get rid of the K&N because it seems to be the only product that fits my supercharger intake, but I don't like it. The problem is widespread enough to be addressed on their website, but they are militantly unhelpful about it. I am not a satisfied customer overall.

 

It's generally accepted on the BMW forum that engines run with K+N filters don't last as long because they allow more dirt to pass. I suppose whether you prefer 7hp or longer engine life depends on how long you plan to keep the car.

 

Does K&N still offer the oil in a spray can? That is what I have used in the past, which make applying lightly, very easy. I noticed recently they sell the stuff in a squeeze bottle, which (to me) would be easier to apply too heavily.

 

My Honda Accord had close to 165k miles when I sold it two years ago...I hear it is still running fine to this day, and still has the K&N filter in it. My Nissan Maxima ran over 115k miles with a K&N filter and was still running fine when I sold it. None of these cars burned oil or anything.

I am on a E39 forum, and have never heard of anyone stating as "generally accepted" that a oiled filter like the K&N shortens engine life (though there seems to be the same debates). Probably 1/3 of the people on the forum run a "cold air intake" using one of the many brands of pleated gauze/oiled filters on it. Many of these cars have in excess of 100k miles on them.

 

There are only a handful of 100,000+ mile Ferraris...but vast amounts of high mileage BMWs...

So even if 7% more dirt was a problem, you'd be hard-pressed to find someone who put enough miles on a Ferrari to notice.

 

Based on what objective testing criteria?

 

more flow equals LESS filtration its as simple as that.

 

Yes, their "maintenance kit" is available that way.

 

that's just not right.

Take a steel plate with a 1mm hole it in. Airflow through the plate is lousy, but a >1mm ball won't go through, so it works. Now drill as many separate 1mm holes into the plate as you can. Airflow is good, and the ball still won't go through. Thus the statment that more airflow = less filtration is false.

The purpose of the air filter is to remove particles larger than size X. A paper filter accomplishes this by throwing enough fibers together so it's unlikely for there to be a hole bigger than X anywhere in the surface...but some percentage of the surface is effectively plugged up by fibers that are too close together.

Remember the original catalytic converters with the pellets and steel wool guts? You needed anough steel wool to prevent the pellets from blowing out, but it was crap for airflow. Compare that to the flow of the honeycomb matrix materials used today that you can look straight through.

While the k&n isn't an engineered matrix material, I assume it does exactly what it claims to do. Their web site describes how it works.
To compare the k&n to a different type of filter, you'd need to compare the flow as well as the particle size the filter will pass.

wrt the porsche problem, just replacing the filter in a boxster has been known to dislodge enough dirt/dust to cake up the MAF. Oil from a k&n will do it too. If the design of the air intake is sensitive to filter oil like in cgperry's case, then don't use one unless you have to.

Comments about a k&n reducing engine life imho are also a bit daft. There's simply too many variables to prove it....and I also assume that anyone who bothers to squeeze a little extra hp out of their car with an air filter is driving the car a lot harder than most, so their engine life would be shorter for other reasons.

I think snj5's response is the important one - assuming the particle sizes getting through both filters are below some threshold likely to cause problems downstream.

For the record, I don't use a k&n.

 

I, for one, will not be rethinking my use of K&N's. With nearly 150k on my 97 Maxima with a cone K&N and no issues of any kind related to filtration. Also my Tr that might get 2k-3k a year on clean dry roads with an intake at the back of the car why should I worry ? I, like an earlier reply in this thread, saw small gains in both hp and torque when dynoed back to back against the stock filter.

 

Has anyone tried the AirHog filters by Fram?

 

I soooo... much want a K&N but I am terrified by fouling the MAF's ( I been down that road...they are expensive ( for such a sensor) and control the whole damn Ferrari engine "joy") I realize that this "oil fouling" business is all due to user failure and they over apply the oil...I think I might try the K&N withthe spray as discussed earlier, but those MAF's can make your life hell if they are not happy.

 

While I have had K&Ns in my BB512i for sometime now with no problems, I had to remove them from my BMW M5 because they kept fouling the MAF sensors. So, it may be that they are fine for cars with carbs and cars with non-MAF or mechanical FI systems, but not for modern MAF systems.