For all you K&N devotees, A little comparison ............. Options

[Cap'n Krusty]

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!

[ericread]

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