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Old 02-25-2004, 08:57 AM   #1
macrwrx
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Default Does a K & N filter really increase power or does it do more harm than good?

I just put in a k & N and I'm still wondering if its working better or worse it is hard for me to tell. Can anyone enlighten me ? Has anyone encountered a similar situation in their WRX? I've also heard that oil from the filter can get onto the MAF sensor, is that true if its a new filter?
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Old 02-25-2004, 09:18 AM   #2
1DOWNCLOWN
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i have a KnN and i like it
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Old 02-25-2004, 09:18 AM   #3
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I was talking to one of my local sube dealers a week or so ago, and he suggested puttin a K and N in, so it can't be all bad.

It's not going to make a noticeable difference though...unless your butt dyno is extra-sensitive
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Old 02-25-2004, 09:48 AM   #4
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Sorry bud, this is interior & exterior mods and care. You might not get very many responses here.
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Old 02-25-2004, 11:13 AM   #5
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theres a few people saying changing to a higher flow intake is foolish, and the only power increase youre going to get is from the intake leaning out your car.

i use a blitz sus and im still running 11:1 a/f at WOT, very rich *shrug*

Last edited by googe; 03-05-2004 at 10:42 PM.
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Old 02-25-2004, 03:05 PM   #6
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There have been different thoughts on K&N. Some folks like them, other folks don't. There was a test done on filter panels, and K&N did very well with airflow. But unfortunately, it also allowed a little more particles to go through than the stock paper filter. It may not seem a lot, but it will build up over time. Other folks have complained that the oil from the K&N messed up their MAF sensor.

I have a MAP sensor, so I'm not sure if that makes it better. I can tell you that I do notice my car being more response with the K&N filter, but after my dealer told me that I needed an engine flush (due to too much crap in the engine), I took it out. I did take the K&N filter out before I let the dealer check my car, so they don't know I had the K&N.

Some other folks have recommended using Green filter, which is pretty much similar to K&N as it is composed of cotton and uses oil. The only differences are the color and apparently the quality (Green's appears to have a more tightly woven cotton, which in theory should filter better than K&N).
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Old 02-26-2004, 12:41 AM   #7
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Quote:
Originally posted by hunts
but after my dealer told me that I needed an engine flush (due to too much crap in the engine), I took it out.
How could they tell you that?????
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Old 02-26-2004, 11:35 AM   #8
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I think its in the no real harm and no real good realm.

Better flow will help later mods.

Was my 1st mod though
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Old 02-26-2004, 01:33 PM   #9
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I'm one of the hard headed people who thinks that changing the intake system at or before the maf in any way without getting control of the fuel system isn't generally a good idea. Sorry for being long winded, but this is what I think you might wanna know before puting a k&n filter in your car.

Subaru made the wrx in a weird way. They decided to make the fueling closed loop while under about 5000rpm and about throttle and open loop while above 60% throttle or 5000rpm. This means that the ecu is going for about 14.8 to 1 air/fuel ratio all the time while under 60% throttle 5000rpm, and works off of fuel map while under hard throttle(not checking the a/f ratio).

While under partial throttle, the ecu uses the front o2 sensor to determine what the a/f ratio is. Then it adds or removes fuel depending on a few things(like throttle position, manifold pressure, rpm). At the same time, the ecu is remembering how much air is going into the car(by checking the maf reading(mass air flow sensor)) at a given rpm and boost, and how much fuel it puts out compaired to a base map. Depending on how much fuel it puts out at any given rpm and boost and how much air it sees(with the maf), it then adjusts how the car is fueled while above 60% throttle or 5000rpm. This is called the fuel trim. It is there so that while under partial throttle the ecu can detect changes in the environment like weather and altitude, and apply it to the fuel settings b4 the car goes to boost(for safety).

Under hard throttle, the ecu sees the air coming in, how much boost there is, what rpm the engine's at, and uses these along with the fuel map and the fuel trim to determine how much fuel to put out at any given point. If there's a better then stock flowing filter, at there will be more pressure in the maf piping and the maf sensor will see more air from the denser charge(the engine/turbo sucking won't make the pressure drop as much). So at part throttle with a better flowing filter, the ecu would think there's more air going in for the same amount of fuel(to make the normal a/f fuel ratio) getting the ecu to remove fuel at hard throttle. Then at hard throttle the ecu will be using a different part of the fuel map(from the change in pressure at any given point), and the fuel trim will be different then stock making the fueling way different then normal at any given point.

The ecu also uses the maf reading(the the that reads air in the intake) along with the map, rpm, and what not to determine the ignition timing advance at any given point. Since the ecu is made to work with the stock intake and filter, having a better flowing filter will change the ignition timing of the car at any given point compared to if the stock filter was in. So, with a k&n filter, the stock ecu will have less ignition adnvance(more retarded timing) all the time since the pressure in the maf will be higher, and possibly a leaner/richer/choppier air/fuel ratio at boost.

What does this mean to me? The air/fuel ratio and ignition timing a car runs at any given point is important to its performance and safety. This is especially true with turbocharged cars. The stock ecu might not fuel or spark the engine perfectly in some peoples minds, but changing the fueling and timing blindly by changing the intake in any way(and the way the ecu sees air coming into the car)without getting control of the fueling just isn't a good idea(imo). This is all just my opinion after getting all the facts I've been able to get, and I'm not expert. Sorry for not quoting where I got my info from.

peace
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Old 02-26-2004, 02:22 PM   #10
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FWIW, I used to own a Nissan se-r and for the first 30k i ran only stock Nissan OE filters. The thick papery kind. Later I switched to a K&N panel filter. Every 30k I cleaned the throttle body and MAF sensor. After 30k with the OE filters the MAF sensor would always be clean. You could wipe the interior of the sensor with a white paper towel and after you were done it would still be white. After using the K&N for 30k, wiping with a white paper towel revealed fine black dust on the interior of the sensor. Switched back to the OE filters and never had the problem again.
I am going to stick with the OE filter because I don't want that crap to coat the turbine blades and maf sensor on my WRX.

Blair
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Old 02-26-2004, 03:07 PM   #11
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hippy,

You are spreading mis-information here.

Adding a K&N or other oil-cotton filter might increase available air, but if you don't change the intake it isn't going to mess up the MAF readings. Things that mess up the MAF readings include things that change the length or diameter of the physical pipe, meaning that more or less air can flow for a single given MAF reading. Just allowing more airflow through the stock intake system will only allow higher MAFs, it won't change what those MAFs mean. And as long as the ratios of air volume to MAF voltage are correct, the fuel mapping will be correct for those MAFs.

Now, if you over-oil a K&N filter, it can, in fact, gum up the MAF. I use an Airraid filter, it's almost the same as K&N. I cleaned it and re-oiled it, and I guess I overdid it - I started seeing knock where I usually would not. I pulled the MAF, and the MAF sensor was VISABLY gunked up with oil.

I pulled it out, dropped it in a ziploc bag with some NON-chlorinated Brakleen, and shook it gently for 30 seconds. I pulled it out, let it evaporate for 15 minutes, and reinstalled it. I've never had the problem since, and 8000 miles later my MAF sensor is still visably clean.

-Sean
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Old 02-26-2004, 03:27 PM   #12
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Ya hes talking about the OE style filter. 0 harm in it, 0 benefit too.
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Old 02-26-2004, 03:37 PM   #13
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Yup - an overoiled <insert filter brand here/> filter will screw the MAF. Personally...I'm going back to a stock filter when I swap out the Blitz LM panel filter I have in right now.
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Old 02-26-2004, 03:39 PM   #14
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my .02 c

I have had the K&N filters before and getting the right amount of oil on them can be fussy. Too much oil and it will coat the intake, not enough and you worry that the air will not be cleaned enough. Also "cleaning" them well is a pain.

I have had them on my other car and motorcycle for years and I am sick of dealing with it. I like them on the bike since they are one per carb, visible and cool.

Paper works, is cheap, and is easy.
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Old 02-26-2004, 04:20 PM   #15
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Yeah- unless you're needing just slightly more air than the stock paper filter will flow, it's not worth the trouble of a K&N-type filter on our cars. You live, you learn, you buy paper.

-Sean
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Old 02-26-2004, 04:26 PM   #16
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Quote:
Originally posted by big_adventure
hippy,

You are spreading mis-information here.

Adding a K&N or other oil-cotton filter might increase available air, but if you don't change the intake it isn't going to mess up the MAF readings........

-Sean
Like I said, I'm no expert. I can tell you that the maf sensor doesn't know the pressure in the piping and changing the restriction will change the pressure in the piping. I dunno what else to say except every time I post this information someone fights me.... Maybe I'm wrong?
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Old 02-26-2004, 05:48 PM   #17
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I have a sort of related issue. Me being the retard that I am, I tried to unscrew the screws to get to the MAF sensor, and one of the screws would not budge, I accidentally turned the screwdriver too hard and stripped the screw, so now it's just about impossible for me to unscrew it with a screwdriver. Any suggestions on how I can get this screw out? Thanks!

PS- I use a K&N, and for some reason I've noticed a decrease in performance of the car, so thats why I wanted to check the MAF sensor and see if anything was wrong w/ it.
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Old 02-26-2004, 06:15 PM   #18
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k and n=bad
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Old 02-26-2004, 06:49 PM   #19
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wait, hold on... are we talking about the k&n drop in, or cone filter?
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Old 02-26-2004, 08:44 PM   #20
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Drop in or cone, same thing. The dodge pickup truck community is really against K and N. It has been a hot topic for quit some time. Their view is that the K&N filter, lets too much dirt and grim in, causing maf's to go bad over time.
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Old 02-26-2004, 10:04 PM   #21
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Quote:
Originally posted by Aaron'sWRX
Drop in or cone, same thing. The dodge pickup truck community is really against K and N. It has been a hot topic for quit some time. Their view is that the K&N filter, lets too much dirt and grim in, causing maf's to go bad over time.


Ummmm... I'm not trying to start a pissing match here but... I am about 99% sure the newer EFI Dodge trucks are Speed Density. My '95 Jeep Grand Cherokee w/ a 318 was so was my buddies '00 Ram. Even the new Hemi motor is SD...
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Old 02-26-2004, 10:08 PM   #22
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I am with the stock one, its not hard at all to over oil the filter, and if you drive hard it gets dirty in an easy 20k miles not the 50k k&n clame.
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Old 02-26-2004, 11:34 PM   #23
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well, if you're worried about not being able to compensate for the 'extra' air that it will make the car run lean/rich/ or whatever, then get your ecu reflash with cobb. and if the problem is over-oiling the filter when you clean it, then don't! give the filter some time to drain all the excess oil and let it dry a little before installing it.

why would subaru sell a 'performance' filter if it doesn't help
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Old 02-26-2004, 11:39 PM   #24
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Quote:
Originally posted by GotWRX03
well, if you're worried about not being able to compensate for the 'extra' air that it will make the car run lean/rich/ or whatever, then get your ecu reflash with cobb. and if the problem is over-oiling the filter when you clean it, then don't! give the filter some time to drain all the excess oil and let it dry a little before installing it.

why would subaru sell a 'performance' filter if it doesn't help


They sell a K&N filter? and cobb only tunes for pannel filters not the tube intake things. Them and most tuners dont bother with the mess of trying to tune for them.
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Old 02-26-2004, 11:40 PM   #25
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Quote:
Originally posted by GotWRX03
why would subaru sell a 'performance' filter if it doesn't help
To make money perhaps... ?
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