Here are some comparison photos and a little math for your viewing pleasure. I might mention that you can SEE THROUGH the K&N, down in the folds.

This particular part fits a 2003 MB C320 Kompressor coupe. The K&N has 128 square inches of filter media, the Mann has 1752 square inches! That's over THIRTEEN TIMES the filtering area!

So?



But really, thanks for the comparison. Makes is pretty obvious.

That less of a restriction has to come from somewhere, it comes from filtering

Most of my friends with turbo cars literally just put wire mesh over the inlet. Then again they swap turbos ever season.

Just eyeballing the things doesn't prove how well they work or don't work. Do you have some way of measuring the amount of particulate each one catches in a controlled environment?

Here is another filter test. I use the Apexi which filters best. The K&N are average and not worth the hype.

Filter Test

Do you use an Apexi in your 914? If so which one??

I just use a cone filter with an intake from Home Depot Racing.

Trekkor??? Is that you?

There are plenty of studies out there. To pass the same amount of air through a smaller area, the restriction has to be reduced. Fewer square inches of media, larger passages through that media. To increase the amount of air passing through, you have to increase those holes to an even larger size. In this case, you can SEE through the filter media. That means relatively BIG stuff can get past it.

The Cap'n

I used to wipe fine sand like stuff out of my intake pipe on my K&N 'filtered' GTI. Every car that I have worked on that had a K&N had dirt on the throttle body. My old Mustang had one and has pretty serious cylinder wall wear at 25,000 miles (I had it apart when I wiped a few the rod bearings when the oil pump drive snapped.)
Steve

I run a K&N, a Tornado, and fuel line magnets to maximize my engine.

For those of us using dual carbs, what aside from K&N is there to use as an air filter? Is there even a paper element option for us?

Zach

Yes, but you won't like it...
/6's used a paper filter with dual carbs 40 years ago; 356's and 912's long before that. The filters are readily available but you'd have to do some fabrication for the housing.

Just make sure your K&N is well oiled. One of the big causes for crud getting past is because of not maintaining them properly.

Unfortunatly they are about the best we have for our carbs but if you use rain hats and oil them and clean them often they will work well.

Outerwears help a lot too. I have run a K&N on my desert toys since I got them. Always with an Outerwear on them, and I have never seen anything get past the filter. My buddies that don't run them get grit in their engines often.

I know that the K&N's don't filter that well, so I use the prefilter. It's a lot easier to clean than the K&N too.

The K&N filters don't even increase the HP. A recent article in Grassroots MS has an article where they dyno test an engine and try different changes. When they put on the K&N filter they got miniscule improvement...pretty much noise level on the dyno. Anyway, they proclaimed a HP increase. I lost a lot of respect for them, but I guess they gotta keep the advertisers happy.

Great thread!!! ...... I have done flow tests of my own using paper vs K&N ....... the K&N produced zero RWHP gains over paper in my test vehicle ....... even though on the flow bench they outflowed paper by a mile ....... anyway all my tests show is the factory sized the paper elements adequately to where K&Ns did not make a difference for the better.

I read that Grassroots article, it was a BMW 335 i think. It always seems like certain mods that make power on one car don't make power on another, especially ones with new-fangled computers. I'm going to keep buying K&N's just because they are made in so many sized that I can get one to fit anything I need it to.

Ohh, and Mark... I found a tornado at the Pink-N-Pull once stuck inside the intake pipe I needed for my truck. I couldn't get it out without destroying the rubber pipe. I was pissed. The truck it came out of had the entire interior spray painted yellow and white and blue........seats, carpet, dash....everything.

You also hang out here.

I agree with Krusty,

Read the article that K&N puts out, it's on their site. It says that their filter's are only 80% effient, and are for racing applications only, like engines that will be torn down often!!

I would rather use something that does what I'am paying for it to do, like actually filter 100% of the crap out before it sand blasts the insides of my engine.

It's good, when you have to replace your filter, it's doing it's job.

People who use K&N filters for the street are turning their engines into expensive Vacuum cleaners.

Anyone with a K&N filter want to drive up and down my street? Because the street cleaners are on stike and it's starting to look like a beach out there. Sandy!

Just my 2cents

westgl

you kill me!

I do agree that the K&N filter will not perform to specifications unless you clean and oil the filter per the K&N instructions. But it should be noted that a properly oiled filter should not be directly compared with a dry filter, as the filtering mechanism and flow characteristics between these two filtering media are not similar.

I would have a hard time accepting specs on HP increases with an oiled filter, but I feel my 2.0 L engine has a bit less air restriction using a K&N versus the stock airbox. I can quickly substitute the stock airbox for the stock unit, and I do feel less acceleration with the stock airbox. Then again, it may not be the filter media itself that makes the difference, but just be the flow restrictions of the stock airbox itself that could cause the difference.

Although Krusty will claim a conspiracy theory regarding any information from a vendor's website, here is a short excerpt from K&N:

Air filters are not measured by micron size. As an industry standard, air filters are tested in accordance with the ISO 5011 test protocol to measure capacity (the physical amount of dust a filter can hold before cleaning is necessary) and efficiency (the filter's ability to trap and hold dust). See technical service bulletin 89-5R from the Filter Manufacturer's Council. The dust selected for the test contains a specified distribution of different particle sizes according to ISO standards.

The content of the two most commonly used types of ISO test dust for air filters is as follows:

ISO COARSE TEST DUST
Particle Size in Micrometers (Microns) Percent by Volume
(+/- 3%)

001 - 005---10.5%

005 - 010---11.5%

010 - 020---14.0%

020 - 040---25.0%

040 - 120---37.0%

120 - 180---02.0%

As has become customary in the automotive industry, we use Coarse Test Dust for gasoline engine air filters and Fine Test Dust for diesel engine air filters. This practice of using different grades of test dust developed because Diesel engines require higher levels of filtration because they operate at much higher compression and require tighter tolerances than Gasoline engines.

Our testing has demonstrated that on average, K&N replacement air filters and air intake systems have a cumulative or Full Life filtration efficiency of between 96 and 99%. Different filters test at different efficiencies due to changes in their shape, surface area and relationship to the direction of air flow through the factory air box or test housing. Like most air filters available in the USA, our filters will provide all the engine protection you need.

For more information on our testing, see our K&N Product Testing page.

There is no published requirement for vehicle filtration. Car and truck owner's manuals are silent on the issue and you will find very few companies that even credibly discuss filtration efficiency. We believe this demonstrates that most air filters sold today provide adequate levels of filtration. Particularly when compared with the filtration provided by fuel and oil filters.

The fact is that an engine is not a pristine environment. Fuel enters after passing through a fuel filter, combines with air which is ignited to explode in a pressurized chamber. The combustion is not 100% efficient and leaves residues behind that must be flushed from the engine. Engines have tolerances or measured gaps between surface areas. While there are few if any studies on engine wear, it would seem reasonable to speculate that particles less than 5.5 microns create little engine wear unless ingested at very high levels of concentration. As support for this theory, consider the filtration levels provided by fuel filters and oil filters that sometimes tout their ability to filter particles above 10 or 20 microns.

Should I install the largest filter that will fit in my race vehicle?

If an existing K&N filter is large enough to provide negligible restriction, a larger than required filter will not affect the amount of air an engine can take in, however, it will lengthen the filter's service interval. A longer service interval can be an important factor when racing in dusty, dirty environments.

Eric

Not that applies to our engines, but I repeat that K&Ns, when properly oiled, are noted for contaminating and rendering useless hot wire and hot film MAFs. Save on filter changes, blow 10-20 times the savings on EACH MAF replacement.

The Cap'n

If there is anyone out there with a paper filter setup for IDF's, could you post pictures to give us some ideas?????

Thanks,
Harvey

All you have to do is find the correct size (diameter and height) round paper filter. It will easily bend to fit the oval filter housing of the IDF.

I searched the web a little and couldn't find the article, but there was a mining company that used a lot of air filters on thier heavy equipment, so some of the engineering guys (who are also car guys) wanted to try K & N's to see if they saved money and protected the engines better.

The article stated the K & N's were much worse on the engines than a high quality paper filter.

Too bad I couldn't find the article.

Exactly what it did to my ML320. 7 years ago. Yanked all my K&N's and put them on eBay.

I have that bookmarked somewhere and will post it when I find it. The author was very biased toward the K&N and probably would have got a big fat bonus if he could show that a K&N type filter would work and save the company money (lots of money in this case.) The tests were a total bust that showed the K&N filters did not actually filter and let lots of dirt into the engines - not real good in a mining environment.
Steve

My 964 had a k&N when I got it, so I went on the Rennlist 964 forum looking for others' experiences. Turned out it was a major hot topic over there: lots of evidence to suggest the K&N sucked ('scuse the pun), although many who had forked out for them were outraged at the suggestion ...

So I replaced mine with the stock air filter, just to be on the safe side. The main value of those cars is in the engine, and there was no way I was going to risk knackering it by believing a load of advertising hype.

I didn't notice any performance difference whatsoever afterwards. My 2c.

By any chance does anyone know of a standard paper filter that will fit 911 Weber carb filter housings ?

911 used the same filter from 1965 through 1973.
Mahle-Knecht element.

911 Air Filter at Pelican