tachometer signal revisted, LONG

Alan Pritchard apritchard at seaeye.com
Tue Dec 2 06:35:34 EST 2003

I think that's one of the major differences between the turbo cars and NA,
the mac ecu's use a  flywheel sensor for more accurate timing, while the NA
cars stick with timing info form the dizzy, which due to cam belt slop, and
even torsion on the camshaft produce a less accurate engine position
 -----Original Message-----
From: 	Phil Payne [mailto:quattro at isham-research.com] 
Sent:	02 December 2003 11:30
To:	quattro at audifans.com
Subject:	Re: tachometer signal revisted, LONG

> 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.

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

  Phil Payne
  +44 7785 302 803

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