Kyle Kozubal <solocamxt@sbcglobal.net> wrote:
> Concerning the K&N FIPK II.......
> Has anyone removed the heatshield and installed a
> larger filter?
> The heat shield seems almost pointless and the stock
> K&N filter (RC-5040) that comes with the kit does not
> flow enough CFM.
Actually, that filter should be plenty big enough. Speaking
strictly from the perspective of effective filtering area, and based
on K&N's published spec of their filter medium being capable of
flowing 6.03cfm per square inch, and assuming a 4.7L V8 which peaks
around 4700rpm, the RC-5040 filter you mentioned is over 4 times
bigger than it "needs" to be. In fact, assuming the same 4700rpm
power peak, that filter would be capable of supporting an 1191ci
(19.5L) inch motor.
The above assumes that I did my calculations correctly in coming up
with an effective filtering area for that particular filter of 268.62
square inches. This is an oval tapered filter so what I did was to
calculate the circumference of the top and the circumference of the
bottom, then I averaged those two together and multiplied it by the
height. (Note that you need to subtract 3/4" from the height to
compensate for the sealing material and rubber seals on the top and
bottom.) Here's a link to the filter specs in case anyone wants to
check my math: http://www.knfilters.com/search/product.aspx?Prod=RC-5040
The above info about how much filter you need for a particular
motor is based on K&N's published formulas, however I have discovered
that those formulas appear to be very conservative. The best example
of this is a dyno test that was done by Car Craft magazine in their
April 2002 issue, where they took a Chrysler big block and tried a
bunch of air filters on it, from a 14x6 to a 7x3. (These were open
element style air filters, so those dimensions are diameter x height.)
All air filters tested came within 4hp of each other on a 520hp motor,
which was actually smaller than the dyno's margin of error. The
smallest air filter made the same power (more, actually) than the
largest, depsite being less than half the size it would theoretically
need to be to support full power on that motor.
Your only actual benefit to installing a larger air filter will be
an increased service interval.
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
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