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Performance air filters
- Thread starter AntStark
- Start date
Is an OEM filter better than a K&N type? In a word - yes! Perhaps I should explain the reasons for my dislike of these admittedly popular add-ons.
There is a lot of information on the internet regarding comparative testing of K&N and BMW E36 M3-sized air filters, the general result being that the BMW filter has over 5 times the area of the K&N, and a better flow rate when both are equally soiled.
When new and clean, the K&N has a slightly higher flow than the BMW filter, but due to the smaller area, this advantage falls away sharply as fouling builds up. Remember that a smaller filter with a similar flow rate means a lower level of filtration.
I would love to know the conditions where a K&N filter only needs cleaning after the 'Up to 50,000 miles’ which they claim - maybe in an operating theatre?
With regard to the fouling problem with hot-wire airflow sensors (which is hotly denied by K&N) Rob Levinson from UUC Motorwerks says that:
‘First, conclusive tests from independent labs show that K&N filters, no matter how well-oiled and cleaned, let through huge amounts of large particulate that damages engines. Oil analysis shows five times as much silicate contamination. Additionally, the oil from these filters tends to contaminate the MAF and cause an engine-damaging lean-run condition.’
Oiled gauze air filters such as K&N are widely used on large turbocharged marine and stationary engines (pumps and generators etc) which operate in good conditions and receive plenty of maintenance, but one never sees them fitted to construction machinery, or large trucks which work in a poor environment.
In such cases, the use of a cyclone filter (as on a Dyson vacuum cleaner) followed by an oil bath filter has been universal for over seventy years . . . but perhaps manufacturers such as Caterpiller and Scania have not discovered the benefits of fitting K&N filters!
There is a lot of information on the internet regarding comparative testing of K&N and BMW E36 M3-sized air filters, the general result being that the BMW filter has over 5 times the area of the K&N, and a better flow rate when both are equally soiled.
When new and clean, the K&N has a slightly higher flow than the BMW filter, but due to the smaller area, this advantage falls away sharply as fouling builds up. Remember that a smaller filter with a similar flow rate means a lower level of filtration.
I would love to know the conditions where a K&N filter only needs cleaning after the 'Up to 50,000 miles’ which they claim - maybe in an operating theatre?
With regard to the fouling problem with hot-wire airflow sensors (which is hotly denied by K&N) Rob Levinson from UUC Motorwerks says that:
‘First, conclusive tests from independent labs show that K&N filters, no matter how well-oiled and cleaned, let through huge amounts of large particulate that damages engines. Oil analysis shows five times as much silicate contamination. Additionally, the oil from these filters tends to contaminate the MAF and cause an engine-damaging lean-run condition.’
Oiled gauze air filters such as K&N are widely used on large turbocharged marine and stationary engines (pumps and generators etc) which operate in good conditions and receive plenty of maintenance, but one never sees them fitted to construction machinery, or large trucks which work in a poor environment.
In such cases, the use of a cyclone filter (as on a Dyson vacuum cleaner) followed by an oil bath filter has been universal for over seventy years . . . but perhaps manufacturers such as Caterpiller and Scania have not discovered the benefits of fitting K&N filters!
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