K&N Air Filters

[ALPHA]

I see that some of you changed their air filters...Will it actually help in the performance of the car ?? is it any better ?
I have a 3.0sd ... I am thinking of K&N ....

[Wagner]

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[ALPHA]

than you for the quick reply.... I will probably stick to the stock filter...
any more experience would be appreciated.

[Penguin]

If a K&N filter is oiled improperly (and some say even if oiled properly), it can mess-up the MAF sensor by depositing a thin film of oil on it. So under-oil it and it doesn't filter well, over-oil it and it will likely mess-up your MAF. You've got to get it "just right."

Frankly, if BMW though less air filter restriction would help performance they could have easily used a larger, less-restrictive paper filter to accomplish that end.

They did not.

Now, this is not directly related to the BMW auto engines, but...


K&N makes a filter for older BMW K bikes, making similar claims. A couple of guys put a K bike on a dyno and tested it three ways (a) stock paper filter, (b) stock paper filter with half of the filter blocked off, and (c) K&N filter.

Results?

Same HP for all three.


I don't think BMW engineers design their engines so that the air filter is the breathing bottleneck.

Now, if you start modifying the total airflow system, with things such as exhaust, intake manifold, etc., the air filter might become a limiting factor.

But I doubt that a simple air filter change to a K&N will do anything other than (a) take money out of your pocket, (b) increase maintenance, and (c) potentially mess-up your MAF.

Of course, that's only my opinion, and I an sure K&N and some others will disagree.

[nynd]

From the other site I am on (different carline) K&N don't seem to do much. Save your cash.

[C's Bimmer]

It doesn't make that much of a difference, but I've always been a huge fan of K&N. I would never do an intake, as the heat soak will actually cause you to lose power, rather than gain power, but swapping the filters can't hurt. Not to mention, they're fairly cheap.

[Penguin]

> swapping the filters can't hurt.

Oiled filters are known to frequently have issues with getting oil onto MAF sensors, particularly after re-oiling if a bit too much oil is used.

Obviously if a problem develops with the MAF, having a K&N on the engine has a good chance of being a warranty issue.

[C's Bimmer]

Originally Posted by Penguin

> swapping the filters can't hurt.

Oiled filters are known to frequently have issues with getting oil onto MAF sensors, particularly after re-oiling if a bit too much oil is used.

Obviously if a problem develops with the MAF, having a K&N on the engine has a good chance of being a warranty issue.

The MAF sensor issue was a common problem on older model BMW's, not on newer models. Most members of the M5Board are running BMC (that's a C, not a W) on their M's with no issues. Most of the E60.net members are running K&N's with no problems.

I have never had any issues on all my BMW's for the last 10 years and all had K&N's, except for my M5 which has BMC.

Furthermore, my dealer works on my BMW's with all my aftermarket parts. I've blown countless O2 sensors due to my exhaust system from headers back and they replace them. Clearly, that is not allowed, but they report my car as stock and do the job. I also have my suspension tuned and have blown some lower control arms due to the suspension. Once again, they fixed that with no problem and no questions. It depends on your dealer. The one in NY that I go to is one of the top in the country. they do this for many of their customers. If you're still worried though, K&N makes a dry filter that uses no oil.

[C's Bimmer]

Originally Posted by Penguin

Oiled filters are known to frequently have issues with getting oil onto MAF sensors, particularly after re-oiling if a bit too much oil is used.

Lastly, I will say this... I don't re-oil the K&N's. After they are pretty worked in, I toss them and buy new ones. They're cheap and the process of cleaning the old ones and re-oiling them doesn't make sense to me. For $50-$80, I'll just buy a new one.

[Hans_ACS]

Originally Posted by Penguin

If a K&N filter is oiled improperly (and some say even if oiled properly), it can mess-up the MAF sensor by depositing a thin film of oil on it. So under-oil it and it doesn't filter well, over-oil it and it will likely mess-up your MAF. You've got to get it "just right."

Frankly, if BMW though less air filter restriction would help performance they could have easily used a larger, less-restrictive paper filter to accomplish that end.

They did not.

Now, this is not directly related to the BMW auto engines, but...


K&N makes a filter for older BMW K bikes, making similar claims. A couple of guys put a K bike on a dyno and tested it three ways (a) stock paper filter, (b) stock paper filter with half of the filter blocked off, and (c) K&N filter.

Results?

Same HP for all three.


I don't think BMW engineers design their engines so that the air filter is the breathing bottleneck.

Now, if you start modifying the total airflow system, with things such as exhaust, intake manifold, etc., the air filter might become a limiting factor.

But I doubt that a simple air filter change to a K&N will do anything other than (a) take money out of your pocket, (b) increase maintenance, and (c) potentially mess-up your MAF.

Of course, that's only my opinion, and I an sure K&N and some others will disagree.

This info is correct. Besides, assume it adds 3hp, you will NOT feel the difference. Also the sound is left unchanged. Bottomline, the only thing that is changed is the amount of money in your pocket