Cone air filter measurements?

[rwh11385]

From someone's air intake thread, it was brought forward that the panel air filter has more surface area than a cone.

I wish I could measure my panel.....but my car is not yet back to me, hopefully tommorrow. But I am curious on what size your guys' cone air filters are.

Someone measure the 325i 's panel filter, and then whoever measure the length of the cone and the diameter, and whether or not the end is open or closed. Then it's simple geometry to find surface area.......

But if the panel has more surface area, the "Porsche Motorsport" or "Cheese-grater" mod might be the best, while also cheapest intake mod.......

[Sean]

Crap, shoulda posted this yesterday, I swapped my K&N Panel filter out of our 87 325, and put it in my Super Eta. ;)

Since I already have the K&N panel filter, I'll probably do that intake mod too. Seems like the best way to go.

[rwh11385]

Can you measure it today? I want to know the "standard" or "control" surface area for the air filter......

[Sean]

The surface area of a normal air filter? Or, how big the box is?

Cause, i could get both. ;)

[rwh11385]

yep, that's all I need. based on what other say, the stock air filter flows MORE than aftermarket cones. If you could provide the stock airbox/filter size that would be cool.

I just wanna see the #'s.....of course there are different sizes of cones.

[Sean]

Ok, I'll see if I can get a chance today. 8)

[rwh11385]

I'm pretty sure I have the surface area for a cone filter. Jay (mystical) gave me the measurements of his cone: 6" wide at base, 3.74" at end, 6.5" long......

I used calculus to find the surface area. Just like volume by discs, I took the integral, but instead of the area of each disc, I found the circumference. So it was the integral from zero to 6.5 of 2(pi)(1.875+.1739769X)......which came out to be 99.5 sq in.

Maybe someone could check my math, I did it rather quick. But I'd like to see how that compares to the S.A. of the stock filter..

[JRowe]

The surface area of each brand of filter will differ greatly. You have to factor in the number of pleats and the depth of the pleats. You can't simply compare panel to x sized cone without digging deeper.

[rwh11385]

Yeah, I know. Each fold acts like a villa in the small intestine, which therefore increases the actual surface area. But I'm just looking to compare the "flat" surface area right now. Er, that is, ignoring the pleats. May be a rough rough estimate, but gives one some idea.

http://www.bolhuijo.com/airflowtest/

K&N boasts on their website that their filter media flows 50% more air than an equivalent area of paper. With 18 pleats each .7" deep, the area of this filter is 202 square inches. That's less than one seventh of the Mahle filter area. I'd say the cotton filter media flows a lot better than they claim.

Along with pleat and the additional surface area issues, thereis also the K&N claim it flows 150% of what paper can changes things up again.

Bottom line, I am trying to track down if cones flow better or worse than stock E30 325 filters......hmmmm

hmmmmm........

of course, a huge ass air filter won't do much good regardless if it is just on the stock motor....... i mean the AFM is the bottleneck right? not the air filter........