[SC11]

Is a drop in air filter like K&N worth it on a stock M40i?

[X5MSD]

Yes
I have done this mod today
Really pleased with the results
Check out the std bmw filter vs the K&N

[SC11]

Originally Posted by X5MSD

Yes
I have done this mod today
Really pleased with the results
Check out the std bmw filter vs the K&N

Any noticeable different in response or noise?

[X5MSD]

Slight sound difference
Throttle response is better
And you can hear the turbos spin
Loving it
Don't forget to pop your fuse out for more sound

[SC11]

Originally Posted by X5MSD

Slight sound difference
Throttle response is better
And you can hear the turbos spin
Loving it
Don't forget to pop your fuse out for more sound

Did you do a video in the end?

And already coded ‘ASD off’ and ‘start in Sports Ind’

[X5MSD]

I did mate
Not sure how to get it on here
You can't really hear much
When stationary
When driving you can hear the turbos
(Didn't have a passenger who could have filmed)

[X5MSD]

Originally Posted by PureModelsOnly

Have fun ruining your MAF from over oiling the filter. If you really must put the K&N sticker on the car but leave the filter alone.

The filter is pre oiled
Ready to go,wasn't oily when I touched it
Why would it damage the MAF ?

[MechX3M40i]

I have a strong suspicion that this could be an excuse from car manufacturers to refuse warranty repair since the cars had been 'mod' by unauthorized parts.

I've used oiled air filters for many years in several Japanese cars/SUV and none had any sensor failure ever. I put well over 200k miles in a Nissan Maxima before half giving it away to a colleague who needed to get a car for his aging mom going to church. Disclaimer: I have to say though I have no specific experience with the K and N brand so I can't extend my experience there.

[X5MSD]

Would this also apply in cone filters ?

[AnOldBiker]

I've had the K&N and friends had same of other companies. My K&N was pre oiled from the manufacture and same with the others. It was on my Dodge with the cummins engine.

After 15k, I pulled the filter, and the air tube from the filter box to the turbo as recommended by my friend.

The oil was on the MAF, in the tube and on the turbo blades. Not much, but started to collect. If enough collected, it can throw off the balance of the blades, destroying the turbo.

The filter worked good, but if the blades are not checked constantly, you could loose the turbo.

I prefer the aFe dry now. My oiled filter went to the dump.

[fricfracfrank]

I had a K&N filter in my Volvo s60r years ago and did hear a very very slight difference in sound.

With that being said though I remember it being oily and since I was pretty uneducated and naive about the subject I didn't think twice about installing it.

At this point IF I were to put a pre/oiled filter in I would hit it with compressed air to remove as much excess oil as possible.

To each their own

[GT500R]

Originally Posted by AnOldBiker

I've had the K&N and friends had same of other companies. My K&N was pre oiled from the manufacture and same with the others. It was on my Dodge with the cummins engine.

After 15k, I pulled the filter, and the air tube from the filter box to the turbo as recommended by my friend.

The oil was on the MAF, in the tube and on the turbo blades. Not much, but started to collect. If enough collected, it can throw off the balance of the blades, destroying the turbo.

The filter worked good, but if the blades are not checked constantly, you could loose the turbo.

I prefer the aFe dry now. My oiled filter went to the dump.

I have been looking for dry filters and only found Arma Speed.

Have you found others for X3 M40i?

[verysideways]

Yup, lots of things to watch for here.
1) BMW have refused to cover an engine failure on an M3 CP in the UK because of an aftermarket filter, which they said could have contributed to the engine failure. So yes, it does affect your warranty.
2) Oiled filters like the K&N do affect your MAF and will cause the MAF to fail earlier than it would otherwise. Maybe much earlier, maybe not that much earlier, but it will.
3) The stock air filter is every bit as good at allowing air through as a K&N. I have seen dyno results on multiple cars which prove this. The problem is that the stock air filter is replaced too infrequently. I believe it's every 3rd oil service, which is 60k miles or so? For the sake of £20, just replace the stock air filter at EVERY oil service. Maximum airflow, no warranty issues.

Look at the surface area provided by the stock airfilter - it's massive! It's very efficient WHEN IT'S CLEAN. Just replace it more often. It's cheap.

[Tchgrif]

all three of our vehicles have K&N air filters on them and I have always used them as did my grandfather, a mechanical engineer. Every forum has people who are quick to harp on the myth that oiled air filters damage engines but this is not only not proven it's dis-proven. mythology is a difficult human condition and it's virtually impossible to undo it. we once believed that clabbered milk was a sign of witchcraft, luckily we outgrew that one.......well most of us did! but this air filter one might hang on as long as blind faith on an invisible wizard in the sky.

[AnOldBiker]

I have always considered ease of maintenance for trips since I enjoy traveling. The BMW I have has a filter design that is fairly new, and trying to find a replacement on the road is extremely hard .... as with finding a dealership while traveling. When asking my local dealership, they said they can order one and be there in 2 days. None in stock .. more time in a hotel waiting for a part ?

The dry, reusable replacements are easy to clean while in the middle of now where traveling between point a and point b, allowing me to clean and replace if needed. If you only stay in towing distance from a dealer, keeping stock is fine. Just not for me as of yet.

[fsugatorbait]

I put about 100k miles on my old 335 with a K&N filter cleaned/re-oiled every 10k miles and I had no issues. I would also use a MAF cleaner for the sensor each time the filter was cleaned. Entire process took less than 20 min including drying time.

[skier219]

Originally Posted by PureModelsOnly

Do people think car manufacturers put in purposefully restrictive air filters or something and dropping in a $40 aftermarket filter is going to magically unlock some hidden potential in the engine?

This is the reality of it. Any true gains would really need to be accompanied by tuning changes to really matter.

But hey, you got to admire K&N's business model for separating people and their money, it's very effective!

[i4M50Guy]

I run an AFE Dry on my M140i. Waiting on them bringing out one for the X3 M40i and I'll get one fitted in that too!

[sinbad4]

I've used K&N filters for nearly 25 years. Love them, never an issue. Does make a noticeable difference in the M40i.

[ParadigmDawg]

Here is the thing, a drop-in filter(especially if it is oiled) can cause a voided warranty.

The gain you may see would be very small and likely not noticeable in true times or power gains. So only the owner can decide if it is worth the risk.

For reference, my M40 ran better 0-60 times via Dragy with stock air box/filter vs a K&N drop-in or a BMS cold intake system. Of course, it sounded better with the K&N and best with the BMS.

[X3emist]

My take is that, yes, you might get an audible benefit. But, to make power you have to flow more air through your engine. Therefore one would need a less restricted exhaust system along WITH a better air filter. But, to each his own.

[X5MSD]

Ive listened to other members
And have now removed it from my car
Don't want a knackered engine