Date:         Fri, 20 Apr 2001 14:39:30 -0600
Reply-To:     Blake Thornton <thornton@MATH.UTAH.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Blake Thornton <thornton@MATH.UTAH.EDU>
Subject:      Timing theory
Content-Type: TEXT/PLAIN; charset=US-ASCII

Ok, I'm confused about timing and getting the sparks to fire exactly at
the right moment.  The only car I have a vague understanding of is my 84
vanagon, but I have lots of questions.

What determines when the plug fires?  I had thought that when the
distributor rotates and makes contact with the cap, then this is exactly
when the plug fired.  But now I read what David wrote and he said the the
digifant engines the ECU controls the timing (i.e. the exact moment of the
spark) and the distributor mearly points to which plug is going to fire.

So, now I'm confused.

Also, in my 84, I think can adjust the timing by rotating the distributor
around.  I thought that this would change the the firing point.  I thought
that the timing was adjusted in the digifant engines exactly the same way,
but if the ECU controls the timing then there must be something different
going on here.

And, how about advances.  My 84 has a vacuum advance built into the
distributor, does the digifant (I guess I could look in the bentley).  How
about the centrifugal advance (which I think advances for higher rpms and
is also built into the distributor)?

And finally, surely there are cars without distributors.  Do they have a
separate ignition coil for each cylinder?

thanks,
Blake
84 Westy Vanagon

I put in the vanagon so that this would make it through to those of you
filtering mail with this word in it :)