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Ignition Advance

To: "Spitfire List" <spitfires@autox.team.net>
Subject: Ignition Advance
From: "James Carpenter" <james.carpenter@jccsystems.swinternet.co.uk>
Date: Thu, 29 Apr 1999 23:22:33 +0100
Hi all,

Questions probebly more suted to the racers among you!

My current dizzy is a contact braker system, which has seen better days.  So
a while ago I got a Lucas 62DM4 distributer from a scrap yard.  This
replaced my warn dizzy which stopped it making such a large growling noise
when the power is on over 2500 rpm!

Unfortunatly the chainge in advance curve did nothing for the power, it
lacked the top end power.

Today I have found out that moss sell a set of 5 assorted advance springs,
which I could use to chaing the curve.

OK but what I want to know is what now, the electronic ignition made the
normaly moving ignition strobe dot into a completly stationery object, and
much better low running.

45D4   My spitfire
45DE4  Electonic spitfire
62DM4  Some Austin Meistro or Motego OHC thing!

OK I presume the E stands for electronic ignition, and the M signifies its a
magnetic pickup with a ingition black box mounted seporatly from the
distributer.  I believe the next incarnation of the distributer uses field
effect transisters.

So the D for distributer and is the 4 the case style or 4 cylinder.  Does a
GT6 have a 45D6 dizzy?

So is the 45 and 42 some code representing the advance curve!  I do know
that the 62 has got a softer advance curve!

How do I find out what the advance curve the distributer new distributer
has, and what the curve the old one has.  What are the weights of the metal
flys?

Is the advance curve for an engin purly in relation to the cam profile or is
the cylinder design also a factor.  Is it like you get a combustion chamber
profile and a profile for the cam, you then add the two together?




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