Matt Beazer <teseract@enchantedbookstore.com> wrote:
> I'm tempted to just go with the low-profile dual one I posted earlier and run
> some ductwork down and put cone filters low behind the headlights, just not too
> low as I'd like to be able to plow through moderately deep water.
As far as the water goes, you might be better without the filters
at the ends, let a drop-in style do the filtering right at the
throttle body. That should allow you to go longer between cleanings
since the filter won't be exposed to the elements.
I don't recall if you've got a 4x4, but if so and you are going
through deep mud or fording streams, having the drop-in style would be
nice since you could disconnect the hoses at the air can for
offroading. You'd be breathing underhood air, but at least it is
still filtered, and the tubes won't act like a big straw and hydrolock
your engine.
> Kinda pricey,
> but I don't know if a K&N drop in into a modified stock air cleaner will flow the
> amount I'd like for the plans I have for the truck.
It absolutely will. :-) With air filters, it seems like more
would be better, and that's true, but only to the point where the
medium flows the same amount as what your engine requires. I
manufacture a couple of different intake systems, and in the process
of developing them, I have done the research, run the numbers, and
have come to the conclusion that most people can actually get away
with a *much* smaller filter than they may think. There is a LOT of
marketing hype when it comes to air filters (well, when it comes to
the automotive aftermarket in general, come to think of it.) :-)
K&N's filtering medium will flow approximately 6 CFM per square
inch. They give a formula to calculate your required filtering area
which is "A = (CID * RPM) / 20839", where A is the required filter
area, CID is the displacement of your motor in cubic inches and RPM is
your RPM at max power. Note that max power will not necessarily be
the max RPM that you run your engine out to, but if you want to create
a conservative estimate, go ahead and use your max RPM.
So, according to that example, a 360 revved out to 6500 RPM would
require 112 square inches of filter. I don't recall offhand the size
of the stock GenII filter, but assuming 10" x 2", that would be a
filtering area of about 62.8 sq.in. That's a little more than half
the theoretical requirement so you might think the filter is too
small, but K&N's formula is EXTREMELY conservative.
There was an interesting test done about 7 years ago by Marlan
Davis and Westech. Using a 520hp 448ci Chrysler big block, they
tested a whole bunch of different filters on the dyno to see what
effect filter size had on power. The largest was 14x6" and the
smallest was 7x3". All filters tested within 4 HP of each other,
which was less than the dyno's margin of error; in other words, all of
the filters made the same power. The little 7x3", which, according to
the formulas, should only be good for a max displacement of 198ci,
made full power on a motor more than twice that displacement. (The
little filter actually made about 1/2hp and 6lb-ft more power than the
monster 14x6.) Unfortunately, they did not test any smaller filters.
(They only tested the 7x3" as a joke, they did not expect it to be
large enough to support that motor.) It would have been interesting
to see at what size the power started to drop off, in order to
calculate real world filtering requirements.
A bigger filter will allow you to go longer between cleanings, so
there may be some value to using a larger filter from that aspect, but
unless your filter is ridiculously undersized, a larger filter is not
going to do anything for power or torque. A filter only needs to be
big enough to flow the CFM the engine requires, and the filtering area
requirements as calculated by industry standard formulas are grossly
overstated. A standard 10x2 drop-in will easily support 500+hp.
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
This archive was generated by hypermail 2b29 : Sun Mar 01 2009 - 00:29:23 EST