The great (informative) K&N filter debate. (here we go again)

I am looking forward to this thread. My last filter change was on my tiger and it came.oit like this...

Well to reiterate what I've said on the subject in the past;

1) filtration ability; I'm skeptical and Dodge had a bulletin about voiding the warranty if a K&N filter was used on a Cummins turbo diesel. I'm not convinced they trap as much fine particulate as a proper oiled foam filter. There have been numerous tests over the years.

BUT, the biggest reason I don't recommend them in a KLR is 2) because they flow WORSE than the stock filter and much worse than a Uni-Filter due to the metal end plate design. I've seen convincing tests on this by two well respected and well known KLR gurus, here's a link to my thread containing KLRCary's (Schnitz Racing) notes on the subject;

A lot of missunderstanding with airbox issues.
First, the screen. Airflow gains are not linear. Removing the screen with an otherwise stock KLR airbox will only gain you 2 cfm. The engine won't know the differance. However, with a heavily modified airbox, the gain from removing the screen is 8 cfm. Depending on what else is done to the engine, you may make more power. I doubt that you'll feel it, but a dyno will show it. Butt-dyno's can detect very small low rpm changes, but don't detect higher rpm changes very well at all. You'll likely not detect it, but that does not mean it's not there.
Comparing screen removal to other models is wrong, particularly with the newer sportbikes. With them, the screen often serves another purpose as well. Air distribution in a 4 cyl sportbike can be a real problem, particularly with "ram air". Removing the screen on them can cause very real losses, depending on the model. That does NOT apply to the KLR.
Same thing with air filters. There is only about 2 cfm difference from the best filter (UNI), to the worst (K&N). With a modified airbox, that difference grows to 9 cfm.
Here is the flow chart:
Completely stock - 64.8cfm
Same - Remove snorkle - 74cfm
Same - With UNI filter - 76.2cfm
Same - Remove screen - 78.6cfm
Same - Small "L" cut - 85.1cfm
Same - Large "L" cut, open snorkle area further - 92.4
Same - Remove door - 103.2
Alternate - UNI filter, No snorkle, With screen, No door, No "L" cut - 95.4
All at 2" of water, tested at 1 1/2" and 3" and averaged to 2"
To answer the larger question, how much air can the KLR really use?
....................
A stock KLR about 70-80cfm. With a good pipe about 75-90cfm. A modified motor about 90-100cfm. Having a bit more capacity than you you need will not hurt anything. The effects are not linear though. Going from 65cfm to 75cfm you will likely notice, but going from 75 to 85 cfm you likely won't.

Part of the confusion might be due to the effects of the carb shimming. Since that mod is for a stock needle, the snorkle removal serves not just to add air, but to lean out the top end. The stock KLR till 07 is rich on the top. ( The 08 has a smaller main jet.) Airbox mods have much more effect on top end mixture, so, with the stock needle it also helps straighten out the fuel curve.

Finally the airbox door. You've got to carefull there. You don't have clean air there. It's flowing past that door when riding. You can easily create a partial low pressure area there, depending on wind direction, and where you place your leg!

Cary"


I do not recommend removing the backfire screen (PITA) or running without the airbox door for reasons that should be obvious.

Though a KLR isn't going to have a bunch more power no matter what you do, a KLX kit combined with the snorkle-ectomy and L mod or 4 - 1" holes will have it running properly. don't bother with the little 1" foam filters if you drill the holes - they are useless.



Given all of the above, I'm not sure why a person would bother switching from oiled foam to K&N; even IF you believe it filters as well and disbelieve the information on flow, what is the advantage? why bother?

2 cents,
Dave

Br549rick said:

where can i see what kind of dirt gets through these filters??

Click to expand...

Here.
Below is an ATS 088 turbo I bought used. It required a complete rebuild, mainly due to the K&N filter that was run on it.
As you can see, it chewed up the compressor wheel pretty bad.

Another reason why many fleet companies no longer recommend the “million mile” K&N filter.
Junk I tell ya!

All of the above comments are valid points and well respected.

The above comments about maintenance intervals in relation to filtration are on point.

Where folks run into issues is during the practical application of said maintenance which in turn causes damage to the element, typically going unnoticed by the operator. The damage begins once the filter is put into service.

Let's look further into proper maintenance here:

When maintaining the filter you'll need a bucket with clean water and some K&N cleaner.

(The water already looks dirty because in this picture I've already sprayed the filter with cleaner which causes dirt to instantly start running out of the medium and some had dripped into the bucket, no problem)

Once you've liberally sprayed the filter with cleaner (must use K&N cleaner, do NOT use any other type of cleaner or soap) I usually let it soak in for a few minutes at least (not terribly long).




At this point you're now ready to begin 'dunking' the filter as seen here:

Lifting filter and dunking it repeatedly(more dirt comes out each time)

After a dozen or so dunks it should be looking clean like this below


Typically at this point(above filter) I will dump out the dirty bucket add fresh water and dunk the filter a few more times just to rinse out any residual cleaner/dirt.

Next it's time to dry:

IMPORTANT: do NOT use any sort of compressed air to dry the filter. It MUST be left alone to "air dry". This step is where 90% of damage to the filter occurs from. Using any other method except open air drying causes separation of the cotton fibers, in turn, causing a condition known as a "blown filter" once this happens the filter is no good and must be discarded. (Don't be that guy).

Choosing to oil and use a "blown filter" most likely results in fine dust ingestion. (Hence the black looking substance coating the surfaces of the intake tract and or turbocharger compressor blades)

Further on in this article we will talk about how a K&N filter actually works to remove particulate from the air.

Once the filter is dry you must re-oil with the correct K&N filter oil. (Do not use any other type of oil, period.)




Additionally, I'll be posting a video by Mr. Vizard addressing the flow aspect of the debate. (You'll be quite surprised at the results)

Next: we'll look at the filtering capability and what this filter trapped. We'll also have a look at what this filter looked like on the inside before it was cleaned. Stay tuned coming soon.

I want everyone to chime in with their thoughts and experiences.

Once the filter is sufficiently dry I apply a liberal coat of fresh K&N oil. Inside and out. It should look something like this when finished (sufficiently saturated but not soaked)

If it looks as though you just pulled it out of the package for the first time then you're on the right track.