Air filter facts – 2 things you should know.

Posted on 07. Aug, 2008 by in Filtration & Induction, The Store

Simon looks to the skyGetting air into your engine is like getting oxygen into your body. Using a dirty filter is like sucking on a cigarette. Low quality air and not enough of it.

It amazed me to find out the difference that cleaning my induction kit gave me. Not only did the engine feel snappier, but it also got me a few more MPG to boot. I spoke to Robin Evans, the Sales Manager of K&N for the answers to a couple of questions about filter performance.

1. How much does a dirty filter degrade airflow.

As a filter becomes more and more clogged, the pressure inside the filter drops while the atmospheric air pressure outside the filter remains the same. It’s like using your lungs to draw the air out of a plastic bottle. When the pressure differential becomes too great, the bottle will collapse.

The same thing could happen to your filter if its not cleaned. An excessively high pressure differential created by a restricted filter can literally pull dirt particles through the filter material.

In other words, the performance of a filter, to actually filter dirt, is severely compromised, as the pressure differential sucks through dirt.  Air flow through the filter is also reduced substantially and has a very adverse effect on power as it loses in excess of 5% of its flow capacity.

2. Can oiled filters damage a MAS sensor in my car?

Theres been talk on many forums about oiled filters drawing the oil through the filter and damaging the MAS sensor further down the line.  K&N has conducted a lot of research into this potential issue consulting  garages in the UK and US and examining hundreds of damaged MAS sensors.

The overriding evidence from these investigations has shown that in each MAS sensor tested that the incorrect grade of filter oil had been used. The oil used in genuine K&N re-oiler kits has been developed to be at the right thickness for its application. If a lighter/thinner oil is used the pressure differential accross a filter could be enough to pull through the oil.

So, looking at that, its about time I got myself a K&N cleaning kit

30 Responses to “Air filter facts – 2 things you should know.”

  1. T-UNIT

    07. Aug, 2008

    i think K&N are cak…theres better n cheaper on the market…

    my 2 cents…

  2. aj

    07. Aug, 2008

    i beleave that a lot of people are full of sh*t to be honest k n n are great and that final

    stop being skool boys there are many filters on the market

    ift comes down to this if you dont like them dont buy it simple people :)

  3. Dave

    07. Aug, 2008

    Skool is spelt school. Oiled filters DO damage MAF sensors. Fact. K&N have to deny this as all their filters are oiled. Foam or metal mesh all the way for me.

  4. Nick Morton

    08. Aug, 2008

    A Million Mile warranty and the most established brand on the market means they have lots to lose if they don’t get the product right. At the end of the day they allow your car to breath and give better mph and drivability. When it comes to a service too you don’t have to have a new one, just clean it.

  5. Simon Morton

    08. Aug, 2008

    Foam filters are oiled though? Metal mesh will flow a lot of air, but by its nature its not going to provide the filtration level of other materials.

  6. Dave

    08. Aug, 2008

    I have 3 mates with K&N filters on Golfs and all of them needed new MAF sensors. I’ve run both a Blitz and Powertec and my MAF is fine. Oil does damage MAF sensors, we all know it.

  7. Robin Evans

    08. Aug, 2008

    It is our policy at K&N not to release a product unless it makes demonstrable differences to the application it is designed for, we also fully dyno test all of our products and as stated earlier guarentee them for 1 million miles.

    I can’t speak for all oiled filters but the fact is that no K&N product has or will ever cause any damage to a vehicle or its’ component systems. I have included this link for further information

    http://www.knfilters.com/MAF/massair.htm

  8. Dave

    08. Aug, 2008

    Just propaganda that. There’s more than enough anecdotal evidence to say that K&N do damage MAF sensors. You’d hardly want to admit it would you as the claims would come thick and fast!

  9. Robin Evans

    08. Aug, 2008

    Some information I found on Honest John’s website

    “I know the Bosch MAF’s are notorouisly unreliable on VAG cars – I had one replaced at a main dealer 50K ago for £200 for the sensor and £65 labour – now that’s what I call an hourly rate given I think I could do the job in 10mins if I had the right removal tool. I was thinking of holding a spare for the inevitable failure – no doubt at 2am one Sunday morning whilst on some sort of life or death mercy dash”

    Before coming to K&N I workrd for a company with over 200 company cars and also had MAF failures with dealer serviced VAG group vehicles (as well as other marques too).

  10. Liam

    09. Aug, 2008

    I’m knew to all this car tuning and air filters. Could someone tell me what an MAF sensor is please? I have a Golf with an K&N 57i filter fitted but what is the better make out of K&N and Simota?

  11. kirsty

    10. Aug, 2008

    my k&n on my punto is great. only down fall with the different filters is the petrol. other than that ther fine. recomended by my uncle n bf who r both mechanics

  12. Simon Morton

    11. Aug, 2008

    MAF Sensor, or Mass Air Flow Sensor, detects how much oxygen is coming through the filter into the air intake, so that the engine can calculate the right amount of Fuel to go with it. K&N is much better than Simota.

    More info here

    http://en.wikipedia.org/wiki/Mass_flow_sensor

  13. mikel

    12. Aug, 2008

    I’ve just purchased K&N typhoon system and gonna test it soon. Well, i didn’t have any problems with my previous car with K&N 57 filter so i hope this one will be fine too.

  14. Kev

    18. Sep, 2008

    I used to work for a Volkswagen/Audi dealership and I’ll let you into a secret concerning the MAF’s on all VAG cars. The MAF sensors fail regularly on these cars because of the following reason:

    The engine management system on the car puts the MAS through a ‘burn off cycle’ every X thousand miles (based on mileage and the type of mileage driven), this is to clean any unwanted particles of carbon etc off the mesh inside the MAS which affect its efficiency. A current is sent through the MAS heating it up to a very high temperature in order to do this. It usually performs the ‘burn off’ just after the car’s engine is switched off.

    Now, here’s where the problem occurs. As the MAS is cooling after the burn off, if the car door is slammed shut, the shock can shatter the elements inside the MAS causing it to malfunction. This is why so many fail.

    Its nothing to do with your air filter, as this happens all the time on cars with standard air filters. So now you know. :)

  15. Simon Morton

    19. Sep, 2008

    Great answer. Sneaky VW….

  16. Colin

    03. Oct, 2008

    Save money get a Max power cheapy from asda have been recomended by mechanics and friends to be best for my engine then K&Ns

  17. Mojo Jojo

    02. Jan, 2009

    After running a K&N for 3-4 months my engine started acting up cutting out at speed or idle pretty much whenever it wanted to. I spoke to my mechanic and he swiftly installed a pippercross and a new mass air flow sensor. 9 months later and no problems.

  18. will

    27. Mar, 2009

    I had the exact same problem with a K&N induction kit on my golf. Ive now put my air box back on and swapped to a dry Pipercross panel filter, after talking the car to tuning company for a remap. It now runs great.

  19. weeboy

    16. Apr, 2009

    i had a k and n filter on my polo gt, great noise and good power gains, i then sold it and put my standard airbox on it, it felt slow and crap, k and n are good

  20. dave

    24. Apr, 2009

    sod k&N i ve just fitted a supercharger

  21. UK Dave

    12. May, 2009

    Gotta be honest i’ve ran probably 6 K+N filters on various cars without problem-However it depends generally on the type of sensor.
    Ive got a 2000 uk impreza turbo and deliberately avoided K&N as the 99/2000 impreza`s are tempremental to oil vapour across the wire element of the maf sensor.

    First choice were Green. I ran that without a problem till the cleaning no longer made it any cleaner(4-5yrs)Then replaced with a jetex cone filter-both of these i feel are a lot lighter oiled than a K&N,generally the k&N`s ive bought have had the red oil coming off on the bag they`ve been sealed up in. I never had this with green or jetex-wouldnt risk a K&N on mine however if were forced into it would maybe try a CAI kit like the typhoon as at least the filters further away from the sensor.Theres definately alot of impreza owners reluctant to use K&N but willing to use other simular filters as other ppl above have mentioned with their cars.

  22. simon

    12. May, 2009

    well i run a drift spec 1.7 340volvo running a k&n bolt on,
    it works a dream(no maff for me)and i also know about the burn cycle on the vag mafs as i had i 1.8 turbo beetle and know they have chocolate mafs (like a lot of cars)classic wrx too!!!!!!

  23. Aron Hawes

    12. May, 2009

    from http://www.knfilters.com re dirty filters

    “4. How often do I need to clean my K&N air filter?

    If you have not experienced a decrease in mileage or engine performance, chances are your filter is fine and does not yet need cleaning. To be more specific, the filter does not require cleaning if you can still see the wire screen on the entire air filter regardless of how dirty it may appear. When the screen is no longer visible some place on the filter, it is time to clean it. When used in normal paved road, street or highway conditions, our replacement air filters that fit in the factory air box should require cleaning every 50,000 miles and our large conical filters on an intake system should require cleaning every 100,000 miles. When used in dusty or off-road environments, our filters will require cleaning more often. We recommend that you visually inspect your filter once every 25,000 miles to determine if the screen is still visible. ”

    so there for you dont need to clean the filter untill it is so badly caked in dust and general dirt that you cant see the wire casing around the cotton filter. POTN find another product to force on customers.

  24. PhilCavSRi130

    12. May, 2009

    I’ve used KnN filters on every car i’ve had (Vauxhalls) and never had a minutes bother. Seems the newer cars are too fragile and temperamental for such an easy modification. In my opinion new cars are over engineered and complicated so any change of filters exhausts etc throw problems up with software and sensors!

  25. Nick

    12. May, 2009

    Hi Aron

    Thanks for the post. We value your feedback. Regarding airflow, a clean airfilter is a good starting point, but using a hi-flowing filter like K&N or Pipercross will improve your engines performance on fuel consumption and overall driveability.

    If the filter is black, then get it cleaned. It only takes few minutes to check. I don’t quite understand your point on forcing product onto customers; We’re here to help people buy :)

  26. MIKEB

    12. May, 2009

    Its usually not the K&N that kills the MAF, but over oiling by the person.
    K&N aren’t the only filters which require oil, so saying K&N’s kill MAFs is a bit of a sweeping statement.
    I use a K&N 57i, which has been cleaned and oiled, 20,000 miles in, and still OK

  27. tanthony nichols

    15. May, 2009

    I have used K&N cone filters on my last two cars both fiesta`s(1.3 and 1.6i)over the last 5 years and have had no problems whatsoever,love the sound and have recommended it to friends

  28. Phil

    07. Jun, 2009

    love the banter!

    its obvious really, air filter make shit all difference to MPG and performance, but cleaning it regularly wil keep it lookin nice..

    clean it once a year may be hard ;)

  29. Nick

    08. Jun, 2009

    Hi Phil, Induction kits sound great, look great and DO improve performance, but then we would say that!

  30. matt

    22. Jun, 2009

    i have run almost all filters and would have to say that i prefer k and n and pipercross. The problem is with older cars k and n work brill, but with new cars i found it didnt so i then switched to piper!! which powergains and increased mpg was astonishing for a bolt on mod. It all depends on the age, car an type of uel and ecu system the car runs

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