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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Should I use a K&N air filter?



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      02-16-2012, 08:15 PM   #23
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a filter change isn't going to do anything to your car. Sure you may be more likely to get stuff into your engine (and I hope that never happens to anyone), but I've ran about 6k on my car driving from LA to merced in the past few months after putting the K&N filter and charcoal delete and I've had no problems. I know other people on these forums have run it for longer. I don't think it pulls any harder (at first i thought it did and maybe I've gotten used to it).

when i first did this, my car did have a deeper sound at first, but I think the ecu took note of this and regulated the amount of fuel that it needs to inject with the new air flow coming into the engine. Now my car sounds as it did stock IMO. There isn't much change in the higher RPMs but you can hear something different if you have a keen ear for it.

The only thing I wish I had was a euro box since it would be much easier to take out and clean the filter when I need to. Other than that, do as you please. Paper or not, I haven't been convinced to buy an aftermarket intake (unless i could afford gruppe M cause they sound beautiful =P).
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      02-17-2012, 09:53 AM   #24
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Originally Posted by spacemonkey1112 View Post
a filter change isn't going to do anything to your car. Sure you may be more likely to get stuff into your engine (and I hope that never happens to anyone), but I've ran about 6k on my car driving from LA to merced in the past few months after putting the K&N filter and charcoal delete and I've had no problems. I know other people on these forums have run it for longer. I don't think it pulls any harder (at first i thought it did and maybe I've gotten used to it).

when i first did this, my car did have a deeper sound at first, but I think the ecu took note of this and regulated the amount of fuel that it needs to inject with the new air flow coming into the engine. Now my car sounds as it did stock IMO. There isn't much change in the higher RPMs but you can hear something different if you have a keen ear for it.

The only thing I wish I had was a euro box since it would be much easier to take out and clean the filter when I need to. Other than that, do as you please. Paper or not, I haven't been convinced to buy an aftermarket intake (unless i could afford gruppe M cause they sound beautiful =P).
WOW so let me get this straight, you have driven your car for 6k miles with the K&N filter and experienced no problems? Thanks for sharing. Well I don't know about anyone else, but that's good enough for me! I mean if that doesn't qualify as an engineering study I don't know what does. I mean heck, what's wrong with a little extra dirt getting into your engine, right! It certainly sounds like a worth while modification in order to get a little extra engine sound.

Last edited by cssnms; 02-18-2012 at 08:09 AM.
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      02-18-2012, 09:39 AM   #25
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I did the K&N and charcoal delete on my 328i.

Could be placebo, but I did think my car felt a little stronger after the change. Again, could be wishful thinking

One thing, to this day, that is not placebo is the 1.5 hwy mpg improvement I now enjoy after the change.
So how do you exactly know you have improved 1.5 MPG on the highway? How have you tracked just your highway mileage MPG?

I keep exact records of all my cars MPG using a book and recording the miles driven and gallons for a complete fill up for every tank of gas (I completely fill the tank every time). I never saw any long term increase in overall average MPG in any car I used a K&N filter in.

There is no benefit to using a K&N. If a manufacturer could magically gain 1.5 MPG (and horsepower) on the highway rating for its cars using a less restrictive filter, it would use that filter as a production part and would make the cleaning of the filter as part of the scheduled maintenance program; especially BMW, which get constantly fined for not meeting U.S. CAFE requirements.
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      02-18-2012, 10:01 AM   #26
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The main benefit with going with a K&N filter (or similar) is the $$$$ Let me break it down for the deet-da-deets, You spend ($20) on oem, and replace it every 30,000 miles. Depending on your environment (dirty,sandy,dusty) you might/should replace at 15,000, So how many oem filter changes will you do? K&N for my 2011 335i is $54. So you tell me why after my free maintenance is up, why would I continue to pay ($20) for a filter when K&N will last a lifetime for only $54! Look at 98% of off road race trucks (including mine), they use K&N and have never have problem with foreign material ingestion.
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      02-18-2012, 10:31 AM   #27
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The main benefit with going with a K&N filter (or similar) is the $$$$ Let me break it down for the deet-da-deets, You spend ($20) on oem, and replace it every 30,000 miles. Depending on your environment (dirty,sandy,dusty) you might/should replace at 15,000, So how many oem filter changes will you do? K&N for my 2011 335i is $54. So you tell me why after my free maintenance is up, why would I continue to pay ($20) for a filter when K&N will last a lifetime for only $54! Look at 98% of off road race trucks (including mine), they use K&N and have never have problem with foreign material ingestion.
You make a good point. It still concerns me because of that charcoal filter. Did you remove that filter on your 335? Some people say delete it, others say don't. Some people say K&N is the way to go, some don't. I have had K&N's in every car I've had before my 328 and had no trouble. But when I posed the question to a BMW garage owner he all but had a coronary when I told him I put a K&N in my car. I've already returned it but I'm still not sure… maybe I should have kept it. There seems to be no real solid answer when it comes to this. I'm still researching….
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      02-18-2012, 10:56 AM   #28
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Originally Posted by tbracing View Post
The main benefit with going with a K&N filter (or similar) is the $$$$ Let me break it down for the deet-da-deets, You spend ($20) on oem, and replace it every 30,000 miles. Depending on your environment (dirty,sandy,dusty) you might/should replace at 15,000, So how many oem filter changes will you do? K&N for my 2011 335i is $54. So you tell me why after my free maintenance is up, why would I continue to pay ($20) for a filter when K&N will last a lifetime for only $54! Look at 98% of off road race trucks (including mine), they use K&N and have never have problem with foreign material ingestion.
Yeah, well maybe.

So the E9X calls for a filter change every third (BMW-schedule) oil change, so that's about every 45,000 - 50,000 miles. An OEM filter is $25 for a '06 325i from Tischer. A K&N filter is $50 from Turner Motorsport. So for the price of a K&N the average E90 owner can by two OEM filters and drive their car up to 150,000 miles (50K on the factory filter + 100,000 miles on the two replacements). I doubt many owners, even on this Forum, keep their cars past 150,000 (most think they blow up past the warranty period - LOL). K&N recommends cleaning the filter every 50,000 miles. The recharger kit costs $13. You may get 2 - 3 re-oilings with it, which is half the cost of a third OEM filter, which gets an owner to 200,000 miles (which hardly any one on the Forum will go with the same car). So I don't see any real savings. Throw in the chance of an owner over-oiling the filter when cleaning it and the possible damage to the intake sensors (and resultant repair) I see no real advantage to using one. And I say all of this from using K&N's since 1997 in five of my vehicles; all of which I converted back to paper.
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      02-18-2012, 10:59 AM   #29
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You make a good point. It still concerns me because of that charcoal filter. Did you remove that filter on your 335? Some people say delete it, others say don't. Some people say K&N is the way to go, some don't. I have had K&N's in every car I've had before my 328 and had no trouble. But when I posed the question to a BMW garage owner he all but had a coronary when I told him I put a K&N in my car. I've already returned it but I'm still not sure… maybe I should have kept it. There seems to be no real solid answer when it comes to this. I'm still researching….
I'm waiting for my free maintenance to expire, then I will.

My friend said to looking at this, I don't know if it applies specifically to your car. Also look at the link in the first post. http://www.e90post.com/forums/showthread.php?t=21590
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      02-19-2012, 10:30 AM   #30
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I'm waiting for my free maintenance to expire, then I will.

My friend said to looking at this, I don't know if it applies specifically to your car. Also look at the link in the first post. http://www.e90post.com/forums/showthread.php?t=21590
I too have free maintenance for another 4 years. I'll probably wait too. These directions are spot on as far as replacing the filter. I tried it using these steps and they're great. I book marked the directions.
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      02-19-2012, 11:46 AM   #31
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I too have free maintenance for another 4 years. I'll probably wait too. These directions are spot on as far as replacing the filter. I tried it using these steps and they're great. I book marked the directions.
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      02-19-2012, 07:26 PM   #32
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I put an K&N in my wifes 325Ci 6 years ago, have re oiled it twice and she has put about 70k miles on it. No problems, no worries, just clean environmentally friendly reuseable filter.

That said, anyone that is afraid of maintaining a filter or having a greater responsibility to their cars maintenance should just let a dealer or lube joint swap dry filters.

I have a K&N for my E90 LCI sitting in the box right now, and when I get done typing, I am going to drop it in the car.

What is the prospective gain of removing the charcoal filter other than airflow?
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      02-19-2012, 07:41 PM   #33
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I put an K&N in my wifes 325Ci 6 years ago, have re oiled it twice and she has put about 70k miles on it. No problems, no worries, just clean environmentally friendly reuseable filter.

That said, anyone that is afraid of maintaining a filter or having a greater responsibility to their cars maintenance should just let a dealer or lube joint swap dry filters.

I have a K&N for my E90 LCI sitting in the box right now, and when I get done typing, I am going to drop it in the car.

What is the prospective gain of removing the charcoal filter other than airflow?
I do like K&N filters. I've had them in all other cars I've owned. I may put it in eventually. As far as the removal of the charcoal filter, I'm assuming it's for better air flow. Several on this forum have done it and recommended it. I'm a bit apprehensive. I don't know if BMW is simply being over protective of their engine by putting it in and it's not really necessary or if the engine does in fact need that extra filtration.
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      02-20-2012, 09:56 AM   #34
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I do like K&N filters. I've had them in all other cars I've owned. I may put it in eventually. As far as the removal of the charcoal filter, I'm assuming it's for better air flow. Several on this forum have done it and recommended it. I'm a bit apprehensive. I don't know if BMW is simply being over protective of their engine by putting it in and it's not really necessary or if the engine does in fact need that extra filtration.
PERSONALLY, I couldn't tell a difference with the K&N OR the charcoal delete, It makes sense that more air flow would occur because the charcoal seems very restrictive, I just didnt notice anything. IMO im going with placebo affect, but thats been very debatable on here for awhile. Like I said just my opinion.
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      02-20-2012, 11:42 PM   #35
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WOW so let me get this straight, you have driven your car for 6k miles with the K&N filter and experienced no problems? Thanks for sharing. Well I don't know about anyone else, but that's good enough for me! I mean if that doesn't qualify as an engineering study I don't know what does. I mean heck, what's wrong with a little extra dirt getting into your engine, right! It certainly sounds like a worth while modification in order to get a little extra engine sound.
haha it really is for the engine sound; your MPG will be affected by how you drive!

IMO my car after 4500rpm is where you start to hear it but its still sounds stock; its just a tad bit louder and more pleasing to my ears

i took a iphone 4 video before and after off the roll.

Throttle response also went up a dat bit, but its still delayed in my opinion.

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      02-21-2012, 08:08 AM   #36
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WOW so let me get this straight, you have driven your car for 6k miles with the K&N filter and experienced no problems? Thanks for sharing. Well I don't know about anyone else, but that's good enough for me! I mean if that doesn't qualify as an engineering study I don't know what does. I mean heck, what's wrong with a little extra dirt getting into your engine, right! It certainly sounds like a worth while modification in order to get a little extra engine sound.
About as good as your engineering study that it allows more dirt into the engine? That is probably the oldest myth and the most laughable.

Bottom line, you simply cannot "feel" a difference of under 10whp when sitting in a car - just the facts of it. The only way to tell gains in that range is by actual testing.

That being said, I did a before/after dyno yesterday on my bone stock 08 335xi AT and saw zero noticeable gain from the K&N...there were slight gains of 2whp here/there but overall it was flat. I've had reusable filters on every vehicle I have owned for years and this is the first one where I didn't see an increase of at least 5whp.

I know a DCI would provide a definitive increase, but for personal reasons it wasn't the road I wanted to go.
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      02-21-2012, 09:31 AM   #37
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About as good as your engineering study that it allows more dirt into the engine? That is probably the oldest myth and the most laughable.

Bottom line, you simply cannot "feel" a difference of under 10whp when sitting in a car - just the facts of it. The only way to tell gains in that range is by actual testing.

That being said, I did a before/after dyno yesterday on my bone stock 08 335xi AT and saw zero noticeable gain from the K&N...there were slight gains of 2whp here/there but overall it was flat. I've had reusable filters on every vehicle I have owned for years and this is the first one where I didn't see an increase of at least 5whp.

I know a DCI would provide a definitive increase, but for personal reasons it wasn't the road I wanted to go.
The Spicer test a Myth? Really? You should really support that statement.

If you think a less restrictive filter (cone or otherwise) does not allow more dirt into your engine you need to put down the cool-aid. More air flow translates into less restriction. Basically, you have two factors when determining filter performance, filtration and dirt holding capacity. Filtration has several parts - pore size, porosity, depth, etc. Dirt holding capacity is largely a function of surface area of the filter.

K&N filters are very porous, with very poor control of the pore size. They will initially pass lots of air with low pressure drop, and assuming it is oiled properly will initially give good filtration, not as good as OEM though. The problem with them is that they have very little dirt holding capacity. They load up very quickly and then have higher pressure drop than OEM filters (i.e., pass less air at a given pressure drop).

Here is how one can uncover the lie about these so called performance filters.

Test your car with a new stock filter.
Next next test your car with no filter.

The delta between the two is the maximum theoretical gain any filter can provide - for most cars that is a 1% to 2% gain.

Last edited by cssnms; 02-21-2012 at 10:12 AM.
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      02-21-2012, 09:46 AM   #38
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Restriction has nothing to do with filtration. You can properly filter with a lower restriction when using a better material.

I fully understand dirt holding capacity - no one is stating not to properly maintain a reusable filter. But you're contradicting yourself - which is it, do they not filter as efficiently or do they load up with dirt?

No Kool-Aid here....just simple real world testing over the past 20 years. I've long given up attempting to argue with keyboard commandos - life is too short. If you're fine in your opinion that's great. Have a great day.
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      02-21-2012, 10:01 AM   #39
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Restriction has nothing to do with filtration. You can properly filter with a lower restriction when using a better material.

I fully understand dirt holding capacity - no one is stating not to properly maintain a reusable filter. But you're contradicting yourself - which is it, do they not filter as efficiently or do they load up with dirt?

No Kool-Aid here....just simple real world testing over the past 20 years. I've long given up attempting to argue with keyboard commandos - life is too short. If you're fine in your opinion that's great. Have a great day.
What would you recommend for good airflow and good dirt filtration? What do you use in your 335? I'm looking for the best option for my car.
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      02-21-2012, 10:12 AM   #40
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No Kool-Aid here....just simple real world testing over the past 20 years. I've long given up attempting to argue with keyboard commandos - life is too short. If you're fine in your opinion that's great. Have a great day.
My statements have nothing to do with opinion. Like I said, here is how one can uncover the lie about these so called "performance" filters.

Test your car on a dyno with a new stock filter.
Next test your car with no filter.

The delta between the two is the maximum theoretical gain any filter can provide - for most cars that is a 1% to 2% gain.
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      02-21-2012, 10:19 AM   #41
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The operative word, both times you have posted it, is MOST.

I have seen cars gain 15-20whp with a change, and that was not 1-2%. I do agree that most of their claims are inflated as are most aftermarket accessory companies.

While I would have preferred a nanofiber filter, unfortunately one doesn't exist. I could have created a DCI setup like this but again that wasn't what I wanted for this vehicle.
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      02-21-2012, 12:25 PM   #42
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I have seen cars gain 15-20whp with a change, and that was not 1-2%.
REALLY?! Please post up those independent dyno results for us all to see which filters provide a 15-20whp gain!
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      02-21-2012, 02:00 PM   #43
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You want me to post up dyno numbers from the past decade from a dyno I don't even operate any more??? Just so I can "convince" you? Sorry, you're not that important to me.

Believe it or not, even if someone disagrees with you - they may actually know what they're talking about.

Google is your friend - you claim you're smart enough, there's plenty of data out there if you open your eyes. The world doesn't revolve around this manufacturer.
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      02-21-2012, 02:08 PM   #44
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You want me to post up dyno numbers from the past decade from a dyno I don't even operate any more??? Just so I can "convince" you? Sorry, you're not that important to me.

Believe it or not, even if someone disagrees with you - they may actually know what they're talking about.

Google is your friend - you claim you're smart enough, there's plenty of data out there if you open your eyes. The world doesn't revolve around this manufacturer.
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