Rick Lee

I know there's huge debate on this with earlier 911's, but have not seen much on it with 993's. Yes, I did a search and found a lot of stuff on hot air with cone set-ups, CEL's and filter disintegration.

But which offers the best protection without a decrease in performance? My car came with a K&N filter (non-cone style). I've cleaned and re-oiled it once. Just did it again last week and was dissatisfied with the cleaning. So I did not reinstall. It just didn't look clean enough after following the directions twice. So I bought an OEM Mahle filter yesterday. Now I just want to hear what everyone thinks about one vs. the other.

Mark in Baltimore

I ran a K&N filter in my original VW GTI back in the 80's, had a cone-style filter on my Pathfinder in the mid-90's and briefly tried it on my recently sold 4Runner. On the Pathfinder, the cone filter made the engine sound better, and I thought I could detect better performance. However, after reading on the internet about the dubious benefits and possibly compromised air cleaning abilities of the oil and mesh system, I decided to leave the stock paper filters in my 993 and Sequoia. Traditionally, I have never kept cars for longer than three years, so I have no idea whether the K&N system was detrimental to long-term engine health.

I'd say use the stock filter and try and find your performence elsewhere.

akolodesh

Rick, I tried to run the evo cone filter on my OBDII and was getting consistent o2 cel's. When I spoke to Steve Weiner, he highly recommended against running the cones on OBDII's (has to do with the positions of the sensors and the inability for the ecu to adjust accordingly). There is no problem running a cone on OBDI (my mechanic has ran one on his '95 c2 for years with no problems). From a sound perspective, the cones do sound incredible though.

Rick Lee

My K&N is the same shape at the stock filter. I have the stock airbox, albeit a drilled-out lid. I won't put a cone set-up on there, though I wouldn't mind having the extra space.

STLPCA

From: This aftermarket filter thread.

jdoc7

I sold my K&N because it was too thick and did not fit well. When you clamp down on the airbox, it is way too tight. I'm afraid that overtime with the high temps in the engine bay, the airbox clamps will break off. This happened to 2 944 Turbos I had. So, I'm back to the original Mahles and they work just like the factory intended them to.

delanobe

I got a K&N and it fits perfectly?

Maybe it has something to do that I have the motorsound option?

Brett - 1996 C4

Didn't K&N take their airbox-shaped filter off the market because the gasket could crumble off and get sucked into the engine? Or are they back on the market?

I just stick a new Mahle in every year and don't worry about it.

sptschoice

I used the K & N cone filter and love the engine sound at high revs

jdoc7

The K&N Filters are still on the market. I also remember complaints about the gasket flaking off. I did notice parts of my gasket were damaged after installation due to the fact that it was such a tight fit. Clamping down on the gasket may have damaged it, I don't know. I'd stick with the Mahle's since you will not gain a thing in performance on a street car other than a different sound.

STLPCA

K&N for 993s was off the market to correct the gasket disintegration problem. AFAIK that's been fixed & they are again available.