tachometer signal revisted, LONG

[Nate Stuart]

Phil Payne said:
>> Audi says the tachs are the same.  Javad (and others) say that they need
>> a
>> signal based on number of ignition events per engine cycle.
>
> I don't know what car you're thinking of, but on the MAC-01 and MAC-12D
> ur-quattros and on the
> MAC-14 MC engines, the rpm signal comes from a flywheel peg via sender G28
> and is fed to the
> ECU.  The ECU provides an output signal on Pin 7 (lilac wire) that goes to
> the dashboard, the
> oil pressure warning controller, and the idle stabilisation unit.  One
> pulse per revolution.

Just to confuse the issue some more.... I had the MC's MAC11 feeding it's
tach signal into the tach on my 90q, which I have confirmed 6 ways from
Sunday does in fact take a pulse per ignition event (the 034efi IIc box
lets you play with all sorts of signals in fun and fascinating ways:). I
was getting a proper tach reading from my Mac11 off of pin 7, so I would
assume it was provding the same 5 pulses. As far as I know so is every
other turbo converted car out there, using the Mac11's,14's,whatevers,
otherwise we would be hearing of a lot of tach issues with 'simple'
conversions.

> I think anyone who isn't familiar with the system at this level oughtn't
> to mess with it.

Indeed.


-Nate
'89 90tq
http://www.newtsplace.com/90tq