K&N Air Filter

[HelionTBone]

Hey guys. I've been hearing a bit about K&N air filters and was thinking about getting one for my MP5 that I bought last month. After searching through the forum I realized that there have been very mixed reviews and I wasn't able to find a definitive answer on whether or not a drop in version would help my MP5 (bluep5)

So I decided to just go for it and post my results for non-modders like myself. First off I should say that my car (2003 AT) is totally stock with the exception of the tires I just put on it (Toyo Tourivo 205-55-16 which offered a huge reduction in road noise). Second, I have felt like my mp5 works way harder than it should at high speed. Nothing scientific, just a gut feeling. Third, I've been very unimpressed with the gas mileage; I have the automatic transmission.

I bought the K&N drop in air filter, but before replacing the paper filter I took the car down a section of highway and set the cruise at 65 with the AC on. I noticed, as usual, that the engine was running between 3,300 and 3,400 RPMs. I then drove home and put in the K&N filter. While examining the paper filter it looked practically new but did have a small amount of dirt on it. If I had to guess I would say it had been used for 5-8K miles. As soon as I left the house i noticed a definite difference in the engine. I don't have a dyno to run on :) but it just seemed to be more responsive. Some people say you can get a 5 - 10 hp improvement with these filters - I find that hard to comment on, but there was a noticed difference. Then I took it on the same stretch of highway, set the cruise at 65 with the AC on and it was running at 2,700 to 2,800 RPMs.

So my observations are:
1. engine feels slightly more responsive
2. doesn't seem to work as hard in general
3. runs much more efficient at high speeds.

I can't comment on gas mileage yet, but I will add to this in the future once I have some data. I can say that my assumption is that it will have hopefully a 1 to 3 mpg improvement just based on the sheer fact that I was able to drop below 3,000 RPMs at high speed (usually once you go over 3,000 your gas mileage plummets). I drive 70% highway driving, so if I do see even a 2 mpg improvement I will realize about a $200 savings on gas annually (with the amount of miles I drive). That makes the $35 filter pretty attractive. Plus it comes with a million mile warranty, so its the last filter you ever have to buy and you can feel good about not throwing disposables in a landfill.

So, in conclusion, if you are a non-modder like me it seems like this is a no brainer. If you are a modder I would skip this entirely and go with a cold air intake system.

Thanks for the great site!

[flash75]

I don't see how using a K & N filter can cause the engine rpm to change at road speeds, it doesn't change gearing. My 02 P5 automatic with stock size tires runs around 3000-3100 at 70 mph. The red line is 6500 so it is not working too hard at 70 mph.

I tried a K & N in my P5 several years ago and didn't notice any change in engine sound, performance, rpm or fuel mileage. If you over lube a K & N, you may contaminate the oxygen sensor. I removed mine and switched back to a stock filter.

I find the P5 has ideal gearing for driving in the mountains. I just took my M3 sedan on a trip to Colorado and it only turns around 2600 at 70, good for fuel mileage but when I got to the mountains I wished for the gearing in the P5, it's much better for performance.

Clifton

[HelionTBone]

I don't see how using a K & N filter can cause the engine rpm to change at road speeds, it doesn't change gearing. My 02 P5 automatic with stock size tires runs around 3000-3100 at 70 mph. The red line is 6500 so it is not working too hard at 70 mph.

I tried a K & N in my P5 several years ago and didn't notice any change in engine sound, performance, rpm or fuel mileage. If you over lube a K & N, you may contaminate the oxygen sensor. I removed mine and switched back to a stock filter.

I find the P5 has ideal gearing for driving in the mountains. I just took my M3 sedan on a trip to Colorado and it only turns around 2600 at 70, good for fuel mileage but when I got to the mountains I wished for the gearing in the P5, it's much better for performance.

Clifton
I appreciate your input, but I'm only telling what my observations are of a fairly controlled test. Do you by chance have a manual tranny? I'm finding that there is a significant difference in performance between the manual and auto. Thanks.

[chaztor]

I put one in about 600 miles ago. No noticeable difference. I would say a low HP car like our Pro5's are pumping less air than most high performance cars or large displacement engines. And whats an engine but a fancy air pump.
I would be VERY surprised if it was even +5 HP.

I have had experience with drop in K&N filters in 5 vehicles and only the turbo ones had a noticeable change vs. a clean paper element.

But don't get me wrong its still an improvement and I feel worth it if you are keeping the car for very long.

[chaztor]

Do you by chance have a manual tranny? I'm finding that there is a significant difference in performance between the manual and auto. Thanks.

Mines mani. and no other mods. M3 17" wheels.

[flash75]

I appreciate your input, but I'm only telling what my observations are of a fairly controlled test. Do you by chance have a manual tranny? I'm finding that there is a significant difference in performance between the manual and auto. Thanks.

I have an automatic transmission.

Clifton

[HelionTBone]

Well, thanks for the reply's but I'm scratching my head (scratch).

I can't figure out why I'd have such a noticable difference when clearly you guys (and others on this site) saw none. I guess I'll just count my blessings.

[chaztor]

was your paper filter dirty like a 5$ copy of autocad?

[kura808]

hmm..i put in my drop in about 2 yrs ago and noticed a bit of a change..i think i got like 2 or 3 mpg more..not to mention, it sounded a lil different when u revved it and like he said, it felt a lil more responsive. when i took my old paper filter out, it wasnt that dirty either so i suppose the K&N made a lil difference.

anyways..most people say go wit the drop in filter cause supposedly our air boxes are pretty well designed i guess. somewhere i read u lose some torque wit an sri or cai? vs using the stock air box. i think tri-point was using the stock air box too(not sure which racing team used it). i'm a happy customer haha. i just wished i had the suction sound from an sri or cai haha..but its ok

btw i'm a '02.5 wit sportauto

[HelionTBone]

hmm..i put in my drop in about 2 yrs ago and noticed a bit of a change..i think i got like 2 or 3 mpg more..not to mention, it sounded a lil different when u revved it and like he said, it felt a lil more responsive. when i took my old paper filter out, it wasnt that dirty either so i suppose the K&N made a lil difference.

anyways..most people say go wit the drop in filter cause supposedly our air boxes are pretty well designed i guess. somewhere i read u lose some torque wit an sri or cai? vs using the stock air box. i think tri-point was using the stock air box too(not sure which racing team used it). i'm a happy customer haha. i just wished i had the suction sound from an sri or cai haha..but its ok

btw i'm a '02.5 wit sportauto
Ha ha ha... thanks for coming to my rescue, kura808! I was afraid that people were beginning to think that I was full of crap. Am I to understand that you are still using it after 2 years and are still achieving MPG results?

[kura808]

after using it for a while, mpg is pretty consistent. i mean every once in awhile, i do the math and it comes out pretty good. theres not much u can lose or gain after using it for so long lol..but honestly, i still think it made a difference. not a big difference but enough haha


Ha ha ha... thanks for coming to my rescue, kura808! I was afraid that people were beginning to think that I was full of crap. Am I to understand that you are still using it after 2 years and are still achieving MPG results?

[HelionTBone]

after using it for a while, mpg is pretty consistent. i mean every once in awhile, i do the math and it comes out pretty good. theres not much u can lose or gain after using it for so long lol..but honestly, i still think it made a difference. not a big difference but enough haha
Cool, well that's all I'm really trying to accomplish with a $35 part. I appreciate the feedback.

[RABID_MP5]

Good previous point on over-oiling maybe fouling the O2 sensor. Which also begs the point of how often should you typically clean & oil the element in normal operating conditions? (Mine is the K&N on the Injen CAI in the fender well, so it's gonna see more dirt than a stock box element too.)

[HelionTBone]

Good previous point on over-oiling maybe fouling the O2 sensor. Which also begs the point of how often should you typically clean & oil the element in normal operating conditions? (Mine is the K&N on the Injen CAI in the fender well, so it's gonna see more dirt than a stock box element too.)
I've heard people say you should clean every 15K miles, however the box says to clean it every 50K miles. Not sure how often you should oil it.

[flash75]

Follow the instructions on the K & N box.

Clifton

[IslandP5]

This looks like a good spot for my question.

Is there an expiry time frame on air filters? I was looking through my service records and almost 7 and a half years later my P5 still has the original filter. It looks fine and dandy, but not sure if there is also a time frame associated with changing them.

[flash75]

In Canada the shop manual specifies changing the air filter at 24 months or 48 km. My filter is usually dirty at change intervals. The dirt is on the underside of the filter, it looks clean on top, as it should.

Clifton

[IslandP5]

HAHA. Thanks. I'd be the first to recommend checking the manual, but wouldn't think to do it myself.

[Konkinator]

I put one in at my last oil change and I definitely have noticed a bit of a change. It isn't all that noticeable, but it think that the exhaust note is slightly lower and it pulls a bit better for me.

[dxaveP5]

K&N filter was installed on this past friday.
I notice more aggressive exhaust sound once passed 3K.
Everything seems to be more responsive, and it pulls better for me.
mpg will be testd tmrrw when i fill up. i usually average 31mpg city miles.
and im a man. tranny btw.

[DSlab]

I had similar result after switch to a K&N drop in filter. Noticeable improvement right after installing. Smoother acceleration, feels like the engine is working more efficiently. But then again, my old filter was really really dirty...... I'll shut up now...

[P-Funk!]

No expiration date for air filters ;) Hold it up to the sun - if you can see quite a bit of light through it - it is still good!

I did a K&N early on - with a ghetto short ram. Nice improvement. And no issues. Oil is still clean 3K miles since the last oil change. Just do the 50K mile clean and service. It pays for itself in saved $ from paper filters.

Mad HP, yo! NO.

[carsnrockmusic]

I put a cone filter in the place of the factory airbox...my mpg went up slightly. I'm experimenting with a stainless steel cone filter that was left over from a past vechile. The paper filter that was in the airbox was new but it's still slightly restrictive...it's paper afterall. If you intend on installing filters/intakes for HP gain you should probably purchase a six pack of good beer instead.

[HelionTBone]

Ok guys, so its been over a year since I dropped in my K&N and I can honestly say that I've seen no better than a 1 or 2 mpg increase (if even that). However, I do maintain my original stance that my performance has and continues to be slightly better. My engine has never worked so hard as it did before the switch. Less RPMS = less engine noise = more pleasant environment and hopefully a longer lasting engine. All in all I am a happy customer, however it is a minor inconvenience to have to clean and oil them every 15K or so.

Cheers (drinks)

[slavrenz]

Ok guys, so its been over a year since I dropped in my K&N and I can honestly say that I've seen no better than a 1 or 2 mpg increase (if even that). However, I do maintain my original stance that my performance has and continues to be slightly better. My engine has never worked so hard as it did before the switch. Less RPMS = less engine noise = more pleasant environment and hopefully a longer lasting engine. All in all I am a happy customer, however it is a minor inconvenience to have to clean and oil them every 15K or so.

Cheers (drinks)

Why don't you clean and oil every 50k like the other posters are talking about?

[RABID_MP5]

I'm thinking the mpg increase wih the K&N would be minimal. In the days of the carb, a dirty filter meant the mixture would richen too much. But now you're just a filter ahead of the throttle plate. The maf and O2 sensors figure the mix. So a dirty/restrictive filter is now the equivalent of not being able to get the throttle all the way open. So I'm thinking high load - high RPM conditions of maximum CFM flow is when you'd really feel it.

[slavrenz]

I'm thinking the mpg increase wih the K&N would be minimal. In the days of the carb, a dirty filter meant the mixture would richen too much. But now you're just a filter ahead of the throttle plate. The maf and O2 sensors figure the mix. So a dirty/restrictive filter is now the equivalent of not being able to get the throttle all the way open. So I'm thinking high load - high RPM conditions of maximum CFM flow is when you'd really feel it.

But this is basically a description of most people's highway driving (high load/rpm), so I think it would make some difference.

[Matt V]

I'm sorry, but there is no way your RPM dropped by 500-600, there is no way in hell that an air filter could do that unless something was majorly wrong before.

[ToNeZ90]

I've heard people say you should clean every 15K miles, however the box says to clean it every 50K miles. Not sure how often you should oil it.

honestly it depends on ur driving enrivonment. if you're driving through stop and go traffic, construction zones, and places with dust in the air constantly, then you should at least check it more often to see how it is. I recently installed my ghetto rigged short ram (for awesome sound!!) and it says to clean and reoil every 10-20k, depending on driving conditions. I drive though construction zones and stop-go traffic at least 4 times a week. The filter has about 2k on it and it is starting to look a little dirty, which is good cuz it's doin its job :)

EDIT: oh i almost forgot......It does make a difference. you do loose a little 1-2k rpm torque but it makes up for it after 3k rpm. and mileage is better, like noticeable

[Brian_K]

hah placebo effect, when i installed my cai i thought my car had more pep, in reality it was just making more noise...

[slavrenz]

I'm sorry, but there is no way your RPM dropped by 500-600, there is no way in hell that an air filter could do that unless something was majorly wrong before.

It does seem to be a bit high...and I agree that I think there was some other problem with the motor to begin with. When I'm at 65 on the highway my RPMs are between 2800 and 3000.

[HelionTBone]

Thanks for the thoughts. I'm willing to submit to the "there must have been something else wrong" theory, but not the "placebo effect" theory. RPMs are RPMs - I took notes. All in all was the K&N much of a difference? Maybe, maybe not. Did it break the bank? nope.

As far as why would I clean it every 15K - only because I keep getting conflicting responses as to how often it should be cleaned. Its not that dirty at 15K, so maybe it could go to 50???

[i12drivemyMP5]

It's not necessarily mileage but environment that would dictate the cleaning intervals. If dusty or sloppy wet frwy use then lower cleaning intervals. If mostly good weather & pavement only driving then higher intervals are OK.

[ToNeZ90]

yeah dont go by the box. thats pretty much the max milage. Just check it occasionally or every 3k miles with your oil change and you should be able to see if you need to clean it. all depends on driving conditions.

[faridk89]

put a K&N Air Filter in my p5 today, didnt really notice a difference...only little thing is it does seem to pull better at low RPM's but i could be mistaken

[Ch555]

got me an used K&N today. it was just so cheap, same as paper so i give it a try. Think i have to wait till it gets little warmer, we have like a winter here and -25c(-13F?) outside :cool: Also i dont know how that filter oil reacts with cold temperatures. Will it freeze? lol

[slavrenz]

got me an used K&N today. it was just so cheap, same as paper so i give it a try. Think i have to wait till it gets little warmer, we have like a winter here and -25c(-13F?) outside :cool: Also i dont know how that filter oil reacts with cold temperatures. Will it freeze? lol

It only takes 15 seconds to swap out the air filter, honestly :) As far as freezing, if the oil in your air filter is freezing, that means the oil in your engine is freezing, which means that you've got bigger problems than your air filter ;)

[Ch555]

yea lol. no seriously i dont know what oil it is that is used for filters. it comes in spray can. in engine i have 0w40 so i think that part is covered, only filter to worry then :)

[slavrenz]

yea lol. no seriously i dont know what oil it is that is used for filters. it comes in spray can. in engine i have 0w40 so i think that part is covered, only filter to worry then :)

My point was that I wouldn't worry about the oil in your air filter freezing either :cool:

[bradicus18]

I hope you're not still running the same tire size. That size is over an inch in diameter larger than the stock size. You won't get an accurate reading with that size anyhow.

[HelionTBone]

I hope you're not still running the same tire size. That size is over an inch in diameter larger than the stock size. You won't get an accurate reading with that size anyhow.
Yes that's true. I factor in the 6 to 8 percent offset any time I'm looking at my mileage. It's slightly annoying, but it would be very expensive to fix and I really enjoy the larger tires (gasp). I also have to realize that when my spedo says I'm going 60 I'm really going about 65.