m1bjr

You dont change the filter at every service normally, check the schedule?

Every three years or 27k miles.
So, you'll be hard pushed to make it pay on those grounds alone.

oxhouser

I know the service says every 27K but how do you compare 27K in dusty conditions to non dusty? or if you have a snorkle fitted it deff picks up more debris. Personnaly I would change the paper filter every year, I know the K&N is a good filter but the design is worse than the Honda so a clean OEM filter probably is as good or better than a K&N

MB

How is the design worse??

oxhouser

its a streight 90 degree angle at the base plate, the oem and the JR filter have a proper velocity curve to eliminate turbulance on the corners
I was shocked to see how badly designed the K&N unit was. I removed the paper and metal matrix from my old OEM filter then cut the K&N connecting pipe out leaving only 20mm rim left before the filter started then glued the K&N filter to the OEM base plate. not something i would recomend but I had all the bits and nothing to do for 4 hours.
if you want a reusable filter I would go for the Spoon or JR as these have a good airflow design.
if you want to test the filter for restriction get your service guy to save your old filter then remove the hard plastic section from the paper and use this as the unfiltered test rather than just the ruber connecting pipe this way you eliminate the turbulance problem and are testing the filter medium only

MB

Is your concern pressure and velocity drop or is it just the velocity, Ox?

I know on a hydraulic fluid application we specify sweeping bends in a lot of applications, for pump inlets. Where we have to have tight bends we use flow straighteners. In this case im not sure if its a problem or not? Its normally aspirated to the air demands are significantly less than FI. Also has the bends of the manifold itself to get straightened out.

Was going to suggest trying PipeCalc but not sure it does turbulance? Not sued it for a while

Not seen any detrimantal effects from a K&N on a dyno though - plus they tend to put a fair bit of work into their designs so it would be surprising.

Good DIYing htough!

oxhouser

MB
I am not sure if its actually a problem as the filter may be more than capable of flowing what the engine needs but from a design point of view its just wrong the turbulent air actualy reduces the diameter of usable inlet pipe. I did some time trials along a gradual incline using only one gear and flooring it to red line from 6000 rpm, the fastest time was with a clean oem filter against no filter so i am assuming it was the bellmouth built into the filter that made the gain. I repeated the test 3 or 4 times and it was always just slightly quicker to hit red line with the filter than without.

MB

I have been thinking of filter design of late.

I was wondering whether a good option would be to come straight out of the throttle body about 8" then sweep down at 45 degrees to a large diameter cone. You could support the cone in various ways.

Ok its exposed to engine bay heat, but a lot of Evo owners have proved on the move heat soak isnt an issue, plus you could duct some tubes from either wing towards the cone.

It might be bloody loud but you would be sure of flowing a lot of air and harldy any pressure drop.

Then again - the stock airbox with a snorkel is one of the best options

oxhouser

I might be on thin ice here with all the satisfied snorkle owners but I don't rate it, have you calculated the cross sectional area at the thinnest section (where it clears the cross beam) its 30% smaller than the cross section of the TB,
I think your idea is a good one, a rough guide is to use 13" length for a max torque @ 6000 rpm and add 1.7" for every 1000rpm you want to raise the max torque position. I don't think the ARC CIA is far away from this design, there is even a half way system that replaces the rubber pipe but still uses the standard airbox.

MB

I do agree there actually - I have a Mugen one and you can barely get your hand through it hence I am thinking of other options.

You need to be looking at total area and volume flow of the snorkel at that thin point versus the TB though I think, rahter than just cross section. But yep, it doesn't look or feel right.

K&N can supply tubing and filter heads you choose, so might be something I will play with.

I think Nigel has some interesting intake on his - but won't speak about it.

Bibbs

I had a K&N replacement cone, in the stock airbox (with the baffles cut out), and a Muz snorkle.

Cutting the baffles and adding the snorkle ment the filter got dirtier quicker.

The K&N ment I could clean and re-use it. In the 10k miles it was on the car, I cleaned it 3 times.

The combination gave me more cold air than the stock setup (snorkle), but there was no performance gain.