[DeTomaso] Ignition Question

[Doug Braun]

Asa Jay,

You're correct that both the Duraspark and the Pertronix trigger the
coil the same way a set of points do.  You can think of them both as
"points-replacement" type ignitions.  The beauty of the Pertronix
is that it all fits down inside the distributor and it doesn't have 
points that can burn.  But these inductive type of systems poop out at
high RPM because of insufficient time to saturate the coil.  This is
why the factory performance distributors went to dual points for 
longer coil saturation times at high RPMs.

Capacitive discharge (CD) systems have a points type trigger input so 
you can use either a set of points or a Pertronix to trigger them. 
Most also have an additional reluctor type input and these can use a
Duraspark type distributor as the trigger (without the Duraspark box).
The MSD has both input types so it works with all of them.  None of 
these three trigger methods control the power of the spark in a CD 
system; they only control the timing of the spark.  CD systems not
only work better at high RPM's, they also provide hotter spark at
all RPM's than inductive type systems.  If points are used to trigger
a CD system, they will last a very long time because very little
current is passed through them.  For the same reason, a CD system is
very easy on a Pertronix and a Pertronix/MSD 6AL2 system is what I'll
be using in my MACH 1.  The other advantage of a CD system is that some
(MSD being one) can provide multiple sparks for each cylinder firing 
(below 3000 RPM) giving the ignition a chance to relight a cylinder
that has misfired.  This last feature is what makes the MSD work so 
well for a 351C.  A rev limiter (if present) in a CD system is icing
on the cake although the Pertronix 2 (I believe) also includes a rev 
limiter.  

Doug Braun
blue 73L #5505

-----Original Message-----
From: detomaso-bounces at realbig.com
[mailto:detomaso-bounces at realbig.com]On Behalf Of Asa Jay Laughton
Sent: Tuesday, April 27, 2010 1:40 PM
To: detomaso at realbig.com
Subject: Re: [DeTomaso] Ignition Question


dumb questions.....

I thought in the case of electronic ignition, something like Petronix  
or Durspark only controls a -trigger- of the spark and the actual  
power of the spark is from the coil.

In a capacitive discharge system, the points have some affect on the  
amount of charge/discharge of the coil based on how much the condensor  
charges.  But in a Petronix unit does that still hold true?

Asa Jay
(ignition ignorant at this point)