K&N Filter Everything you ever wanted to know

Drivbiwire

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The VW MAF sensor uses a microscopic heating element, any amount of oil or contamination causes the heating element to become insulated and overheats the electronic surfaces. The overheated surfaces (lack boundry layer air) distorts the microscopic surfaces. When the element overheats the airflow is distorted and the sensor can no longer provide accurate measurements of air flow.

The sensor works by taking a pre temperature reading, heats the air and takes a post temperature reading. The rise in temperature accross the back side sensor determines airflow.


K&N doesn't want you to see these:



People have NO idea how easy it is to determine how well their filter is performing.




For Mercedes they build in an electronic manometer at the MAF sensor that monitors the air filter and induction system for any restriction.

At full boost of 24 psi the air filter only imposes 3hPa of total restriction with over nearly 50,000 miles of use! The restriction data is stored in the ECU and is used to determine a filter service interval. Mercedes sets a maximum restriction value of 30 hPa for the trigger point of a filter service/replacement.

This is why I am such a strong propenent of using manometers in the OEM airbox to determine your filter change intervals.

What K&N does not tell you is that ANY amount of restriction will increase emissions, car makers cannot afford any increase and therfore design the airboxes to provide COLD AIR and no restriction to either the turbo or the engine.

A K&N can't improve on performance for the simple fact that there was no restriction to begin with. In fact the K&N simply introduces MORE dirt by virtue of its reduced filter area and larger average pore size as compared to the OEM filter that has over 10 times the total surface area. When you take into account that the OEM has more holes of a smaller diameter you quickly realize that the K&N is actually a more restrictive design when compared to the 80 deep Pleated OEM elements with a nominal 7 micron filtering capability.

After 10,000 mile of use on a K&N, note the fine dust adhering to the static charged filter box top.


Here is the MAF sensor removed from the above air box:



And here is the element, Installed brand new, Factory oiled by K&N!

(I put the dents in the filter to inspect between them)
 
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diesel-dave

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Ya Pete I have said this too, but there is "cult" following for K&N. But you show pictures and those are worth way more than words, thanks!
 

Dimitri16V

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my first TDI , a 99 , had a K+N since day one. after 40k miles, I never had an issue
 
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Drivbiwire

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micasb said:
Hi,

Does those facts apply to all the non-OEM filters? BMC?

Regards
Unless you are pulling 10" H2O on a new OEM filter why would you even
mess with the original setup?

The VW OEM filter will outflow a VNT23 at full bore, for that matter it outflows a 350Hp Twin Turbo V6...A tiny VNT17 or Hybrid VNT 20 is hardly a challenge for the filter system.

OEM fillters are CAI systems.
OEM Filters provide 7-15 microns of filtering capability at Maximum flow
OEM Filters are capable of 4 years 100,000+ miles of unmatched protection without having to do a thing to them.

Again, the best YOU the owner can do is to install a manometer, measure actual restriction and determine for yourself what is actually needed.

Until you hit 25" H2O of restriction the engine simply will not be impacted in terms of performance, emissions or fuel economy.
 

VWBeamer

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You ain't going to make much money pushing the stock stuff...what's the catch?
 

Mike_M

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VWBeamer said:
You ain't going to make much money pushing the stock stuff...what's the catch?
The catch is this: Drivbiwire has more knowledge about the inner and outer workings of TDI engines than most here, and that's saying something in this crowd.

He's trying to help dispel myths. I'm sorry, but your 171k miles (glad to hear you've had good luck and good fortune) doesn't trump the dozens, if not hundreds, of TDI engines that he's been elbows-deep in.

I'm not doubting that you've been problem-free, or that you've taken very good care of your TDI, but DBW's word on this subject is both accurate and trustworthy. K&Ns are bad mojo for TDIs, and you've been very fortunate to not have to replace your MAF at least a couple times.
 

Drivbiwire

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I think the point is not that anybody is selling anything just avoiding costly repairs to these great engines.

Like oil changes, saving your money and running the air filters until they actually need changing provides better protection and performance than needlessly messing with the system/component.

Even a highly modified TDI cannot outflow an OEM filter, VW simply built in too much reserve capacity to make any measurable difference.

Some people think a MAF sensor is restritive, yet when the air pressure is measured the MAF introduces no measurable resistance to air flow. The fact is that when you measure pressure differential in hPa you can see that even DeltaP measured in H2O may not be sensitive enough (a VERY good thing) in the overall picture. The fact that so little restriction is found with the OEM's superior level of filtration affords all of us the ability to focus on other areas for either fuel economy or performance hence the reason for posting this in the Performance section.

Again comparing to oil, we use UOA to validate our intervals, simple devices (my choice is the CAT manometer) allow us to eliminate all the guesswork and base our servicing on factual data. Another aspect is that when an owner sees how a filter is actually performing they are more in tune with the actual needs of their engine.

In the end it makes my job easier for diagnosing and greatly extends the overall component life not limited to just the engine.

One aspect is that the TDI's use the incoming air for multiple systems. Braking, Servo control, HVAC not to mention the 200,000 rpm aluminum compressor wheel! Providing each system the cleanest air possible vastly imrpoves the overall reliability, in the end I think we all agree that is the end goal.
 
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majesty78

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DBW, do you have any experience/knowledge about terms like outflow on airbox/filter capabilitys of Polo9n/Seat Ibiza engines?

They use way smaller box and filter element than mk4 Golf plattform models...
 

ryanp

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all i can add to this is a friend had 2 or 3 MAF Sensors in short order when using a K&N filter on his PD150.
 

Mikkijayne

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Ok so the OE filtration system is up to the job. That makes sense because on my A6 the same filter is used from the base 1.8 20V to the 4.2 V8 making 320 hp. Why is it just TDIs that seem to have this trouble though? After all virtually every modern motor uses a MAF of pretty much the same design. Why don't we hear about thousands of them dying? Especially since aftermarket CAI kits of considerably lower quality abound on ebay etc.

I bought my K&N simply because with the mileage I do it was more cost effective in the long term than buying loads of OE filters.
Ironically I don't know what effect it has had long term because the motor blew up from eating its own cam rockers, but you can't blame K&N for that :p

Edit - reading the other thread is it just because K&Ns are oiled that people don't like them? But aftermarket filters aren't oiled so are they ok?
 
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White Crow

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Oil is a cheap trick to filter air but they stopped using oil bath filters on cars 60 years ago.
 

VWBeamer

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I run the OEM filter, my post was sarcasm because I knew someone would come along and post something simular....as was my other post...sorry, guess I'm not that funny...:) BTW, i have replaced the MAP once even with the OEM filter


Mike_M said:
The catch is this: Drivbiwire has more knowledge about the inner and outer workings of TDI engines than most here, and that's saying something in this crowd.

He's trying to help dispel myths. I'm sorry, but your 171k miles (glad to hear you've had good luck and good fortune) doesn't trump the dozens, if not hundreds, of TDI engines that he's been elbows-deep in.

I'm not doubting that you've been problem-free, or that you've taken very good care of your TDI, but DBW's word on this subject is both accurate and trustworthy. K&Ns are bad mojo for TDIs, and you've been very fortunate to not have to replace your MAF at least a couple times.
 

Bob_Fout

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majesty78 said:
DBW, do you have any experience/knowledge about terms like outflow on airbox/filter capabilitys of Polo9n/Seat Ibiza engines?

They use way smaller box and filter element than mk4 Golf plattform models...
This question applies to US MK IVs also. Airbox upgrades to Euro cousins are a quasi-common thing for those with bigger turbos.
 

Diesel_Benz

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White Crow said:
Oil is a cheap trick to filter air but they stopped using oil bath filters on cars 60 years ago.
Oil bath filters are actually far superior to dry air filters. The only reasons they are not used anymore is the high maintenance and increased emissions from ingesting some of the oil. They also must be matched to the airflow of the engine, a single filter body couldn't be used across multiple engine ranges as manufacturers can do with dry filters.
 
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diesel-dave

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I just dont like the fact that dirt and dust line the box past the filter.

that crap in being ingesated in the motor?
 

Bob_Fout

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diesel-dave said:
I just dont like the fact that dirt and dust line the box past the filter.

that crap in being ingesated in the motor?
If it gets past the turbo and intercooler, yes.
 

loudspl

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OEM boxes + dry filters FTW

No need to spend the extra dough on oiled filters

Performance gains should be found elsewhere
 

Yreka

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Mikkijayne said:
Why is it just TDIs that seem to have this trouble though? After all virtually every modern motor uses a MAF of pretty much the same design.

Peek around on performance forums for different vehicle types, you might be surprised..

I used to have a Toyota Tacoma, the K&N was about as well regarded on those forums as it is here.

IIRC someone even dyno'ed the stock intake / filter VS the K&N FPIK cold air intake.. The K&N cost an extra $250 bucks and lost about 4HP compared to stock.
 

TDIJetta99

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03... Faster than yours =]
Mikkijayne said:
I bought my K&N simply because with the mileage I do it was more cost effective in the long term than buying loads of OE filters.
I typically get 60-80k from my paper air filter... the cold region filter costs about $15 to replace.. Even when I was driving a lot in dusty environments I would get 40k out of a filter...
 

original-G

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Drivbiwire said:
OEM Filters are capable of 4 years 100,000+ miles of unmatched protection without having to do a thing to them.
and where did you hear that?

i agree that the use of an oiled air filter is bad. however, are you saying you tested a OEM filter up to 100,000+ miles (in what conditions?), or are you telling me that's the factory specs for an OEM filter?
 

Jack Frost

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Drivbiwire said:
When you take into account that the OEM has more holes of a smaller diameter you quickly realize that the K&N is actually a more restrictive design when compared to the 80 deep Pleated OEM elements with a nominal 7 micron filtering capability.
I just removed my air filter from my 2009 and counted the pleats. There are 122 of them in my car. Since each one is almost 2.5 inches deep and 4.75 inches wide, that makes almost 10 square feet of media. (about the size of a car hood).

I didn't check the pore size, however since there was no dust inside the filter housing in spite of a dusty spring and 12 km of gravel road every day, they are small enough.

The pleats are corrugated somewhat to increase the surface area, to provide rigidity to the structure and provide channels for air to flow deep within the pleats. It is very good engineering.

This filter had been in my car for almost a year and I don't feel that the gasket has lost any of its resilience. Never-the-less, I believe in not waiting for a filter to start to clog and wouldn't think of putting the old one back in. For the cost of less than two litres of oil, why not change it every year regardless.
 

Drivbiwire

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original-G said:
and where did you hear that?

i agree that the use of an oiled air filter is bad. however, are you saying you tested a OEM filter up to 100,000+ miles (in what conditions?), or are you telling me that's the factory specs for an OEM filter?
The media per Mann-Hummel the original manufacturer of the elements rates them at 4 years and unlimited miles when monitored for restriction.

Early replacement DOES NOT result in better filtering efficiency, in fact you have WORSE filtering efficiency.

Changing any earlier than 30" of actual restriction or 4 years is wasting a perfectly good filter and reducing the actual filtering performance that would have been gained had it been left in the housing.

As an example:
 
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