Miata Mailing List: September 1998, Message #257

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> Previously on MSD vs J&S, Steven Daniels <stdaniel@mindspring.com> said...
> 
> > Can anyone explain the differences (practical and
> > fundamental) between the MSD and the J&S knock
> > sensor?
> 
> The MSD retards timing by a fixed amount proportionate to something (boost
> level?)  I think it's MP controlled, but I'm not sure.  The J&S is a knock
> sensor which listens for knocking and then retards the spark until it
> stops.  I assume it advances it again at some point, but I don't know
> exactly how it works as I have neither system.
> 
> The long and short of it is that the J&S responds to a problem, whereas
> the MSD tries to prevent it without being able to detect it.  The J&S will
> allow more advance to be safely run than the MSD.

I think (but not 100% sure) that the MSD retards all the cylinders by the
same amount, while the J&S can and will retard each cylinder
individually...

Tony Schreiber, Senior Partner              mailto:dune@technocraft.com
Man and Machine, Limited                    http://www.technocraft.com/
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