Re: RE: What can MPI do?

From: Klaus Wilkens (
Date: Tue Jun 16 1998 - 21:09:49 EDT

The MSD puts out a very short duration high votage spark, the duration is short
enough that it puts out multiple sparks at low rpm. As RPM increases the window
available for the spark narrows and the multiple sparks disappear. The time
constant to charge a capacitor is 5 times the capacitance in farads times the
resistance in ohms. In order to charge the capacitor quickly enough for the
multiple spark they have to use a low capacitance which leads to a low energy
level and when the engine raches the speed where you are limited to a single spark
you are attempting to fire the mixture with a low (relatively) energey level. wrote:

> In a message dated 98-06-09 14:17:33 EDT, you write:
> << > but I have yet to hear from anyone on the DML who has not experienced a
> loss
> > after installing an aftermarket ignition.
> ets are subject to many variables >>
> I put the MSD on during the winter (tried to use it last test and tune but the
> retard box was bad (eventually found that out) so went back to stock and
> installed during off months) went back to racing in the spring but was 2 to 3
> tenths slower than fall, Lots of variables as you say but also noticed less
> power (speciifically on a regularly traveled hill) and got to thinking that
> the only real change was the MSD. I went to the track made 3 runs with MSD
> unhooked it made 3 runs stock and then repeated the process again.
> Consistently with MSD hooked it was 2 to 3 tenths slower. I tried again in
> another week, same results. I now have a switch and relay set up to switch
> between stock and MSD other than the Blaster 3 coil runs on both. A couple of
> times when done racing I forgot to switch it back and always get reminded when
> I get to the hill. With MSD 99% of the time it will down shift on the hill
> with only me in the truck. With stock 99% of the time it will pull the hill no
> problem without shifting down even with 2 people ???????????????????????????
> What would you think about this test???????? Pretty clear cut to me. Why, I
> don't know I called MSD and they told me to unhook the Computer for several
> minutes and let it relearn with the MSD, I did that several times, same
> results.. I do use it with the NOS to retard the timing (only when the juice
> comes on) to be able to use MP computer for raised rev limiter and it run
> pretty good but I would like to try the stock computer with a rasied rev
> limiter and no MSD. I had run a 13.33 @ 103 with the stock computer and no NOS
> and street tires. With MSD and BFGDR's and pulleys best run 12.95 @ 104 ???
> What ya tink ??
> Bill

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