I just put in the drop in K&N air filter into my '03 CL-S. I bought the thing to improve my MPG, any gain in HP would be icing. Reusability was also a selling point.

I just did a K&N search here and on the TL forums and note a lot of mixed thoughts concerning this product. I saw a number of posts on the TL forum that suggest the K&N design lets in more dirt and results in premature engine wear. This scares me.

My review of forum posts has left me with this -

PRO:
1) improve MPG by 2-4
2) quality filter with EXCELLENT dirt filtering application
3) reusable till the death of the car
4) possibly improve horsepower by 2 HP
5) possibly improve acceleration curve
6) possibly add more thoatiness to engine sound (I have not noticed this)

(I got the filter for #'s 1, 2, and 3)

CON:
1) minor gains in MPG/HP are not noticible
2) K&N design does not filter enough dirt
3) if you are increasing airflow you are increasing DIRT flow and making a dirtier engine
4) some mass sensors destroyed by K&N oil (K&N's website says this is untrue)
5) premature engine failure due to poor air filtering does not justify K&N purchase
6) stock OEM air filters are more than adequate for filtering and air flow into our engines.

I am not really concened about increases in HP or sound. I don't want a CAI (at least now) and since I already have the thing, I don't want to compare the Comptech foam filter vs. the K&N.

With respect to (3) in the CON list (more airflow = more dirt = bad) - don't the CAI's improve airflow? don't the CAI's have a K&N filter at the end? if this is true, wouldn't a CAI cause the same premature engine wear with increased dirt?

I want to know: will the K&N destroy my engine by f'ing up my mass sensor and letting in a shitload of dirt to scrape away at my cylinders? If there are enough negatives about this thing, I am going back to my OEM stock filter.

Any reports of Acura engine failure with the K&N drop in? Any mass sensors destroyed?

Thanks, I to the wise one's knowledge.

 

I have the Comptech drop-in hi-flow filter and it's been excellent. I get 28-30mpg consistently when I drive mostly highway speeds and have good gas.

I dunno about it letting more dirt in - I recently cleaned it for the first time in several thousand miles and it was mad dirty underneath but the top side was still nice and clean. It filters really well. I dunno if there's any real gain in hp but it breathes a bit better probably and with my removed resonator it sounds good too.

 

A CAI is the best of both worlds.........and it sounds awesome too

 

Thanks for the recommendations, but...I just wanted to know your opinion about the dirt filtering capabilities of the K&N (versus stock, I guess).

Am I damaging my engine with this thing?

 

K & N filters DO NOT pass dirt! They were originaly made for motorcycles racing in the California desert and do a excellent job of filtering. I don't know about HP, but the K & N in my wife's Integra has been in there for 130,000 miles with cleanings every 30,000 miles and it still looks new when cleaned.
Dan

 

I got the drop-in K&N because I didn't want the extra sound from a CAI. All the Pro's you listed are probably true (but I don't think mpg is increased by much). Your Con's list is way overblown, IMO. If the filter is properly maintained you will never experience conditions 2, 3, 4, and 5. I've put over a 100k miles on my other car (5.0 Mustang) with a K&N panel filter and about 15k on the CL-S with no problems at all. I've never once seen the inside of the panel filters dirty nor any residue on the inside of the throttle bodies.

 

I have heard two stories of dirty engines and engine problems with K&N. But then again I've had two cars with K&N and no problems. Amsoil has a filter with a foam oil screen that's supposed to be better (http://www.amsoil.com/products/ts.html). I have no idea what to believe. Has anyone tested the filtering of all these aftermarket filters -CAI, drop-in etc?

 

Just curious but did you hear the stories about the dirty engines first-hand from the owners?

My thoughts on foam (Amsoil, Comptech, et al) vs. cotton gauze (K&N) are simple (maybe too simple). Hold both up to a light and see which one lets more light through. The cotton gauze filter does. That also means the air should flow through easier. Plus, the air flows straight through the gauze whereas it needs to circulate around the small cells in the foam. As mentioned above, I've never had any problems with dirt getting through the K&Ns either.

I'd be interested to see independent tests on the filters also (not the ones from the company's web sites).

Here's a shot comparing our stock filter to the K&N panel filter:

 

Some manufacturers do not allow the use of any oil-impregnated air filters because of the way oil in the airstream eventually coats the MAF filament causing CE lights to come on. Ford, for example, places a sticker on some air filter housings with specific warnings about this. The cure when the CE light comes on is to gently clean the filament with a cotton swab daubed in gas.

I also understand that there are 2 specific types of MAF designs (I forgot the differences) but the more modern one is more susceptible to this problem. I don't know what Acura uses or their recommendations in this regard.

As to the passing of more dirt, K & N does admit to having larger openings but claim to filter more due to "diffusion".

>The most important principle for our use is diffusion, which deals with the laws of physics that govern the motion of very small dirt particles. Small particles are highly affected by the forces in the air stream. Forces such as velocity changes, pressure changes, turbulence caused by other particles and interaction with the air molecules cause these very small particles to become random and chaotic. As the result these particles do not follow the air stream and their erratic motion causes them to collide with the filter’s fibers.

This phenomenon enables an air filter to capture dirt particles that are much smaller than the openings in the media.<

I don't know if I buy all that or their claim that the filter somehow "straightens" the air flow.

Paper filters are cheap and easy to get. Still, I would consider a K & N.

 

Check out http://www.acura-tl.com/forum/showth...n&pagenumber=1 for a rather heated debate about the pros and cons of the K&N filter. This is the thread that scared me.

Anyone have any thoughts about my question with respect to CAI? Doesn't the CAI have a K&N at the end, and with the higher airflow of a CAI, wouldn't all you CAI folks have 'dirty' engines (assuming that the K&N is not a good dirt filter)?

 

Oh okay so K&N filter is different than my Comptech. My Comptech filter is safer.

 

Thanks for pointing that discussion out. I read it all and will continue to use K&Ns on my cars, based on personal experience.

One of the links in that thread listed flow rates. It said "An average foam filter will flow 4.38 cfm/sq-in. A good paper filter will flow 4.95 cfm/sq-in. An oiled cotton gauze (K&N) will flow 6.03 cfm/sq-in." ( http://www.pro-flow.com/mustmath.htm ) Who knows where those numbers came from though...

Good question about the CAIs. The AEM CAI does use a K&N-type filter (was an actual K&N previously). I think Weapons-R uses a foam filter. Has anybody with an AEM unit seen oil or residue on the insides of their tubing or throttle bodies when cleaning the filters?

 

Yes...that's my thoght. If the K&N is really a dirt sieve (as insinuated on the TL forum) then a CAI setup should really have a lot of dirt in the tubing/throttle/engine/oil/etc. There also should be some fouled mass sensors from the CAI's too...assuming the logic of the K&N nay-sayers.

 

I've used K&N filters for about 10 years now. 2 of them had over 120,000 and no problems. Never anything like what was mentioned. Always clean into the throttle body. In fact, I'd even go so far as to say the motor oil remains cleaner after installation which speaks to LESS dirt passing into the engine and past the rings. In my motorcycles (1 dirt, 1 street), they performed remarkably. (noticable throttle response gains). Again, no more visible dirt than with factory foam and cleaner motor oil.

My CL-S currently has 37,000 and has had a K&N since new. I have never noticed huge improvements in mileage or performance (but have noticed small in both areas) but do like that I can clean it whenever I like, and that I'm not paying $20 for a $2 paper filter. My mileage did go from 28 to 30, though some of that could be due to break in.

 

K&N w/ resonator removed and custom tubing for better flow here. and not as loud as a CAI

plus it pays for it self w/ the gas saving