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K&N Air Filter

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    Posted: 09 Mar 2016 at 4:35pm

My car is going to breath better once this has been fitted..

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Mike Fishwick View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike Fishwick Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2016 at 6:38pm
Sorry to be pessimistic, but I doubt it - all it will do is to make more noise, which is the reeal reason people fit these filters! 

The first problem in persuading the engine to breathe more efficiently than with the standard set-up is that the replacement filters - as shown - which replace the standard BMW etc air box are often fitted in the same place under the bonnet. 

This means that the engine is inhaling warm air from the radiator, the higher intake temperature reducing  volumetric efficiency and also increasing the likleyhood of detonation.  Engine efficiency therefore falls, regardless of any increased airflow.

There is a lot of information on the internet regarding comparative testing of K&N and BMW E36 M3-sized air filters, the main point being that when clean, the K&N filter has a slightly higher flow rate, which means it has a lower level of filtration. Even if you remove, clean, and re-oil your K&N very regularly, it will not protect your engine as well as the BMW original.

Due to its smaller area, however, this small advantage falls away sharply as fouling builds up.  As the BMW filter has over 5 times the area of the K&N, it  therefore has a far better flow rate when both are equally soiled.

I would love to know the operating 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 5x as much silicate contamination. Additionally, the oil from these filters tends to muck up 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 also used 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!



Edited by Mike Fishwick - 09 Mar 2016 at 6:57pm
A Z3 is not just for Christmas - it's for life!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ruggedscot Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2016 at 8:43pm
sadly too many people are taken in by K&N - there are many sites out there that will back Mike up - the only thing that K&N seem to be able to do it make the car sound like its going harder....
 
 
Scratching the itch for roofless motoring one mile at a time....

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chopped Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar 2016 at 5:09pm
Added: Smile

The standard filter is the white one.


In its new home:


I did this because I'll won't have to change air filter for a few years & just clean it every 10,000 miles.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ruggedscot Quote  Post ReplyReply Direct Link To This Post Posted: 11 Mar 2016 at 6:06pm
See thats the way to do it - its in the original box so has all the benefits of the manufacturer set up - cool air ducting and all that. Be interesting to hear how you get on with it. 
Scratching the itch for roofless motoring one mile at a time....

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Post Options Post Options   Thanks (0) Thanks(0)   Quote martin Quote  Post ReplyReply Direct Link To This Post Posted: 14 Mar 2016 at 11:01am
I'm about to please my K and N filter. I've experienced IAT issues which can be traced back to the filter. If you Google "K & N + MAF" you will find lots of discussion. I only had the K & N replacement filter as it was installed by a previous owner. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chopped Quote  Post ReplyReply Direct Link To This Post Posted: 15 Mar 2016 at 5:56pm
Got a reply from K&N about any sensors failing and this is their FAQ reply:

20. Will a K&N filter cause my vehicle's mass air sensor to fail?

No. This is an "urban myth" and has not been supported by any factual evidence. The oil does not come off of a K&N air filter when it is in use, even when over-oiled or in extreme air flow rates exceeding 1000 CF'M.

If somehow K&N air filter oil were to make contact with a mass air sensor, the oil would not cause the sensor to fail. We have intentionally coated mass air sensors with our filter oil, and monitored the sensors' output when installed in daily driven vehicles. These sensors continued to function normally, even after being sprayed and submerged in K&N air filter oil. K&N air filter oil does not cause problems with mass air sensors. More mass air sensor information.

21. Can a K&N product cause my Check Engine Light or Service Light to come on?

It is possible that the Check Engine Light may come on after installing a K&N air filter or performance intake system. This does not necessarily mean that there is something wrong with your air filter or intake. Sometimes, the higher air flow and lower restriction provided by the K&N will uncover an existing mechanical or electronic issue with your vehicle. In rare cases, you may have a K&N product which was manufactured outside of its design tolerances, causing sensors in your vehicle to read data outside of their normal expected values. In either case, the K&N Warranty Department can work with you to narrow down the cause of the Check Engine Light and correct the issue.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chopped Quote  Post ReplyReply Direct Link To This Post Posted: 15 Mar 2016 at 5:58pm
Hi Jim,

Thanks for the enquiry,

Please see our FAQ page hopefully the information here can assist with your questions:

 

http://www.knfilters.com/faq.htm#20

 

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

 

http://www.knfilters.com/air_filter_testing.htm

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Post Options Post Options   Thanks (0) Thanks(0)   Quote MHunt Quote  Post ReplyReply Direct Link To This Post Posted: 15 Mar 2016 at 6:39pm
Why would anyone take the chance ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chopped Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jul 2016 at 8:55pm
Originally posted by MHunt MHunt wrote:

Why would anyone take the chance ?

 1) You never have to replace the air filter again
 2) May get a few more BHP 
 3) Sounds nice
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Post Options Post Options   Thanks (0) Thanks(0)   Quote roundasapound Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2018 at 2:28pm
For my E87 130i the BMWP air filter is a K&N filter. Exactly the same filter but £30 more from BMW.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike Fishwick Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2018 at 9:50am
As one who does not sell K&N filters, my view of the above is:

1) You never have to replace the air filter again - but you still have to clean and re-oil it.  From my Golf GTi experience this process must be carried out at least annually, when the oil - the filtering medium - has been drawn into the engine.  Where the stated 50.000 miles service interval comes from I cannot imagine!

 2) May get a few more BHP - due to the lower filtration level of a K&N, and if the filter was the main point of flow obstruction of the inlet system, then perhaps a couple of top-end horsepower may be liberated, but it would take a dyno run before and after to see.  In most engines, however, there are other considerations, such as inlet valve size, valve timing, and exhaust back pressure.  For example, in the case of the 2.8 litre M52 engines, the limiting factor is the inlet manifold, so no amount of K&N filters will make any improvement!  In cases where the filter is breathing hot air from the radiator, a substantial loss of power my well result, even though the optimists will claim that they 'feel' a bit more performance!

 3) Sounds nice - that is in the ears of the beholder!  The additional noise may please a particular type of owner, but I would suggest that the lower filtration rate is a high price to pay for some additional noise.  Noisey inlet systems are like noisey exhaust systems - they appeal to the immature and the deaf . . .


Edited by Mike Fishwick - 02 May 2018 at 3:15pm
A Z3 is not just for Christmas - it's for life!
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