----- Original Message -----
Sent: Tuesday, April 19, 2005 7:59
PM
Subject: [FlyRotary] Re: Area calcuation
for Cone air filters was [FlyRotary] Re: Air filters
Rusty, some of the cones have an opening on
the intake in and another smaller cone that is inside the large cone for
increased filtering area. They don't specify the dimensions of this
inner cone so I conservatively just make it 10% of the total filter area of
the larger cone.
That makes sense Ed. I later saw what they
called an inverted top that had that sort of arrangement. With
the size I could use, I don't think there could be much of an inside
cone.
That filter should give you approx 352
square inches of filter space. For a 13B at 7000 rpm K&N area
calculation says 53 sq inches is sufficient, so yes, I think I can safely say
you have more than enough filter area. So thats good as it will give
more filtering and less airflow obstruction.
I have to admit that I'm still having trouble with your
spreadsheet. When you calculate 53 sq inches using their formula,
this seems to indicate that you need 53 sq in of "filter element" surface
area. It looks like they're assuming all their filter
elements to be the same thickness by eliminating that parameter. From
that standpoint, I think you can drop the X4 factor to estimate the
pleat area, because they've already built that into their recommended
area formula.
Well, you could be correct about that - but they do
not explicitedly state that fact. However, since they do infer that you
should look for one of their filters of comparable area - I can understand
someone viewing it that way. But then they nowhere give you the filter
area of their filters (at least not the cone ones). I'll blame it on
Jerry for bring the accordion pleats to my attention
{:>)
Anyhow, you's gots your choice, The formula
first computes the area of the truncated cone, if you feel that already has
the factor of x4 in it then you get their area and can disregard the X4
multiplication I do.
If all we care about is the filter element surface
area, then your "filter area" (i15) seems to give the number we need to
compare to their formula. This would be assuming that you have one of
their more normal filters that doesn't have the end open.
Sounds reasonable to me Rusty. In anycase, I
think this gives you a somewhat better idea than a wide A__ guess
{:>)
Back to the filter I had mentioned, 4.5 base x 3.5
top x 5.75 length. In their sizing info, it appears that they want you
to reduce the height by .75", because the ends of the filter are sealed in
rubber, and don't pass any air. That makes my example 5" tall.
using those numbers, I get 63 sq in for filter area. Since I will run
7500, that makes the requirement 57 sq in, rather than 53. Sounds
like it will still work up to about 8200 rpm, which should be sufficient
:-)
You are undoubtedly correct, Rusty, but I think we
are the point of marking with a paint brush and cutting with a chain
saw. This should put you close enough.
Heck, I'll order one and see how it works. Easy
to test on the ground before going to the trouble of making
a box for it to live in.
I'm looking at a
filter made by S&B, they have a base which is shaped more like a funnel
than a square end which should help the air turn better from the filter to the
intake. Its call Absolute Air Flow AAF and is used with the cone
type filters.
Ed A
Rusty
(almost deleted this since it was getting out of
control)