Air filters ..... the reality.

[mcbeee]

I saw a couple of posts where people were putting in K&N filters etc and thought I'd put in my two cents worth.
I used K&N (used them for many years, not dissing them, they do work) and stopped after reading a rather long study by an independent researcher on the various air filters and the amount of particulates that enter the engine. It was quite a surprise!
I was using one in my Silverado pickup truck and I had noticed a very slight improvement in fuel economy and a nicer sound when stepping on the accelerator, had the same effect in my previous vehicles as well.... but and it's a big but, the amount of "crap" that passed through the filter was a lot more than other filters. The researcher tested a lot of different brands , OEM's and aftermarket performance models and it really surprised me to find that the GM filter (OEM) was far superior to the current filter I was using. After a painful minute or two while the last two functioning brain cells went to work I figured out the cost of engine repairs vs. a slight increase in mileage, plus a vroom sound didn't add up well. It made no sense to keep using the expensive aftermarket HP filter. Granted, it was reuseable but twenty or thirty dollars doesn't go far when you have to repair an engine.

I'm going to look for the report I read and post it if I can find it.

 

[Bumpy]

I thought the air was pure on Vancouver Island ?
I have similar experience with K&N and never felt 100% confident with recharging them. How much oil was enough and I probably used too much.
With my Zed I discovered 2 things:
1: Stock air and intake is about as good as it gets unless you are tuning for track use.
2: Oil residue from 'wet' air filtres can compromise the sensors down wind.

So I opted to stick with stock.

Bumpy

PS On my 08 3.0SI Air Filtre housing there appears to be a permanent carbon filtre in the top housing in addition to the regular air filtre.

 

[mcbeee]

I thought the air was pure on Vancouver Island ?

I lived in Alberta for 47 years before moving here in 2014. This is "retirement central". Not driving on any gravel roads anymore.


PS: I put a Dinan cold air intake on my second Z3, it helped a little. Kept the stock filter.

 

[Mike6]

K&N filters and a few other similar manufacturers often state the performance increase you get through allowing extra air to reach the engine as the selling point. This is usually a lot of bull unless you make significant other changes to the engine setup. What you do get is an increase in induction noise which makes you think the car is much faster, in reality you could be losing performance. With the K&Ns you have to clean them from time to time and then spray on an oil. I have read reports with the Zed that over enthusiastic application of the oil can mean that this reaches the MAF which results in an oddly running engine and error codes. It takes only a few minutes to change the filter and they are cheap so buy a good one and change regularly.

 

[buzyg]

Interesting to read. OEM it is then.

 

[Ewazix]

In the 'old days' I used aftermarket filters on old carburetor set-ups because you could easily re-jet and gain a couple of bhp with better intake noise. On modern mapped systems there really aren't any gains to be made unless you go for a full cold-air intake and re-map to utilise the upgrade. One proper test outed K&N's which quickly deteriorated and was worse than stock and tests have shown that stock systems have plenty of excess capacity designed in to allow for clogging between services so air flow is not a power restriction issue with regular changes anyway.

http://www.nicoclub.com/archives/kn-vs-oem-filter.html

Conclusion from the test said "the K&N 'plugged up' nearly 3 times faster, passed 18 times more dirt and captured 37% less dirt"

 

[Machine monkey]

I agree if your car is a standard car stick to the system BMW supplies. I put a K&N on mine no gains what so ever. I will be using it again now as my intake is now in the boot!