K&N - is there any point?

Hi All,
I'm servicing my 3.2 Carrera and wondered if there was anything to be gained by swapping the standard filter for a K&N. Would this make any difference to the power output, noise levels or driveability? The engine is completely stock, although I will be replacing the mufflers with Hayward and Scott stainless straight through-pre muffler and one in/dual out rear mufflers shortly.
Any help or experience would be very appreciated.
Thanks in advance.

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86 911 Supersport

Yes, research has shown that K&N will improve air flow to the engine.

Adam Roseneck


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1978 911SC 3.0
roseneck@cyberbeach.net

Debatable!.
I have one fitted. It makes engine work easier (more space). ButIt does not enble more air get to the engine.
Check past threads on this using the 'search' tool. The stock air box has the advantage of taking cooler ducted air than the K&N which takes it from 360 degree area.
It does no harm and looks cool
But with hindsight, would I have fitted it now after reading all the controversey, NO!.
Ask Kurt B who is now converting his car back to stock so he is not a 'gross polluter'.
rgds Ben

More hissing noise, annoying.

It depends what you are talking about. K&N makes 2 versions. One is a high flow version of the stock shaped filter. The other is the "filtercharger" which bolts to the intake once you remove the air box. I have the stock filter. It claims to increase flow by 80%. It seems to make a small difference.

Nick.

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Nick Shumaker
1982 911SC Coupe
nickshu@yahoo.com
PCA -- Rocky Mtn. Region

Nick, I was referring to the stock replacement, not the cone type.

Have to respectfully disagree with Orb. I have a cone filter as part of my MAF system. The sound in the cabin above 4K rpm is awesome. I have a good friend with a 996. . .his biggest frustration is that my car sounds so much better under hard acceleration.

I have the K&N cone replacement over the stock airbox and it definitely changes the intake "sound." It might also allow a more streamlined flow into the throttle body over the stock airbox to give better air flow at various rpm's which may equate to a few hp here and there. I think the problem is when the factory does something to disturb the airflow in favor of noise reduction. If you can remove that artificially created turbulence you can probably enhance throttle response and power - of course at the expense of silence.

On just a replacement filter in the stock box... Even if the air filter provides roughly 80% more airflow than a paper filter, that is probably when put on a test that truly tests the upper limit of airflow on the filter. Does that really apply to the filter once on the car? I doubt in many cases that the air intake bottleneck will be the filter element, but will be the airbox, throttle body, exhaust, or some other combination of things.

...but then again, I just might be simplifying things.

Brian Smith
'91 C2

The answer is a resounding NO!
A K&N filter will not increase flow on almost all cars, including the SC and Carrera.
Bruce Anderson's dyno tests have conclusively shown no gain with the K&N over the stock filter. In fact, the tests have shown the engine will not produce any more power if you run no filter at all.
Why? Because the filter is not the bottleneck. The stock filter can flow more air than the engine can use. Therefore, increasing filter flow is meaningless.
These cars are well designed.
K&N is junk science. They claim "our filters flow 80% better than stock" but fail to mention that the stock filter flows more air than the car can use in 95% of applications.
A good example is in this months Euro Car. They discuss the Brabus Mercedes C 3.8. Brabus (a very well respected MB tuner) takes a stock 3.2 217 hp engine of the new C class and bores it out to 3.8 and over 300 hp. And, guess what. They use the STOCK air box and air filter. Because it not only flows enough for the stock engine it flows enough even for a bored out monster motor.
So, NO MATTER WHAT YOU DO TO THE INTAKE SYSTEM UPSTREAM OF THE THROTTLE BODY you will not increase power on just about any Porsche 911, at least since the SC cars. (there is at least one exception that anderson has found, though, one of the 964 cars can benefit from a modified airbox. But, that is the rare exception, not the rule).
K&N, Cone filters, etc. on a 911 are useless, other than serving to help wear the engine out faster.

I have the K&N stock replacement type filter and I believe my engine runs at least 10-20 degrees cooler than with the stock filter.

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Dan S.
1974 911 Targa

I'm probably wrong, but the only benefit I have heard is that with K&N filter they are resuable, just wash & rinse. No need to really replace them.

I agree with Jim T. I do not think that they filter as well no matter what they claim. I've seen 4 examples (including my own) in Porsches where when removed, there is dirt in behind the filter. When I switched back to a Mahle filter, the dirt went away. I've talked with several racers who run 951's and 930's, and they will not use a K&N because of stories of chipped vanes in the turbo when running K&N's.

I hear Amsoil makes a good filter.

If you read their ads closely, they will claim a lot of things (mostly unmeasurable things, or irrelevant things, like how much more they can *theoretically* flow), but they won't claim they filter better than stock paper filters.
Its because they don't and they don't want to get busted for false advertising.
So, basically, on a Porsche, using a K&N gets you decreased filtering in exchange for no performance gain. Not a good trade-off.
(Sure, they are reusable, but how much money are you going to spend on factory OE paper air filters during the life of your car??)
Again, another one of those "mods" that people do without really *knowing* why they tossing a factory part, on the *presumption* that the factory part is somehow inferior. All based on self-serving and misleading advertising.

'Junk Science' is an equally applicable term when you use anecdotal evidence to say the K&N *increases* engine wear.
Honestly guys, if they were that bad, nobody would go near them!
I think they fit into the category of a cheap owner fitted mod. Because of this, every man and his dog has an opinion on how good they are/how useless they are: it's easy to comment.
I use one and have zero complaints. I've always used them, even before I started thinking Bruce Anderson has the last word on engine mods. Anyone here read David Vizzard?

The 'K&N' filters are many and varied. The only thing they all have in common is the filter material, and this has been proven to filter and flow effectively on countless occasions and tests. Serves you right if you try to slap some wierd looking pod on your motor and claim the K&N is useless. It's not exactly rocket science.

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'72 911 TE