[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: air filters

Glen Powell <gpowell@acacianet.com> noted and quoted:

>>> With extensive tesing we hve found K&N filters not to give more power than
>>> 1-2 HP.
>>This is true.
>>> If you want to feel the difference, remove the filter altogether and
>>> try that. You won't get a better flowing filter than none at all and it will
>>> show you how much more power you can get from a perfect flowing filter
>Removing the air filter can cause turbulence that can upset the airflow
>meter in CIS cars, so this is not as good an idea as it may sound. The
>filter helps to 'straighten' the airflow into and through the airflow meter.
>Keeping the filter in there is even more critital for good, smooth airflow
>of you duct the inlet to a high-pressure area Vs running the stock
>snorkel, >etc.
    I've done some extensive testing of the air intake/filter system on an
E36 BMW M3.  The stock system has a 5-6" long pipe (tube) leading into the
mass air flow meter (AFM).  An aftermarket company (Autothority, APE) has a
K&N kit where the filter attaches to a pipe (6" long) which attaches to the
AFM.  You can gain about 8 HP according to my measurements.  However, if
you merely attach a K&N to the AFM, you lose several HP in comparison to
the APE setup.  No air filter/no intake pipe is just as bad.  For some
reason, the AFM wants to see a pipe going into it; I thought it might be a
resonance phenomenon, but Glen's explanation above relating to "smooth
airflow" sounds like a good one.

Terry Donohue
'71 BMW 2002Ti
'90 Audi 200TQ
'95 BMW M3