No K&N Controversy here?

[jblackburn]

I noticed a huge difference with the K&N filter in my old 4-cyl Accord. But its effect on the Volvo was pretty negligible I think, I noticed the turbo spooled a little earlier, but in terms of power I couldn't notice a huge difference. It's already set up to breathe pretty well.

[Cyman]

heh, for some reason I read all 3 pages of this argument.
K&N air filters are advertised as an automotive cure-all.. "better gas mileage, more horsepower, saves money, engines last longer, filters more junk." the list goes on and on, but in reality much of it is untrue.

first off, K&N air filters don't magically increase gas mileage. If I remember the stupid poster I saw in O'Rileys correctly the filter added 5 MPG on a particular model of mustang, but didn't mention statistics for any other car. nor did it mention under what driving conditions it would actually increase gas mileage, and until they do I'll consider this complete hokum as I've never actually seen any MPG gain when I've installed them. (I also think it's important to note that the main reason one installs these filters is because they allow MORE AIR into the engine. and if the engine gets more air, it will add more fuel, which adds more power.. and if your car is using more gas your MPG would actually go down, right?)

on the part about saving money, the math is quite simple. depending on how long you own the filter you will either save money or lose money.

Power gain is pretty much the only truth behind their advertising campaign, but even this can be false depending on the type of car you're putting it in and how much air the car actually needs.
Earlier in this thread someone mentioned that the pressure differential between K&N and stock is only .5 inches of water, but the statistic was missing a very important piece of data: the volume of air that was actually passing through the filter. as the amount of air passing through the filter increases, the pressure differential will also increase. for example: if you're breathing at a normal pace, it's easy to do so through your nose, and even if you were to open your mouth to breath, it wouldn't make much of a difference. however, when you need to breath quickly, the difference between breathing through your nose vs breathing through your mouth seems much greater.

On my 300zx, when the after market filter was put on, it only added 5-7ish horsepower, which was barely noticeable.. but since then I've modded the car and it now demands more air than it did when it was stock. if I were to switch back to the OEM air box I would lose 15-20 horsepower simply because the difference between the stock air box/filter vs the single pop is greater when the engine demands more air

K&N's don't filter the air as well as OEM, but that should be a no-brainer. you can't magically increase the volume of air that passes through a filter without increasing the surface area of the filter unless there is actually less material there to stop junk from going through. it's said that anything smaller than a certain size won't hurt the engine, but it doesn't really make sense that there will be absolutely no effect on an engine when more garbage is sucked into it.

in short, I don't plan on upgrading the filter in the 850, but I'm very happy with the one I have in the Z. for a daily driver, I don't really need the extra 5 horsepower, It's easier to just replace the stock filter than to take a K&N out to clean/oil it, and it doesn't filter the air as well. if you want your car to have a decent amount of horsepower, this should be one of the first things you buy. otherwise, I'd skip it.

[SpeedyPete]

Hi Guys: My story. I had a bad MAF. I replaced it along with cap,rotor, plugs...K&N air filter. After about 2000 Miles OH MY! the MAF went out.... I tried to clean it, but no cigar. You should note this was a new K&N Pre-oiled right from the box. I was able to exchange the MAF and I bought a new OEM filter. I replaced them in the parking lot and placed the K&N in the trash SLAM DUNK STYLE!!!! End of problem. Best Regards, SpeedyPete

[tjts1]

Cool story bro

[IVIUSTANG]

I've had my K&N air filter in my car for 120,000 KM and I still have the original MAF sensor in my car no problems whatsoever. I've cleaned and re-oiled my filter once in that time.

- Jesse

[matthew1]

I've had mine in for 10 years/ 55k miles. Same MAF, like Jesse. Re-oiled once too.

[C@lvin]

Trouble free miles for me on three vehicles:

2 yrs/28K miles 98 Volvo S70 (216K)
4 yrs/10K miles 94 Toyota Previa (179K)
3 yrs/40K miles 00 Honda Odyssey (192K)

The most significant affect that I expereinced was on the 94 Toyota Previa (4 cylinder). Couldn't really tell any difference on the Honda Odyssey (6 cylinder).

[QuirkySwede]

FILTERS BEST: plate welded over hole = no dirt gets in, but neither does air.

FLOWS BEST: totally open to atmosphere = no air is kept out, but neither is any dirt.

ENOUGH SMALL HOLES WILL FLOW AS MUCH AIR AS A BIG HOLE, and only "small" dirt particles can get through, nothing "big"ger.

So comparing a K&N to a Mann filter, and using the K&N's dimensions for both (H: 1.5", L: 13.625", W: 7.125", because I'm too lazy to go out and measure my non-K&N), let's compare the surface area of the two filters.

MannVsKandN.JPG (43.03 KiB) Viewed 1744 times

K&N has pleats running the length of the filter.
P(leats) x 2 x H(eight) x L(ength)
24 x 2 x 1.5" x 13.625" = 981.00 in^2

Mann has pleats running the width of the filter.
P(leats) x 2 x H(eight) x W(idth)
118 x 2 x 1.5" x 7.125 = 2,522.25 in^2

K&N has 39% the filter are compared to Mann.
Mann has 257% the filter area compared to K&N.

Now, how much "bigger" would the "holes" in the K&N have to be to "flow better" than something that has two-and-a-half times more surface area?

Here's a test. Disconnect the and wipe clean with a water-dampened paper towel (A) the inside of the tube just downstream of the Mass Air Flow sensor, let dry thoroughly, install a fresh Mann filter, and run your car back and forth 10 times down a dusty, dirty road. Disconnect tube, wipe with another towel (B), install new K&N filter, repeat 10x trip up and down same road, disconnect and wipe with yet another towel (C). Which is dirtier, B or C? For good measure, clean tube again and this time run the K&N first, wipe, then Mann, and wipe. Compare towels again.

Question: Why would an auto maker (e.g. Volvo) go to lengths to design a motor system efficient enough to balance mileage and power, then "choke" it with a "restrictive" air filter, especially when competing makers could do it so their motors out-perform [Volvo's]?

Question: If K&N is so good, why aren't they or a similarly-designed filter OEM?

Question: Since dirtier air wears things like piston rings and valve guides faster, how much does one have to save on air filters to offset the loss in performance in the long term from leaks (not to mention more PCV system fumes) as well as hastening the need for a head job?

Question: Are racers who use K&N filters concerned about piston ring and valve guide wear considering they rebuild their motors between race weekends? How often do non-racers rebuild theirs?

Question: With paved (non-dirt) roads and generally good air quality, how long could someone "get away" with running no filter at all?

Question: If oil is so good at "trapping" dirt, why did manufacturers stop using oil bath filtration systems in favor of paper filters DECADES ago?

Question: Do people who compare the two by replacing a "dirty" paper filter with a "clean" K&N also compare replacing a "dirty" K&N with a "clean" paper filter?

[abscate]

Add "air filter" to sex, religion, politics, and oil change intervals.....

[instarx]

Earlier in this thread someone mentioned that the pressure differential between K&N and stock is only .5 inches of water, but the statistic was missing a very important piece of data: the volume of air that was actually passing through the filter. as the amount of air passing through the filter increases, the pressure differential will also increase. for example: if you're breathing at a normal pace, it's easy to do so through your nose, and even if you were to open your mouth to breath, it wouldn't make much of a difference. however, when you need to breath quickly, the difference between breathing through your nose vs breathing through your mouth seems much greater.

Well here we go again. That was me who mentioned that the K&N only reduced pressure drop across the filter by an insignificant 0.5 inch of water. But you are wrong - I DID mention the volume of the air flowing through the filter - it's included in the Flow Rate (Q), which is volume/time.

I stick to my guns on this. All the perceived improvement in performance from an air filter that provides such a small improvement in restriction is in the heads of the people installing them. This phenomenon has two names in psychology: "Head factors", and "cognitive dissonance". Head factors mean you believe it will work therefore you are more likely to perceive it working. Cognitive dissonance occurs when you chose one item over another (H&K over Mann for example) - your brain then "knows" that you made the correct choice and the thing you chose is perceived as being superior. Neither is the experiment blind. The driver knows there is a new filter in the car that is supposed to increase mileage, so his driving behavior WILL change (not might change, will change).

Here is a question: If H&K really produced measureable improvements in MPG, don't you think they would be publishing actual data rather than simply writing "Improves Mileage" on their boxes? Even a provable 1 mpg improvement would make H&K tens of millions of dollars. But its all just marketing hype because H&K can't show that data because it doesn't exist.