Cal Club Autocross Forums

I'm going to be changing my air filter to a non-OEM model shortly (been on bumper-to-bumper care until now). I'm strongly considering a K&N reusable filter, but I noticed that it requires oil after cleaning. After doing some research, it looks like most aftermarket performance filters use oil as well. I've heard that the oil can make it's way into the intake and get into the valves/cylinders and cause carbon buildup. If that's the case, it'd be even more of a problem for me, since my engine is direct injection and you can't use gas-bourne detergents to clean the valves. Anyone have any insights? Is this just a nasty rumor?

One must be very judicious adding the oil. It's easy to over do it, but since it's dyed red, it's easy to use. After you clean the filter with their cleaner and let it dry, it will be white. You put a little of the oil on and let it spread out. You can see if there is any white left and add a tiny bit more where needed.

You would have to put an awful lot on to create the "damage" that you mention. The first thing that can be effected by oil coming off of the filter is the mass air flow metering element. There is a spray that you can buy to blast it clean if necessary.

I have two things for you to consider:
1) OE type paper filters don't present much of a restriction.
2) K&N type oiled fiber filters don't filter as well as paper.

John Stimson wrote:I have two things for you to consider:
1) OE type paper filters don't present much of a restriction.
2) K&N type oiled fiber filters don't filter as well as paper.

Good info. Thanks, John.

John Stimson wrote:I have two things for you to consider:
1) OE type paper filters don't present much of a restriction.
2) K&N type oiled fiber filters don't filter as well as paper.

Yeah oiled filters suck. He should run two paper filters for extra protection. }:)

Cant find the PDF, but we tested these back-to-back-to-back on the dyno (same day, multiple runs, with repeats) in our RX-8.

A dirty K&N, full season of use made the least power. We would have liked to clean and retest it, but it could not be done in the confines of the time allotted, which is why we brought a brand new one as well.
Brand new out of the box Mazda (OE paper) filter made 2hp (peak) more than the dirty K&N, with the same Tq.
Brand new out of the box K&N made 5hp and 2tq more than the dirty K&N.
Brand new out of the box Green filter made 7hp and 2tq more than the dirty K&N.

These numbers are on a dynojet, at the wheels.

Call C2 and order a Green.

Kurt Rahn wrote:I'm going to be changing my air filter to a non-OEM model shortly (been on bumper-to-bumper care until now). I'm strongly considering a K&N reusable filter, but I noticed that it requires oil after cleaning. After doing some research, it looks like most aftermarket performance filters use oil as well. I've heard that the oil can make it's way into the intake and get into the valves/cylinders and cause carbon buildup. If that's the case, it'd be even more of a problem for me, since my engine is direct injection and you can't use gas-bourne detergents to clean the valves. Anyone have any insights? Is this just a nasty rumor?

Its not that it'll make its way into the engine but that it'll contaminate the MAF sensor and mess up the readings or cause CEL. Look around on the Mustang and Camaro forums its apparently a problem when to much oil is reapplied when cleaning, I never had an issue but I followed the instructions pretty well.
FWIW I made 5 more hp in my Mustang going to a K&N, never tried a green, but I've head they don't filter very well so more frequent oil changes will probably be required.

If there is oil dripping off of the filter after you service it you may have used to much. I always clean the MAF when I am servicing the filter. Never had a CEL light from a filter change, and had lots of trouble free miles on our RX-8 with the Green installed. I cant think of a car I have owned that did not have a K&N or Green filter installed - including our 2001 Expedition that has had one of these types of filters installed for about 190,000 of its 204,000 mile life so far.

Kurt, your turbo will push as much air as the engine is asking for under normal conditions. The HP gains that people are reporting with NA engines will equate to maybe quicker spool times under initial throttle. How much quicker? Probably not very much.

IMO, stay with paper. Just make sure to change it often enough. The other thing extra restriction does is push your turbo higher on the compressor map, which at full power will mean less efficiency and a hotter charge.

Davin Swanson wrote:Kurt, your turbo will push as much air as the engine is asking for under normal conditions. The HP gains that people are reporting with NA engines will equate to maybe quicker spool times under initial throttle. How much quicker? Probably not very much.

IMO, stay with paper. Just make sure to change it often enough. The other thing extra restriction does is push your turbo higher on the compressor map, which at full power will mean less efficiency and a hotter charge.

I knew it, I knew it. You've been cheating in SK2! Come on Big Boy, where you hiding that turbo...under your seat?

Ed Holley wrote:

Davin Swanson wrote:Kurt, your turbo will push as much air as the engine is asking for under normal conditions. The HP gains that people are reporting with NA engines will equate to maybe quicker spool times under initial throttle. How much quicker? Probably not very much.

IMO, stay with paper. Just make sure to change it often enough. The other thing extra restriction does is push your turbo higher on the compressor map, which at full power will mean less efficiency and a hotter charge.

I knew it, I knew it. You've been cheating in SK2! Come on Big Boy, where you hiding that turbo...under your seat?

It's all residual knowledge from my days of turbo diesel VWs. I swear!

Jason Isley BS RX8 wrote:

John Stimson wrote:I have two things for you to consider:
1) OE type paper filters don't present much of a restriction.
2) K&N type oiled fiber filters don't filter as well as paper.

Yeah oiled filters suck. He should run two paper filters for extra protection. }:)

Cant find the PDF, but we tested these back-to-back-to-back on the dyno (same day, multiple runs, with repeats) in our RX-8.

A dirty K&N, full season of use made the least power. We would have liked to clean and retest it, but it could not be done in the confines of the time allotted, which is why we brought a brand new one as well.
Brand new out of the box Mazda (OE paper) filter made 2hp (peak) more than the dirty K&N, with the same Tq.
Brand new out of the box K&N made 5hp and 2tq more than the dirty K&N.
Brand new out of the box Green filter made 7hp and 2tq more than the dirty K&N.

These numbers are on a dynojet, at the wheels.

Call C2 and order a Green.

That's what I'm talkin' 'bout! Thanks, Jason!

Jason Isley BS RX8 wrote:

John Stimson wrote:I have two things for you to consider:
1) OE type paper filters don't present much of a restriction.
2) K&N type oiled fiber filters don't filter as well as paper.

Yeah oiled filters suck. He should run two paper filters for extra protection. }:)

Cant find the PDF, but we tested these back-to-back-to-back on the dyno (same day, multiple runs, with repeats) in our RX-8.

A dirty K&N, full season of use made the least power. We would have liked to clean and retest it, but it could not be done in the confines of the time allotted, which is why we brought a brand new one as well.
Brand new out of the box Mazda (OE paper) filter made 2hp (peak) more than the dirty K&N, with the same Tq.
Brand new out of the box K&N made 5hp and 2tq more than the dirty K&N.
Brand new out of the box Green filter made 7hp and 2tq more than the dirty K&N.

These numbers are on a dynojet, at the wheels.

Call C2 and order a Green.

+1
After Jason did that testing, I saw a demo at SEMA where the Green Filter out flowed K&N. Better flow may = less filtering, but I've been running a Green Filter ever since.

...how much more front wheel spin are you looking for Kurt?

Marshall Grice wrote:...how much more front wheel spin are you looking for Kurt?

Richard Jung wrote:

Jason Isley BS RX8 wrote:Call C2 and order a Green.

+1
After Jason did that testing, I saw a demo at SEMA where the Green Filter out flowed K&N. Better flow may = less filtering, but I've been running a Green Filter ever since.

Sadly, it looks like Green doesn't offer a filter for the Mini. K&N it is...

Marshall Grice wrote:...how much more front wheel spin are you looking for Kurt?

What can I say? I like tire smoke!