air filters

The Technology behind K&N High-Flow Air Filters

World leading manufacturer of performance air filters, K&N Engineering elaborates on the technology behind its high-flow air filters.

K&N Engineering is the world’s leading manufacturer of washable, performance air filters. The filters offer higher air flow and engine performance, owing to some unique production methods that have helped the brand establish itself as a market leader in performance air filter technology.

Filter Technology

K&N filters use a significantly different technology than other types of air filters.

Surface Loading

K&N filters use a significantly different technology than other types of air filters. Most disposable filters are barrier filters: their filtering media act as a physical barrier to dust particles. Air can’t flow through the media once the pores get clogged by dust particles. This principle is called ‘surface loading’.

Depth Loading

K&N air filters, on the other hand, are manufactured using 2, 4 or 6 layers of cotton fabric (as shown on right), the medium absorbs dirt and dust particles instead of physically blocking them, a process known as ‘depth loading’.

The pores in the material continue to let air flow through as the filter absorbs dirt in the medium.

3 Key Elements

K&N air filters are designed specifically with their applications in mind.

The three key elements behind the production of the filters are air flow, efficiency and capacity (filter life). The pleat height, pleat count and the weave count (density) of the cotton along with the number of layers used are all taken into account while designing the filters. All these variables work together in the final product.

The filters are then factory-treated with specially formulated filter oil, before being released to the market for sale.

Filtration Test Facility

All K&N filters undergo air flow and filtration efficiency testing in a state-of-the-art, in-house filtration test facility. The filters are designed to allow more air flow than their OE counterpart; their efficiency and capacity tested by feeding specific test dust to a test filter in a controlled environment. The ISO 5011 test protocol is used to ensure that all results are comparable and up to K&N’s quality standards.

Efficiency Rating

Once the test stand has automatically shut off at a specified filter restriction, the efficiency is calculated by processing the mass of dust fed and the condition of the air filter housing and the filter itself. Any dust that passes through the filter during the test is captured in a ‘high density’ absolute filter and this data is processed to draw a full life efficiency rating. Many K&N filters achieve 98-99% efficiency, owing to product design quality that offers a longer service life and much lower restriction than other brands. All of this sets K&N High-Flow Air FiltersTM apart and makes them a perfect choice for specialist filtration needs.


FPS stocks more than 300 parts from the range of High-Flow Air FiltersTM to cover all major vehicles.

Popular parts include:

  • 33-2865 for Audi A3 1.6 (2009>)
  • 33-2955 for Ford Fiesta 1.6 (2008>)
  • 33-2787 for Vauxhall Astra 1.6 (2004-2009)

For more details and further stockist information, please speak to your local FPS representative.


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