KN airfilter does it worth it's price?

Years ago when I worked for a construction company, we did earthwork so lots of dust, a rep for a company that had washable reusable filter elements pushed our service manager to try the units for a cost savings over the paper elements we were using. I understand this is an apples to oranges kind of comparison but it points out another side of the air filter debate. The machine I was running had a vortex style prefilter intake on the hood,similar to this 51QeC1IMKFL._SL1000_.jpg no filter element but it swirled the intake air and the heavy dust was separated out before getting into the engine, This was followed up by a large paper filter, followed by another large paper filter. The normal procedure on a dusty job site was the operator would dump the vortex as needed, sometimes as much as twice a day but usually it could be left for the service guy after hours who would dump it and blow it out with compressed air, He would then pull the first paper element and clean it out with a combination of tapping it on the machine to dislodge the dust followed by compressed air from the inside to blow out what was remaining. This could be up to a 15 minute process for cleaning the 1 element. The second paper element got checked daily but rarely cleaned as the first one caught the dust.

We replaced the first paper element with the reusable washable unit to run the test and after the first day it was scrapped because the second paper element then needed to be cleaned like the first one had before the test. So from this experience I only run the k&m type filters on cars with engines I don't care about. Now for our application on the street I'm not sure how much dust is going to be ingested into the engine and just stopping the gravel from getting in may be enough but I'll stick with a paper element and if I need more flow I'll get a bigger paper element.
 
Dr.Jeff said:
One factor that is easily overlooked is what's the maximum flow the particular engine (for a given application) can require under peak performance conditions. As a simple example, let's say a engine's design is such that at peak performance it requires a maximum air flow of 500 CFM. So long as the air filter can pass 500 CFM there is nothing to be gained be using another filter than can pass more than that. And that was the point of previous tests; the stock air filter flowed more than the engine's maximum requirement, so replacing it with any other filter offers no benefit (performance wise). However if that replacement filter offers a lower level of filtration, then there is something to be lost by installing it.
Click to expand...

What may be overlooked is it is not just the increased cfm due to lower restriction. It is the pumping losses to pull the air through the filter. It takes work to do. So if the filter is “is more free flowing” it takes less work to pull the air through it. Think about it like a lighter flywheel – it doesn’t make more torque it reduces the amount required to rotate it thus giving that torque to the drive train. Another way to describe it may be to think of drinking a milkshake through a straw. You feel the resistance to do so. If the straw size is increased, the resistance is reduced – less work.
 
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@Brad Garska is exactly right and it gives the sensation of better throttle response. In theory the top speed could increase as well especially with a carb engine since it is not restricted by the barn door on the airflow meter and fuel injectors.

When I originally was thinking about a K&N style filter it occurred to me that Bosch always had a restrictive intake on the filter box of any system that has our style airflow meter. I believe the reason is to prevent the airflow meter from getting too much draw at once and flipping wide open then bouncing closed etc.. Instead the large canister acts as a small reservoir to open the airflow meter quickly but then the small intake on the canister restricts the flow enough so the airflow meter moves slowly...

I opted for using the K&N filter that goes inside the stock canister...

Ed
 
This is why I like this forum. From one innocent simple question You can get a lot of great answers with explanation.
 
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