914und993

I'll bet a properly maintained K&N does a pretty good job, and could possibly buy a few more horsepower in a 964, but with a big caveat:

1. As the oil in a K&N picks up more dirt, it becomes less efficient at filtering out the dust. This is in contrast to a paper filter that actually becomes MORE efficient at filtering particles as it fills with dirt, albeit with an increase in air flow restriction.

These types of filters are popular with racers, but under that kind of severe duty the engine is likely to need a rebuild for other reasons before inhaled grit induced wear becomes an issue.

If you want to run a K&N in your street car, you also need to be prepared to be meticulous about its maintenance - cleaning it often enough that it is still an efficient dirt filter.

If you really want to be compulsive about it, use the K&N for a fixed mileage (say your normal oil change interval). Then get an oil analysis. Now run with a paper filter for the same period. Get another oil analysis. Compare levels of silicon (dust) and wear metals between the two. If you don't see them higher with the K&N, then you must be doing something right and you have some data to back it up.

Chip

pzull

Here's an independant "lab-ish" test:
http://www.mkiv.com/techarticles/fil...t/2/index.html

Apexi has added advantage of much better air-flow due to smoothing

914und993

The HP results of that test above bear absolutely no relation to a 964.

Any gains of alternate airbox/filter systems would be entirely dependent on how restrictive the orginal system was. The fact that the many different designs of free flow air filter all achieved roughly 13 hp increase in the Supra bespeaks an exceedingly poor original factory design.

The 'dirt' tests were certainly eye opening!

Chip

pzull

Actually I was referring to the dirt tests....since point on hp gains is too contoversial....I cant make up my mind if it has any difference or not although i think cold air induction does make a difference

Adrian

If anyone wants to read in some detail about air induction, how it works, what and where the restrictions in a design are, I recommend picking up a book written by Charles Probst, SAE. Charles had sadly passed away but his book Bosch Fuel Injection and Engine Management by Bentley Publishers is still available.
Charles Probst was and remains (via his published works) regarded as a genuine world expert on fuel injection systems.
When the subject is researched properly, it will be discovered that simplistic views of more airflow or free airflow is better, are inaccurate.
An air induction system is a tuned system just like the exhaust and if improvement are sought a number of modifications are required.
However the problem of what to do with all this extra air must also be addressed.
Power is created by igniting a fuel/air mixture. What is aimed for is the most explosive or powerful mix for any given set of conditions. Changing one does not necessarily improve this mix.
For the record the biggest restrictor in the 964 system is the ability of the air flow sensor to actually measure the amount of air going into the engine. The other physical restrictor is not the air filter but the throttle valve size which is matched to the air flow vane sensors' measuring abilities. Remember that the normal 964 engine was designed to meet emissions targets whilst providing the best power output. Changing this is not easy and there are no demon tweaks just very expensive ones.
Ciao,
Adrian
964C4

Arjan B.

My Green air filete service set says: "Use the Green filter oil in a lean way, too much oil will stock your air flow"

Christer

Yes, you have to do the job properly. Just fitting a larger throttlebody/air filter/exhaust system whatever does not necessarily mean any good gains. If you create synergy all the way through the engine then there is good potential of hp/torque gains. Of course, this is very expensive.

With any luck I shall be in a position to tell you more about what works in a couple of months. I have started Stage 2 of the upgrade project very recently and will share more information as I go.

Douglas_T

I have used them for years as well with no problems...Some people do tend to rush the process with over oiling perhaps?
I think its a good product that gives results...

Adrian

Dear Douglas,
I actually agree with you. K&N filters are excellent and give excellent to superb results on many autos. The 964 is just one that it does not. The comments by myself on this forum are ONLY directed at the 964.
Ciao,
Adrian
964C4

Christer

Adrian

I was wondering if I could join Nice Guys Anonymous? Despite the fact that I am rude, clueless and never shut up I feel I could contribute to this organisation. Are you in need of for example a Sales Director? Hopefully we can spread the word about this last bastion of straight-speaking-whilst-making-friends-and-not-upsetting-anyone.

Adrian

Dear Christer,
You are more than welcome to join. I still have many senior positions to fill, Sales director is one of them.
Ciao,
Adrian
964C4

Christer

It was a tough interview. Another set of business cards to get printed....

ian c - u.k

can i be minister in charge of propoganda ???
or perhaps the escape commitee ??

Christer

How about Global Head of Punctuation?

Roygarth