RG5

My '85 Carrera has a custom exhaust/header setup and I was thinking of complimenting that with an aftermarket airfilter. I was just thinking what are some recommendations for air filters. I think I would probably retain the factory airbox, so one immediate option is to replace the factory paper filter with an equivalent size K&N filter.

Any advice welcome.

Richard

Dan Cobb

IIRC, studies have shown that K&N filters do not provide a significant increase in air flow over the stock filter element. The best thing you can do IMO is to ensure that you are running a clean, stock filter.
I fell for the cone filter setup only to grow wiser (albeit a bit poorer!) after only a couple hundred miles.
If you really think you need additional air flow, then do a search here and on the Pelican site for some pics of modified air boxes. Some cut/drill holes in them in order to decrease restriction of incoming air. I suspect that this would help if the added air flow consisted of cool air rather than air already warmed up by passing over the engine to the front of the engine bay. All-in-All, I believe this factor negates the increased air flow, thus being a fairly unnecessary modification.
JMO
+++

Steve Weiner-Rennsport Systems

Hi Richard:

As Dan said (above), the K&N cone filters make noise at the expense of power and the factory Porsche airbox is VERY well designed.

If you want some additional noise, you'll do no harm to the performance if you add some holes to the stock aircleaner cover. Modified engines do respond to this modification however stock 3.2's barely change. There is no hot air in the engine compartment when the car is moving at speed as the cooling fan is pulling a LOT of air in there.

K&N filters (panel type) are fine for race cars where maximum engine life is not expected but I'd recommend sticking with the OEM paper filters for any street usage.

RG5

Thanks Steve,

The one thing I don't want is more noise. With the exhaust/header mod the car is loud enought already!

Cheers

Richard.

JJ 88 Cab

Hi Richard -

just to add another voice in agreement with the above comments, I have seen where the K&N will allow a small amount of additional airflow, but nothing significant. Also I would be concerned that if a filter is allowing much additional air into the engine, it may not be filtering it properly. The last thing I'd want is dirty air getting in.

Jay Jagolta
88 911 Cab
84 BMW 533i

Jay Gratton

I had a K&N come with my '85 and I notice no difference. I haven't changed it, but I probably will in the future. The way I look at it is that Porsche did it for a reason, and if it is good enough for Porsche then it is good enough for me. I would stick with the OEM filter. Best wishes - Jay

Peter Zimmermann

Richard: I tried a K&N filter in my PCA Club Racer ('81 SC), and I have to echo the above comments. There was no difference in my car's performance, and I went back to using o.e. filters.
Pete

Chuck Harmon

I did the before and after dyno with K&N Vs. Stock paper... I got 7 Hp out of the K&N on my 1983 SC. I use K&N
I also check my air box now and then for dirt... it is always very clean !

recordmanv

I have an 83 SC and it makes a huge difference in low end torque and throttle response. I don't know about the results with a factory tuned SC. My SC is a bone stock engine, but has a bypass pipe with factory muffler and a very aggressive air/fuel mixture with advanced timing......I didn't really know the difference until my mechanic replaced my filter with an OEM. My wrench thought the K and N should be white-hence he thought it was really dirty and replaced it. I could tell the instant I accelerated in first gear! Pulled over and changed the filters. Huge difference. I swear by it. OEM filter seems to add throttle latency and the car just dogged until it hits about 4k and then it launches like a turbo kicked in or something. The K and N gives instant response with a smoother and stronger pull. I know this isn't science, but the results were not "kinda" but very obvious. I agree with Chuck, dirt is not an issue, even after autocrossing in dusty areas. Maybe it's an SC thing? If you don't drive aggressive, then don't bother. If you drive it hard like me, the extra power becomes very apparent with K and N. To each his own. FWIW, adding holes in a CIS SC box didn't add any power that I could feel, but it sure sounds like a monster under full throttle!

Noel

As Steve mentioned above. OEM is the way to go. There have been tests done at the dyno and no addional power has been measured from using a K&N. In fact, I remember reading an article about an SC being run with out any airfilter vs. an OEM filter and there was no change in the power output in the back to back runs. This makes sense considering the intake is not the restrictive part of the stock system. The exhaust is. Once you go to headers/SSI/Pre-1974 heat exchangers then you may have freed up enough exhaust restriction to make a difference at the air intake side.

BTW, with CIS cars, clean fuel and air are the key to making these cars run well for the long term. K&N or any other of similar maketing hype filter will introduce more dirt into the engine.