Like other folks have said, a PIC chip could replace this unit quite
handily.

The IC unit is connected to:

ISV (of course)
PS Pressure Switch
Temp II
Idle Switch
Hall Sensor
AC Switch

Once how much "adjustment" the IC unit does to the ISV in varying
situations, a replacement could be engineered.

Jon

On Mon, 8 Jan 2007, ------------- wrote:

> There are a few other issues.   There is a mode that increases the idle
> to a pre-determined
> amount to anticipate the extra load of the AC, and I bet the PS pump
> load is also involved.
> Also my guess is this circuit is turned off once the idle switch is
> tripped, but not at full throttle.
> Once all these factors are taken into consideration, you end up with the
> brainy looking
> think that VW made.  Hopefully  some has the time to engineer this thing.
>                   THe VW digifant  Jetta 88-92 has this built into the
> ECU, and these  are
> plentifull, and cheap.   I'm tempted to try this injection on a water boxer.
>                                                                   ERic
>
> Pensioner wrote:
>
> >Perhaps not so mysterious a design.  Your tachometer uses a pulse per unit
> >time to voltage conversion no digital stuff here nor D-A conversion.  So if
> >the transfer function of pulses per unit time  to voltage is known and the
> >desired range of ppt is known then the range of voltage is known.  A
> >comparator circuit can give you a measure of whether the voltage is within
> >the specified range.  If below then you have a signal that indicates engine
> >speed too low.  If above then engine speed too high.  Detailed design left
> >to David B or those with that sort of "bent".
> >
> >Pensioner
> >
> >Tau Beta Pi (bent), Eta Kappa Nu, Phi Kappa Phi in EE/CS,  O so long ago.
> >
> >
> >
> >
>