Air Flow Meter

[Steve Meade]

----------
> From: avos at cochlear.com.au
> To: diy_efi at coulomb.eng.ohio-state.edu
> Subject: Re[2]: Air Flow Meter
> Date: Monday, May 05, 1997 12:09 PM
> 
>      My Subaru turbo 2.0L has a Uni-Filter cone filter. These filters are

>      slightly more restrictive than the K&N versions, as they are an
oiled 
>      foam type filter, though apparently they filter better. Mine also
has 
>      much greater surface area than the K&N versions so probably flows 
>      better anyway. This filter bolts directly to my air-flow meter, and 
>      immediately the throttle response and max top-end power of my car
was 
>      improved noticable with no other modifications done at this stage. 
>      Since then it now has a larger exhaust and more boost, and I can
only 
>      imagine that the difference of the filter has been amplified though
I 
>      have yet to change it back to standard to see. One thing I will say 
>      that is different between the Uni-Filter and K&N is that the
UniFilter 
>      has a machined alloy trumpet which they claim achieves more laminar 
>      flow by swirling the air into the air-flow meter. This may be a
ploy, 

	I spoke to soon in my reply post to Kevin. I should have read yours first.
In most BMW kits they use a basic K&N filter element and then each company
has its own adapter which attaches the mouth of the filter to the sensor. 

>      but it may support the theory of turbulent flow upsetting the
air-flow 
>      meter. The K&N filters have no such mechanism of enhancing laminar 
>      flow that I know of. The trumpet is probably about 3 inches long and

>      exponentially (approx) brings the diameter of the filter (~5 inches)

>      down to the diameter of the air-flow-meter (~2.5 inches).
>      
	There is one BMW kit which uses a K&N "cone" attached to a 6inch pipe
which goes to the air flow meter. I would imagine that your 3inch trumpet
saves space and works even better than that idea. Just curios, does your
Subaru use a Bosch engine management system with a Bosch air flow meter?


>      Adrian
>      
>      PS- I think the Uni-filter brand is Australian made though I am sure

>      there are equivalent versions made elsewhere.
> 
	Know if they sell in the good 'ol USA?
> 
=-=-=-=-=-=-=-=-=-=-=
Steve Meade
smeade at deltanet.com