Ignition Book

[Zublin, Bryan (SD-MS)]

I have measured the frequency of the multiple spark.  If I remember 
correctly, it occurs at a rate of 1 mS between sparks.  At low engine speeds 
(cranking to start engine), it will fire 10 times or so.  At about 2500 rpm, 
it only fires once.  This is for a 4 cylinder.  Cut all rpms in half for a 
V8.  So, the advantage of multiple sparks is lost pretty quickly.  Use two 
MSDs and multiplex them to regain the multiple sparks at higher rpms.

I promised a set of schematics for the MSD 6A a loooong time ago, and am 
very delinquent on getting this out.

Bryan Zublin
bzublin at gi.com
 ----------
From: owner-diy_efi-outgoing
To: DIY_EFI
Subject: Re: Ignition Book
Date: Friday, September 29, 1995 2:40PM

> MSD ignitions are also CD, but the added multiple spark is something
> the others (like Jacobs) do not have.  They both put about 450 volts
> across the coil, using a DC-to-DC converter.  MSD also does not
> "pot" their boxes.

What is the frequency of the "Multiple Spark"?  At really high RPMs, the
multiple spark may not even be an advantage, since combustion happens so
quickly.  Has anyone out there looked into this?

Larry Harris  lharris at crl.com  (770)682-8842 (voice)
'86 Mustang LX 5.0 Coupe (152K)  '82 BMW 635CSi Euro (122K)
Meyers Tow'd Dune Buggy (1776cc) '83 Toyota Tercel (185K)