Hopeful 101 background notes

[Gregory A. Parmer]

I've read pieces of this time and again but
it never seems to sink in. I'm trying to
collect the stuff idjuts like me should know
*before* we get hair-brained ideas. Please correct
where necessary for possible entry into the 
"101" project.

BTW--This is about GM systems

I.	First the DIS or C3I (distributor-less) ignition systems
    1)  AKA "wasted spark" system since 2 plugs are fired at once --
        one of them on the compression stroke and one on the exhaust
        stroke)
    2)  Plugs are connected in series. According to Chilton, "the cylinder
        on the exhaust stroke requires very little of the available
        voltage to arc, so the remaining high voltage is used by the
        cylinder in firing position (TDC compression)."
    3)  The firing of individual coils is not controlled directly by the
        ECM. The C3I module acts exactly like a distributor from the 
        standpoint of the ECM. The C3I module monitors the crankshaft and
        camshaft sensors and communicates with the ECM primarily by the
        EST signal just like its distributor cousin. The EST (Electronic 
        Spark Timing) signal controls timing advance/retard but does not
        control which cylinder gets a spark. That's all done within the
        C3I module.

II.  Now for EFI issues
   1)  Tuned Port Injection (TPI) and Multi-Port Injection (MPI) use
       batch firing of fuel injectors. Even though each intake manifold
       runner has an injector, the injectors for each cylinder bank
       (1,3,5,7 & 2,4,6,8) are fired together. This is opposed to
       Sequential Fuel Injection (SFI) which opens injectors in
       sequence.
   2)  Injectors are fired at a rate based on crankshaft revolution,
       as signaled by the crankshaft sensor or distributor.
   3)  Fuel pressure is around 10psi for TBI systems and may range from
       28-50psi for port injection systems.
   4)  Some systems used a fixed fuel pressure while others referenced
       fuel pressure from manifold vacuum.


-greg       Are there flamesuits and CSHats that match?