Washable filters

[mdem]

K&N brand has washable air filters and cabin filters that they claim will last the life of the vehicle. Has anyone used these and if so, what are your opinions?

[Deleted User 732]

I had used them in an AustinMaestro, MG Maestro 2.0 Efi, several Metros, Rover 214 and Rover 400 and a "Green Filter" (as K&N didn't make one for my Rover V6 45). They are OK and the only one where I can actually see a test result was for my MG Maestro. A mag tested the oringinal filter with a Pipercross and K&N. From memory the original gave 108 bhp, the Pipercross gave 102 bhp and the K&N gave 112 bhp. There was no significant power increase note by either the testers or myself. I just liked the idea of buy one and service it regulary to have a clean breathing engine. Those days they were under £20 but now, for the XE, £69. That is just far too much, for any returns of just a few bhp increase and no fuel saving benefits to notice. There was a recent TV prog on our TV stations that a Nissan 240Z was fitted with a K&N filter and a wide bore exhaust and the bhp dropped by nearly 20 from what it should have been. The ECU was reprogrammed and the engine then gave out 20bhp above standard. Without a remap I would now save the cash and buy fuel.

[RoJo]

My understanding is that K&N type filters don't filter as effectively as OE filters and you're probably better off replacing OE filter more often.

[RalphieM]

There is also something else to consider !
Modern cars are far more critical when it comes to aftermarket air filters and the like, especially where K&N's are concerned.
A K&N is oiled and as such a very fine mist is drawn off the filter and onto the MAF (mass airflow meter) which can (and does) cause some very poor running issues.
Certain cars are more prone to this than others, in the good old days when I was tuning and racing Imprezas they would barely run with a K&N and if they did it was not long before the MAF was fooked, they would run perfectly on a Pipercross though ?
Mitsubishi Evo's however would run absolutely fine on a K&N !!

[Deleted User 732]

Good points.

[ChrisGB]

If you are just replacing a panel filter, I don't think it is worth the reduced filtration unless you have proven the filter to be restrictive. Also, unless you are racing, doing anything that yields less than a 20% increase is not very noticeable.

Aftermarket inlet systems often mess with the way the airflow interacts with the MAF, so unless you are re-calibrating the ECU, generally not worth the effort.

When it comes to modification, go large or go home!

[Deleted User 732]

I think that they are a waste of money at today's prices. When I bought them they were about the cost of 3 paper ones so saved cash as I kept my cars a few years if I liked them and the Rover metro, 214 and 400 took the same filter. The MG and Austin Maestro had the same filter so I only actually bout two over several cars. The 45V^ had a Green filter but that was only £30 and stayed in the car for 9 years so owed me nothing. If anyone wants the K&N or Green filter for similar cars they can have them for the postage costs.

[BOBCDP]

Hmmmmm, the posts above have made me think. Did I do the wrong thing? I bought a K & N almost 12 months ago thinking that as I had no intention of selling the car, it might be a good idea to get a longlife filter. My experience so far has been that there have been no problems at all and neither have I noticed the slightest difference as far performance is concerned but then I didn't really expect to notice a difference. Not sure about oil mist affecting the MAF though. I bow to greater knowledge and experience in these matters but from what I could see when I handled the filter before I fitted it, it didn't look or feel very oily to me and I think there would have to be a hell of a gale blowing up the inlet to create any sort of mist.

[RalphieM]

The mist is in such small quantities that you would not be able to find or feel it on any part of the intake system upstream of the filter.
However most MAF sensors consist of a heated wire that actually cooks the oil misting once it has settled on it thus causing poor running as the air flow readings all go to pot.
There is a "hell of a gale" blowing up the inlet, that is the whole idea of a forced induction engine.
As I said, not all cars will suffer these problems as not all MAF sensors are as sensitive but over a 10 year period I saw enough seriously damaged engines to convince me never to fit ANY oiled filter, be it panel or induction cone.

[BOBCDP]

The mist is in such small quantities that you would not be able to find or feel it on any part of the intake system upstream of the filter.
However most MAF sensors consist of a heated wire that actually cooks the oil misting once it has settled on it thus causing poor running as the air flow readings all go to pot.
There is a "hell of a gale" blowing up the inlet, that is the whole idea of a forced induction engine.
As I said, not all cars will suffer these problems as not all MAF sensors are as sensitive but over a 10 year period I saw enough seriously damaged engines to convince me never to fit ANY oiled filter, be it panel or induction cone.

Thanks for that detailed explanation. You have convinced me that even though I haven’t had a problem up to now, I would have to clean the K & N and re oil it anyway and it’s not worth taking a chance so I will be going back to the standard paper version.