Dully noted, but Dave, these cotton gauze filters are the #1 type used in SCORE Baja and KOH type racing. Some of the harshest racing conditions on earth. My comparison to drag racing was referencing the 'flow' aspect of the debate.
The great (informative) K&N filter debate. (here we go again)
It is with great pride that I'm able to start this conversation here today.
The purpose of this is to be informative, educational and last but not least controversial
There has been many a debate about the legendary K&N air filter with staunch arguments on both sides of the fence.
First, allow me to present some detailed instructions on how to properly maintain said filter (or any cotton gauze element type).
Then, I'll cover a case sample for further review and debate.
Last but not least I'll support everything with a short video from a man who is world renowned within the automotive industry (airflow research). When the OEM manufacturers have a problem they need solved this mans phone rings. His name is David Vizard, his level of experience and expertise is unmatched.
I know of several well respected figures who have done testing of their own in the past and those results have been repeated numerous times; here and elsewhere online. My intent is not to discredit those results in anyway. I'm merely presenting an entirely new set of facts and explanation of conclusion as to why it is the way it is and why those previous results ended up how they did.
Here's some initial food for thought: How much dirt and dust are we going to find behind this respectfully dirty K&N filter?
![Glasses Automotive lighting Automotive tire Motor vehicle Automotive design]()
![Automotive tire Sleeve Grey Wood Synthetic rubber]()
Stay tuned for part 2 coming soon!
The purpose of this is to be informative, educational and last but not least controversial
There has been many a debate about the legendary K&N air filter with staunch arguments on both sides of the fence.
First, allow me to present some detailed instructions on how to properly maintain said filter (or any cotton gauze element type).
Then, I'll cover a case sample for further review and debate.
Last but not least I'll support everything with a short video from a man who is world renowned within the automotive industry (airflow research). When the OEM manufacturers have a problem they need solved this mans phone rings. His name is David Vizard, his level of experience and expertise is unmatched.
I know of several well respected figures who have done testing of their own in the past and those results have been repeated numerous times; here and elsewhere online. My intent is not to discredit those results in anyway. I'm merely presenting an entirely new set of facts and explanation of conclusion as to why it is the way it is and why those previous results ended up how they did.
Here's some initial food for thought: How much dirt and dust are we going to find behind this respectfully dirty K&N filter?
Stay tuned for part 2 coming soon!
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I have to agree 100% with this. The K&N's filtering area is along the periphery of the intake boot, and the front has a cover. The foam filters front and sides are fully open for drawing air in. That is mostly likely why the K&N doesn't work all that well on a KLR and/or similar bikes with small air boxes.
This....
Versus this....not enough surface area to draw air from...??
Precisely, they're called 'outerwears' and they do as you say and pre filter the air. They're recommend for harsh(dusty/sandy) conditions as well as wet conditions.i think i remember in the 70's or so that K&N had Pre-wraps for desert racers and certain other extra dirty elements..
Should I post up the formulas used to calculate filter size req.?I have to agree 100% with this. The K&N's filtering area is along the periphery of the intake boot, and the front has a cover. The foam filters front and sides are fully open for drawing air in. That is mostly likely why the K&N doesn't work all that well on a KLR and/or similar bikes with small air boxes.
This....
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Versus this....not enough surface area to draw air from...??
![]()
I guarantee that if it was pulled open the surface area of that K&N is far greater than the foam.
With the foam, what you see is what you get.
The K&N on the other hand has a tremendous amount of surface area within the pleats.
For science @StarfuryTH should dissect his unwanted K&N and likewise someone measure the surface area of their foam.
We want pictures with measurements.
I'll volunteer to run the experiment if needed upon being supplied with materials.
Now we're talking
Like I said. Of the hundreds of atv/bike I get in my shop....I could count the foam filters that ive seen oiled by an owner on one had probably. People just don't do it. Lol . In cars any K&N or paper is better than a non oiled foam filter and I suspect that even fewer cars are properly maintained by their owners than Toys like bikes/atv/and sxs. Ill recommend a K&N over a dry foam filter anyday. Lol.
And oiling isn't terribly cheap or fun either. Maintaining our 20 or so vehicle fleet would just suck more in general if we had to clean, dry, and reoil.
. I see a LOT of old cars in my shop come in with a 350 or 400 CI engine, stock heads and nearly stock cam..... and an 850 CFM edelbrock. Lol. Can flood and kill them on demand if you open the secondary lol. I had a one small block with a pretty mild cam and little if any head work come in with dual 550s. Lol. Enough carb for a 9k RPM 460 or 454.Ask me about overcarburating
Even with my afr meter people won't usually let me put a smaller carb on. One can only jet and needle down so far. Lol. Adding a big carb spacer can help dumb down the issue too.
For filters, a stock engine only needs so much air. An NA engine will likely NEVER be built enough to need more air than the stock filter or air intake will flow, yet people spend millions on intakes/cold air/filters.
Turbo are a different beast. A tune (or even a different restrictor pill or some other cheat can gain 100 HP or more and more air may well be needed. Even without touching impellers or the snell itself
Id also wonder how many maf would be damaged by oiled foam. It's not so much of an issue now but back in the 90s and 00s we seen several K&N filters oil coat the maf and cause issues.
I was waiting for that to be mentioned and you are correct regarding surface area; I'd suggest that the location of the bottleneck to the flow is the problem in the case of the KLR's K&N.....but it really doesn't matter; testing has shown that it doesn't flow as much so the reasons why are kinda moot.Should I post up the formulas used to calculate filter size req.?
I guarantee that if it was pulled open the surface area of that K&N is far greater than the foam.
With the foam, what you see is what you get.
The K&N on the other hand has a tremendous amount of surface area within the pleats.
For science @StarfuryTH should dissect his unwanted K&N and likewise someone measure the surface area of their foam.
We want pictures with measurements.
I'll volunteer to run the experiment if needed upon being supplied with materials.
Now we're talking
Dave
Relic of 60s thinking - more is better. Dual carb small blocks were available from the factory, because race cars at the time running WOT 100% of the time they weren't idling were the sales pitch, and the big stacks on a dual carb intake sometimes made for something approaching decent vacuum signal to monster carb venturi.
I run a 600CFM vac secondary carb on my very warm SBF 331, despite some old school hot rodders suggesting I need at least a 750 DP. Spins to 6k just fine, with excellent throttle response despite sub-12" intake vacuum at idle
And yes, I'd expect a MAF sensor to be fouled by an over-oiled foam or K&N filter. Or maybe even an adequately oiled filter over time. Those sensors are very sensitive to contamination. MAP sensors not so much.
Exactly what I thought. those fingers full of dirt will be like skinny tree branch with a fat cat on it.
I remember at the start of Covid there was a team of Japanese or Korean scientists measured how far the sneeze droplets can float in the air before falling to the ground. The same camera used for measuring dust particles flow through the filter could be very interesting.
I just noticed that the top cover can be disassembled. How come nobody came with some kind of inverted cone. This way there will be no turbulence behind the flat cover and fix the air flow issue. 3D printing anyone?
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