Dwell Control

[Bruce Plecan]

----- Original Message -----
From: G. Scott Ponton <gscottp at ix.netcom.com>
To: <gmecm at efi332.eng.ohio-state.edu>
Sent: Friday, April 16, 1999 2:09 AM
Subject: Re: Dwell Control


> Back to the problem with using a SY/TY bin with a system designed for DIS.
>     All of my notes tell me basically the same things. All of the control
> signals between the ECM/PCM and the ignition system are the same between
the
> HEI and DIS style systems.

If they were then, it would be a Plug+Play deal, and it's not..

Although there are 2 different variants of the
> DIS system and 2 different HEIs.

Lots more variants then that ie
DIS
can use hall sensors
can use reluctor sensors
can use a combination of the above
can be "Northstar" type
(could include coil per cylinder types, also)

HEI,
reluctor
optispark
reluctor/hall

 The differences seem to be the same for
> both systems in that each one has a fuel sync generator of some sort in
> order to work with SPI. In the HEI system there is an aditional hall
effect
> IC built into the distributor which generates the fuel sync info.

What HEI module does a Sycn signal (not DIS type)?.

>  The only exception is the opti-spark on the
> LT engines. This system is more or less parts of both systems used in such
a
> way as to integrate the major part of the ignition operation into the PCM.

I don't understand what leads you to say the above..

> In this system the module is basically a simple switching device for the
> coil.
>     OK background info finished. On the the other problem. At this point
it
> becomes a magor problem too!! After careful though I think the problem
that
> is occuring has to do with the operational software for the SY/TY ECM.
There
> is something missing in a HEI system. It is missing a sync pulse. It's not
> needed for the HEI system as the timing and position of the HEI determines
> which cylinder gets the spark. The DIS system is more or less self
contanted
> BUT.................. a very large BUT here. The computer ( more
conjecture
> on my part from here) probably receives a sync pulse in the reference
signal
> from the ignition module. It then uses this to calculate overall ignition
> timing based on the sync pulse. With the HEI it can just calculate
ignition
> timing per pulse etc. and let the HEI "worry" about which cylinder it is
> firing.
>     Anyone have more input on this or maybe something I have missed??

The sycn signal is only needed on SEFI.  The batch fire systems don't use a
sync signal.
Bruce
>
> Scott
>
> ASE certified Master
> With Advanced Engine certification.
>