In article <email@example.com>,
> First, this is born out of a "mental exercise" between the parts boys
> and myself...about the merits of K&N air filter...filtering efficiency
> withstanding, they are being marketed on the sole concept of CFM at the
> local parts store.
> How would one figure the CFM required at some RPM for an "X" liter
> Would it consume "X" Liters every 2 revolutions? (4 stroke,
> up/down/up/down - so one time it goes down it will be due to the
> combustion stroke not intake...right?)
> 1 liter = 0.0353 ft^3 (man, can't imagine cramming 30, 2 liter
> bottles in a 1 foot cube box!)
> So would this be correct? (Liter) * (RPM)/2 *(0.0353) = CFM
> For a 2.3 liter motor with a Red Line of 8000 RPM:
> (2.3)*(8000/2)*(0.0353) = 325 CFM
> Just trying to determine if anyone really needs a K&N air filter that
> claims 450 CFM (in this case) - especially since most people don't
> generally drive around at the Red Line!!!
Unless a filter is severely restricted the only time flow is affected by
anything other than the restriction forced on the system by the throttle
plate is at wide open throttle. If you have determined that the intake
air flow is insufficient to provide satisfactory performance then you
will have to do some serious elargement of the throttle housing diameter
coupled with intake runner improvements (both length and diameter,
interior surface preparation-streamlining and proper surface finish to
enhance turbulence for rapid fuel vaporization and so on). If you just
want eye candy K&N is the way to go--the kits are pretty.
K&N filters have captured the fancy of many enthusiasts through clever
and effective advertising. The one caveat I've found is that cleaning
and oiling the filter must be done very carefully. Any excess oil that
is drawn into the inlet piping will eventually deposit on the hot film
or hot wire of the mass airflow sensor. Even though the burn off cycle
for the sensor occurs after every shut down when the motor has exceeded
about 2000 rpm it is inadequate for vaporizing the oil that lands on it,
unlike the dust particles that it was designed to eliminate. This
ongoing accumulation of varnish on the hot film or hot wire will cause
premature, expensive failure of the part.
The goal when driving is to miss the maximum number of objects.