Currently have a factory 914-6 air cleaner on the 3.0 in my 74 conversion. Question for the group is which system breathes better, the factory system or the K&N filters? I like the look of the two filters with the watershields but if the factoy system is better performance wise I guess I should stick with it? Please advise.

There have been tons of tests done and the K&N does not make much difference except being much louder. Personally I loved the sound of Webers with K&N air cleaners and a bursch quiet muffler. The intake sounds like a leman's race car. I used to drive back and forth in the Alameda tunnel just to listen to it. My current 3.2 with DME is quite boring in comparison.

I take it you are running Webers with rain shields, etc. I like them over the K&N filters. You nailed it; the looks and the sounds. K&N are good but I prefer the original look and sound. Some people prefer one over the other but I think they are each about equal and have certain advantages/disadvantages.

I am running Motronic injection on my 1987 3.2 Carrera engine and it has a K&N filter system on it. The original setup is about the same as K&N in terms of performance, protection, etc. I just like the K&N looks and have more room around the engine. This reasoning is not the case on your car if you are running Webers with Rain Hats.

These are my views, take the car and enjoy it to its maximum level.

Steve

The original air cleaner is really large and uses a single round air filter. You are correct it is very quiet and you cannot see the engine because of the air cleaner? I had the K&N's with watershields on my last 914-6 and I like the looks and the sound. If it is a wash performance wise I will change to the K&N's. Thanks.

An insider trick that most of you will gain 15 or more horsepower .....

I had the original non k&n filter with water shields and when I dyno my 914-6 stock 2.0 liter engine, I was getting aroun 95 to 100 ponies to the wheels

Then I removed the filters, dyno the car and was able to get 125 ponies at wheels

Knowing that, i bought off the shelf k&n filters to match same dimensions to original filters and was getting about 100 ponies

BUT

I was lucky yo know the owner of k&n and he asked me to bring my car to their shop and engineers

Well- the guys did some prototypes of various heights of filters to fit within the engine bay-- and they finally got the full 125 ponies at the wheels using their k&n filters-

Basically zero restriction-as if I was running without the filters

Lesson to learn:
So, you may want to check that you are not choking your Venturi stacks!
Original filters may be doing so to many of your 914-6s

It's not necessarily either/or. A little while back I found paper elements that fit
the K&N enclosures, except they are 1/4" taller and you may need to account
for that with the hold-down studs.

Write up here Look about half way down the page

This is how it would look without the watershields.
Click to view attachment

Everyone with their 3.2 sound ought to drive my 906 spec twin plug six at 8000 rpm with straight pipes. Big difference in sound compaired to a stroker crank at 6000


The stock filters better and suppresses sound.
Others don't filter and provide minimal air flow improvements at the expense of contaminating the motor

ITG offers the best performance from a hp perspective

I run both currently.. Over summer, and when school is not in session, I run the K&N filters. They look "better" and sound spectacular, but they are LOUD for the type of commuting I do once school starts back up.

So... I will go back to the stock 6 air box when I begin driving 90 minutes twice a weekend to and from school.

And for what it's worth, I haven't really seen any differences in power via the butt dyno with my 2.7 between the two setups..

Having measured the actual filter area on a number of K&N elements and compared them to the filter area of the stock paper elements, I can honestly tell you there is an ENORMOUS difference in the filter area, measured in square inches. Here are a few pix. (Both filters shown fit the same application.):

Click to view attachment

Click to view attachment

Click to view attachment

Note the obvious differences here. Were you to remove the border material and flatten out the pleats, you might be REALLY surprised just how big the difference is. (In some applications, there may be as much as 5-10 times more filter area in the stock paper filter element!) If there is less media, and the unit flows more air, it is obvious the air passages (pores in the material) must be much larger. That being the case, K&N (and others) have to use oil on the filter media. The air passing through the larger holes deposits SOME of the contaminants on the oil surrounding the holes. However, a significantly larger amount of contaminants are allowed to enter the intake airstream and go into the engine, vs. the OE paper filter element. The quantity of oil applied to the filter element is fairly critical, especially on cars which use electronic mass airflow sensors. The oil destroys the MAF in pretty short order. That expensive air filter seems like chump change when you have to buy a new MAF as well as a stock air filter, and have the car scanned and the CEL reset.

A few years ago I read an article written by an engineer with a mining company in one of the northern mining states. His company invested in K&Ns for their giant off road dump trucks. His conclusion was that the cost of complete overhauls made necessary by their use dwarfed any possible savings and convenience they could have EVER realized from the use of those filters. Save a few hundred bucks per truck per year, and spend tens of thousands, again per truck, on engine work, per year.

It's your car, and my opinion, albeit somewhat substantiated. Your choice.

The Cap'n

K+N is also washable + re-useable, which is also cost effective in the long run. I have found that good high quality U.S. Made cotton gauze filters work better than paper filters. K+N is probably the leader, but check out S+B filters, (the truth about air filters) .They specifically use a high grade cotton, and pleat their filters different from the leading brand. Over oiling is a problem with any reuseable air filter , S+B filters are factory oiled by programmed robots.
One of my engine builder customers uses our 3.2 high flow filter kits, for their POC customers /orange group, no complaints.
Marty

Can you please provide the mfg and number to this air filter?...Dah..found it via your link.
Thanks

Britain Smith did a test with a stock-ish airbox (with a cool velocity stack instead of the sorkle) and K&Ns and he found the stock airbox gave a smidge more torque and the K&Ns a smidge more hp.

edit: It was with ITG foam filters...please disregard. For what it's worth, the airbox made 10 lb/ft more torque.

"Cost effective in the long run"? For a stock 914 1.8 or 2.0, the K&N retails for 50 bucks +. The stock element is 12-13 bucks (OE Mfr.) For 4 times the money, plus the cost of a bottle of the special oil, you get less than a quarter of the filter area, you have to wash (an involved and time consuming process) and re-oil the filter, and you get a substantially higher quantity of contaminants flowing into your engine. Not yet mentioned is the physical deterioration of the element by heat. Most high mileage (i.e., used for 4-5 years of daily driving) K&Ns look like they've been in there for decades. I can't think of a system of calculation that could be used to determine that this scenario is more cost effective.

Let's go over this once more. Substantially higher cost. Significantly fewer square inches of filter media. The need to clean and re-oil the element at frequent intervals. Heat/time based deterioration. Passes far more, and far larger, particles of contaminants. Unverifiable HP increases (even if their HP claims were true, they may be over a small RPM range and are certainly not able to be felt "seat of the pants" by 99.9% of the drivers out there, except for verification by wishful thinking, a common improvement rating system). Beyond all those "features, you're paying for their advertising and car sponsorship, a BIG part of the selling price of the filters, and they NEED to spend YOUR money to keep sales numbers up for an inferior product. They might as well be selling those things on late night cable TV.

As with FRAM oil filters, it's clamor over substance.

This is FUN! Can we do it some more? Wanna discuss SS Braided Teflon brake lines or slathered-on orange RTV? How 'bout AGM batteries?

The Cap'n

I'll skip the argument of the k&n problems since I have no data.

But for me personally I don't want to worry about when to oil, how to do
it properly, and how to know if it was done properly.

david63...
let me know if you want to go to the K&N with water shields...I have a set and would like to get a stock system....thanks

the K&N sticker also adds weight to your car.....

Isn't there a discussion of this subject in the Bruce Anderson (RIP) 911 manual ?
Didn't they determine on a dyno that the stock air filter housing actually did quite well ? or didn't make less power ?

I have no words. El Capitano has spoken.

On my type one 2007cc Gene Berg engine that I built from a full kit in 1991 I saw no notable wear on the top end at it's 60k mile head check several years ago.
K&N on DCNF 42 webers.
This winter I'm going to do a major overhaul on it because it's past time for it, so I'll be checking everything.

All the engines I've built and few I've checked running K&N's I have never seen any unusual top end wear. Unless you count DAPO's that have dropped nuts and washers down their carbs.

I wouldn't and never have run K&N's on stock engines, just wasn't worth it.

when the k&n filters are no longer reddish pink it's time to go thru the cleaning hassle. soak to clean, AIR dry, oiling (but not too much. just right). i've seen plenty of k&Ns that were BLACK. "you need to clean and oil your filters", "why? they're k&Ns". when you have to run out and buy a NEW bottle of oil after doing 1 filter that's a hassle. for about the same price as the bottle you can purchase a new set of paper filters without the tops and bases.

Actually, the K&N's filter better when dirty. All that crud in there makes the pore size smaller. You are supposed to run them until they start loosing flow. You can use a vacuum gauge to check flow resistance.

Needless, I will not run one without and Outerwears over it. They just pass too much dirt. I come from a off road backround, and I have seen motors "sanded" by a K&N.

Also, the ones on my ATV's tend to shrink at the rubber bases. According to K&N, they do not like the smog in the air.