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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N20, N26, B46, B48 Turbo Engine / Drivetrain / Exhaust Modifications > Are air filters worth it?
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      01-01-2016, 08:57 PM   #1
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Are air filters worth it?

I've heard about people putting these K&N air filters in their cars, but do they actually make a difference at all in performance or sound?

Here is the one made for my car: http://www.knfilters.com/search/prod...x?prod=33-2990
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      01-01-2016, 09:06 PM   #2

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Originally Posted by EB F32 View Post
I've heard about people putting these K&N air filters in their cars, but do they actually make a difference at all in performance or sound?

Here is the one made for my car: http://www.knfilters.com/search/prod...x?prod=33-2990
The best filter is no filter because it has the least amount of airflow obstruction.
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      01-01-2016, 09:13 PM   #3
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Performance, I doubt it, not enough for you to tell the difference. Sound, sure, more thoarty. Whats for sure is you will attract more gunk and get an oily throttle body from the oil element you put on your KN, may screw up your MAP sensor. I'll pass.
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      01-02-2016, 09:23 AM   #4
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aFe makes a dry free flow drop in filter no need to worry about oil on the MAF.


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      01-04-2016, 10:20 AM   #5

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I truly believe for this n20 platform the stock paper filter is fine, its cheap, just put a new one in every oil change if u want. I spent 60$ and ordered an afe dry for the f30, the throttle input seemed to suck, it was laggy and the car seemed to almost surge a little, i used it for 2 days and took it out and replaced for a stock paper. Stock paper felt better. Ill sell the afe if anyone wants it, less then 100 miles
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      01-04-2016, 03:46 PM   #6
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Better sound
more air
Performance doubt you will notice any difference

Get the K&N, it is cheap and high quality
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      01-16-2016, 08:38 PM   #7
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ok here is the poop on air intake filters.. a motor is just a big pump, air in air out, so the aftermarket air intake market is the more air in the better the performance. Well that is true, only if you can get that extra air out. So will adding just a afe cold air intake make a difference, like they claim up to 7 horsepower, It just may, if you add the $3k akropovic exhaust, now the motor has lots of clean unrestricted air in and it can get all that extra hot exhaust out.. So now you say restricted??? Well now we have another great invention, a free flow exhaust port. or a header, now these allow the hot gasses to exit the motor faster thus getting rid of the heat better, and heat is our enemy here boys.. Now we have our $500 afe cold air intake, $3k exhust, and $500 header,, NOW ask me if you notice a difference.. This should be your first mod for more horsepower as now you have a much much more efficient pump, So add all the aftermarket horse power add ons now as you know no matter what you due, the motor is able to breath a lot better.
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      01-25-2016, 08:53 PM   #8
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That's only partially true assuming the stock exhaust was at it's limits of flow.

More times then not, the drop in filters free up HP compared to stock paper filters on any car.

Is it noticeable, not to some people.

The real power is upping the boost with a tune.

Then after that you will usually want to cool things off with an intercooler but get the throughput by reducing the biggest restriction, the cat.

In the quest for more power on this car, start with a tune. Easy, simple, relatively good value and obvious gains.
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      02-02-2016, 07:22 PM   #9
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Have been using K&N filters on all my rides when it is available. If you pay attention to how your car feels before and after, I think can feel the subtle difference.
I swapped and try BMC drop in filter and my F30 was not as responsive moving off from idle and once I swapped back, the responsiveness came back. I attributed that to the K&N fitment which is perfect versus the BMC which was very tight fit and hard to clamp down the cover. Since it breathes better, I also have the Bastuck exhaust to remove the "constipation"!

It is cheap and you can clean it and reused. From my estimate, it is 2-3x more than stock filters so it would have paid for itself soon enough.

On my F30, I had it since day 1 and it is 31k km now. On my Honda Odyssey, it is already 6+years and 170k km. I don't have any issues mentioned here.
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      02-03-2016, 09:23 AM   #10
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I put a Afe Power oiled drop-in filter in mine a week ago. There is no difference what so ever.

Only worried about MAF sensor getting fucked with oil now. Didn't mention anything about that on the sellers description.
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      02-03-2016, 01:06 PM   #11
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I replaced mine with a KN filter- my Booty Dyno felt better response to acceleration. (but I'm sure it was psychological. KN is best)

I just upgraded to an AFE 5r intake so if you want to buy my used KN filter let me know. I bought it in December.
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      04-21-2016, 09:54 PM   #12
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k&n makes a noticeable difference in sound and the gears are usually changing smoother vs stock air filter.
For $40-$50 (vs $20-$25 stock) and the possibility of cleaning it for $10 with lifetime warranty it's a good upgrade if you are going to keep the car for a long time.
An odd thing i found is that on my previous n54 engine the oil temperature was about 5-10% hotter with k&n than with the stock. On my other previous cars it did not happen.
Also on the n20 or n26 engines (same as on e46) there is a second non-removable air filter so you don't have to worry about the oil getting on maf sensor.
A good practice is to get the k&n filter out the plastic bag and let the oil from it drip overnight and clean the excess of oil from rubber housing with a microfiber cloth
On my previous e90 n52 it threw an error after installing k&n. I removed the maff sensor and cleaned it special cleaner from o'reilly ($5-$7) It was all good after that.
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      04-22-2016, 06:36 AM   #13
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Carby cleaner is all you need. I've Used K&N on most, if not all my cars over the last twenty years.(v8's, turbos etc) No issues. The one car that was sensitive to oil on the AFM was my old late 90's WRX. I just very lightly oiled it. Hold the factory air filter and a K&N against the light/sun and you'll see why they flow considerably more. Turbo cars suck a lot of air. Up the boost with a tune from the factory 17psi to 20+psi and I think it will useful - especially once the blockage at the other end is removed (cat). Hence why stage 2 tune minus cat and air filter really wake up these cars (...funnily enough just like every other turbo car....)
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