ignition reference

[Kalle Pihlajasaari]

Hi John,

> My experience is that one is more likely to build a robust, high 
> quality timing disk with six or eight accurately spaced notches or 
> vanes than one with 360 or 256 notches and I do have access to 
> numerically controlled equipment.  It is far better to improve the 
> quality of the inputs than to depend on many more, less accurate 
> inputs.  Quantity certainly does not imply quality in this instance. 
> The most precise measurement you have available in a typical 
> ignition system is the record of time in a 16 bit counter.

I would never have even tried to make such a disk (unless sending
it out to be laser cut, quite cheap these days :-)

A sealed encoder is what I had in mind for line counts like that.

> If you divorce you mind from  thinking in terms of degrees advance 
> and instead consider ignition TIME before TDC or some other datum, 
> ignition calculation is much simplified.  The time advance bears a 
> near inverse linear relationship to manifold pressure. It is the 
> different rotational speeds that make calculation if the ignition 
> position touchy.  

No manifold but I get your point.

Cheers
-- 
Kalle Pihlajasaari     kalle at data.co.za
Interface Products     Box 15775, Doornfontein, 2028, South Africa
+27 (11) 402-7750      Fax: +27 (11) 402-7751