Forwarded: Re: Ignition timing reference points

[RABBITT_Andrew at mv8.orbeng.com.au]

nissan use a 360 tooth optical encoder mounted in the dizzy on some of 
their 6-cylinder models (not sure which ones though) which would give 
you 2degCA resolution.

From: EAXMJHI at ean2.mecheng.nottingham.ac.uk:smtp
Date: ## 10/08/96 17:01 ##
> From:           Kalle Pihlajasaari <kalle at device.data.co.za>
> 
> I was thinking of adding a 256 or 360 slot optical interrupter disk into
> my distributor to give double the that number of edges every rev 
> of the dizzy (or the same resolution on the crank).  Is one degree
> on the crank accurate enough for a totally digital one or two of
> design for a mapped ignition.  Interrupter disks like this are
> available alone and have usually got an index mark at another
> radius.  I could then just replace the cam section with a nice
> shaft without the centrifugal advance (will the rotor still point 
> close enough to the correct cap electrode if the rotor is not
> advanced at all and the timing is ?
> 
> Just a few thoughts.

This is far more than enough for a digital system.  Most systems 
these days use a 36 tooth wheel with one tooth missing to signify 
TDC.  With the computer it is possible to get accurate enough timing 
form this.  360 teeth would provide so much information you would 
need a faster processor to keep up.

Martin