DangerMouse:
Yes, I have an open mind and absorb all performance car info like sponge (a lot leaks out, but I try).
The theory is nice, but real life is different. The flow #'s are based on 1.5" of vacuum, a normally aspirated engine does not draw that much, so all those # are based on an error. The 1.5” number is used because it’s easy to work with for testing cfm, much easier than say 0.1”. Vacuum means there’s a restriction, restriction means power loss. If you’re running vacuum at full throttle then you need a bigger carb, efi, filter or whatever.
Btw, a well designed smog engine may have 80% efficiency, but not a performance motor. Not that 80-100% is a huge difference, but 1.5” vs 0.1” is.
I don't agree with your forced induction and heat theory btw, I didn't make sense. Not insulting you, just doesn't make sense.


89-300ce:
Yes, I do run a prefilter, but again it was difficult to find one that didn’t kill flow and power. Mesh and typical foam like those used for dirt bikes are too restrictive; once again I found the solution from K&N. The prefilter is open foam, the cells are huge and flow nicely. I use regular K&N oil, not foam filter oil. It’s really amazing how well K&N filter oil works, The prefilter can literally be backed in oily sand, yet the cotton filter is 99% clean. I can only guess the cotton filters out 99% or more of that remaining 1%. Oiled cotton can catch smaller particles than any dry paper filter, just like an old oil bath setup.

mctwin2kman:
You need to tune your car to run with the increased airflow of a K&N.
I have a K&N in my 190E too, but it runs fine either way.