On Sat, Feb 7, 2009 at 4:07 PM, pdooley <psdooley@verizon.net> wrote:
> Probably discussed before, but the *real* fix is to replace the AFM with a
> MAF.
> Figure out the output signal profile of the AFM and build an interpolator to
> plug into the MAF.

One of the guys at Bostig mentioned investigating such a device once.
Trouble is, "hot wire" air flow measurement basically combines  intake
air velocity, temperature, and pressure and reports them as a single
value to the ECU. This is fine if the ECU is designed to use that
value, but it gets messy when you try to apply it to an ECU like the
Digifant, which reads air temp and (velocity/pressure) as two separate
values. It would require a pretty gnarly lookup table to "unbake the
cake" and get the two values out of the single hot wire value, and the
only real way to build that table is with hours of work at a flow
bench rigged to feed air at a wide range of temperatures, followed by
probably twice as many hours tweaking the system on the engine to get
it refined. In the end, it'd have to be something some nutter does out
of sheer personally folly, rather than a kit someone designs with the
intent of making money. I once sketched out a plan for doing it, but I
can't even find the time to fix the bad oil cooler O-ring on my '90 GL
that's been sitting for 5 months, so that plan resides in a folder on
my computer, right next to the Atmel microcontroller pseudocode I
wrote up to digitally mimic the analog Idle Control Module....

--
John Bange
'90 Vanagon - "Lastwagen"
'90 Vanagon GL - "Wiesel"