Air Flow Meter

[Kevin Rutledge]

At 06:25 PM 5/4/97 -0700, you wrote:
>----------
>> I would not recommend a 90 degree turn or any other sharp turn for intake
>> air flow, especially near air flow meters, the air flow characteristics
>> change substantually with bends like that and some air flow meters won't
>> sense air flow quite the right way (Bosch's hot wire is one).
>> 
>	This is on a different note, but kind of the same. Over on the BMW digest
>(and I'm sure most performance auto lists) there is always some sort of
>discussion about intake modifications. The ongoing discussion is usually
>about those K&N "cone" air filter kits which replace the standard airbox. I
>spoke with one person who dynoed his car before and after the addition of
>one of this systems which essentially bolts right up to the air flow meter.
>The power of his hi-revving 1.9L engine actually went *down* with the
>vastly less-restrictive K&N cone. My theory is that the closeness of the
>air filter causes the air entering the air flow meter to be much more
>turbulent than stock causing the meter to fluctuate much more than normal
>and give inaccurate readings which will result in less than optimum amounts
>of fuel and thus less power. Does anyone have any actual experience with
>this? One idea to rememdy the problem involves a carbon fiber or alluminum
>tube between the air flow meter and cone to allow the air to smooth out.
>Any thoughts?
>

Actually, I tried that before and determined that I did have less power. I
wanted to know why so i did some testing and determined that it was not the
filter that was the problem, but where the filter was located.  The bosch
air mass sensors detect air flow in the center of them, but the way the K&N
filter was designed actually made the air flow around the outer edges of
the air mass sensor.  If you move the filter further away from the sensor,
with say some tubing, it fixes the problem.