Originally posted by Six Banger
FWIW, I service quite a few street motorcycles(sportbikes) with K&N filters and always see dirt in the throttle body/carb opening that has obviously gotten past the filter. Take a new oiled K&N out of the box, then hold it up to the light, look through the filter media and you will see lots of light. To me that means spaces for dirt to go through, but good for airflow. This is the reason in severely dusty conditions K&N suggests a "pre cleaner", which is oiled foam that goes around your regular filter. Oiled foam is used for motorcross bikes to this day for a reason. It flows well and traps dirt the best that I have seen. I think people (automotive) dont use it so much because of the "servicing" aspect
I read that little diatribe on the filters and it seems that the one thing that holds is that the more circuitous the path[labrynth effect],the better the dirt gets trapped.
Makes perfect sense.
However,to a large extent,that will also limit flow.
It's just a matter of how nasty the operating environment is that the filter has to live in.
On a motorcycle,you've got the front wheel kicking up dust almost directly at the inlet filters.
On a car,the filter is shielded behind the bumper at the very least.
No filter is perfect,if they were they wouldn't breath at all.
BTW,I've looked through all sorts of air filters at the light and I can see through all of them.
Nothing new there.
As a matter of fact,I used to check my paper filters that way.
However,your pointers on severe duty filtration are appreciated.
Maybe some of the guys on dirt roads in the sticks will take proper note.
Good info.
