I agree about the fleet use.
How many Duratec rental cars are out there. I would imagine most are Zetec...
The cotton/wire mesh straightens out the incoming air as opposed to the foams basically trying to stop it altogether (turbulence) this is where it makes a jump in CFM difference. Plus the air has less turbulence so it increases velocity and efficiency.
K&N has achieved over 99% efficincy rating. Like I said. You can fight over that last 1% all you like. Yes foam can hold more dirt. But the CFM rating of foam plummets extremely fast and it's pretty low to begin with (I gave specs in the Filter 101 post)
The CFM rating numbers were SAE.
K&N's numbers are a bit more skewed against foam & paper...
The test they showed had: (all indentical filter applications 12" round x 3.4" tall)
AMSOil LT-31 Foam: 376cfm
Dirty K&N: 463cfm (used 42k miles!)
Paper: 508cfm
clean K&N: 887cfm
That's like 236% more... That's seems pretty high. I'll stick with the 50% SAE numbers...
It would take quite a spirit washing to disrupt the layers of cotton and mesh to effect the filter efficiency greatly. (like compressed air! that's a no-no BTW)
Oh yeah. BTW - I've cleaned mine twice and those are my sample results. (matter of fact that sample was the oil change right after I cleaned it. When it is at it's worst efficiency) I live in KC. Probably slightly above average dust conditions.
I'm glad you like your foam. I like my CFM. I do not have a filtration problem. I am happy...
