At 09:14 PM 1/20/2002, Larry Alofs wrote:
>It seems to me that the resistances in the AFM are around 1K. With a
>capacitor of 10 MFD you get an RC time constant of .01 seconds, with 20
>MFD about .02 s.  It appears that we could go to 50 or perhaps 100 MFD
>and the signal would still change fast enough to follow the movement of
>the vane in the AFM.
>  Whaddaya think?

Seems possible to me.  Assuming  1K-ohm, and 5*RC for essentially complete
response, that would give a tenth of a second for 20 uF, up to a half
second for 100 uF.  I have the feeling that half a second is pushing the
envelope a bit, but it's just a feeling -- and you get 95% in 3*RC.  The
system has to be able to respond, for example, to the overswing of the vane
when you open the throttle quickly (provides enrichment analagous to a
carburetor acceleration pump).  Watching mine idling, I have a feeling that
the vane oscillates at around ten Hz, but I'm sure the system doesn't want
to know that (and it's a while since I've watched it, could be off by
factor of two).

Best I can say is it doesn't sound outrageous, why not try it and see what
happens.  I would recommend stopping short of those cute little 1-Farad
caps from Panasonic, though.  <g>

david

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"