Pod air filters... at what point is it a restriction?

[1JZ-Rolla]

So i've been trying to get onto the K&N Filters website for some actual flow data for over a week, but the website comes up with an error each time.

What i'm trying to determine is what the expected flow amounts are for particular filters.

For example, my 1JZ runs a 4" inlet K&N pod filter that is shorter than ideal (limited by space, see pic below).

Has anybody had experience with particular filters of a given size becoming an inlet restriction for outright flow? Unfortunately I don't have a dyno out the back of my place to do a back-to-back power run with and without the filter right now

Cheers
Phil

[rick q]

Can't help too much with the K&N unfortunately....... but ....

I'm running Unifilter socks on my 4AGE [150mm long 53mm I.D. 83mm O.D.] and it only picked up 1.5 hp by taking them off.

I'm changing that setup to a fabricated flat panel foam filter arrangement and sized the filter panel at 1.7 metres per second face velocity (like air conditioning filters) which suggested a piece 250 x 250 was ok for 1600cc at 8000rpm. (I'll actually be using about 400x400 to be sure)

That size [250x250] was also suggested by Unifilter - so for foam filters at least something around 1.7 metres per second face velocity would be fine.

If you can work out the area of the convoluted panels on the K&N and (I'm guessing) use a slightly lower face velocity (Say 1.5m/s) that should give you a ball park guess.

[Hiro]

Why not test how much of a restriction it is by putting a fitting on the pipe between the filter and the turbo, and measure the pressure relative to atmosphere, even if it's via a home-made waterfilled U-shape manometer