Injector timing qns.

[Craig Pugsley]

Dale Ulan writes:

[...]

> SAE Paper 810449, 'Mathematical Model of a Throttle
> Body Fuel Injection System' by Robert Esperti is a particularly
> good paper on this (although it gets mathematical). If you are
> into reading papers, 810494 and 810495 are pretty good, as well.
> Paper 790742, by G Czadzeck and R Reid of Ford, is a very good and
> readable paper on the Ford CFI 5.0L 1980 cars. It covers most of
> the 'twiddle factors' required to get the vehicle running properly.
> Also, paper 800164 on the GM TBI system is nice easy reading. Neither
> of these last two papers have any amount of hard math in them.

Thanks - at last!!! some _solid_ info about how the algorithms work (I'm
sick to death of the usual "and-the-rpm-combined-with-the-air-flow-meter
-and-temperature-makes-it-go-gee-wizz" stuff found in most books on the
subject.

While I'm here, two more questions for comment:

i/  What features does the HC11 have that makes it the 'processor of
    choice'? A-D, PWM, timers, watchdog, UART, high speed etc?
    Or is it more because it's an industry standard CPU?
    [I have limited experience with Z80 and 8051 processors].
    It would seem logical to me to use a microcontroller than just a
    processor (Because I couldn't be bothered designing extra hardware
    when it's not needed, and a microcontroller is cheaper anyway)

ii/ I want to make a 'gas analyser' with a Heated oxygen sensor.
    However, the idea is to make it so that the HEGO is in a bit of pipe
    /copper tube etc that can be put up the exhaust to 'sniff' the gas,
    and the reading displayed on a meter or just lean/stoic/rich LEDs.
    Obviously there will be the characteristic 'step' in the output
    voltage as it goes from lean to rich, but cost is the driving
    factor here. (IE no UEGO).

    The question is if a HEGO will work properly in this situation.
    i.e. all the heat required for operation is generated in the HEGO
    by it's resistor. Presumably I'll also need a fan or something to
    suck the gasses past the HEGO-will dilution be a problem?
    Any other forseeable problems?


Exhaust pipe
____________________________
  .  .    .  .. .   .   .  .. .  .      (.= Exhaust gas)
..      .      .   .     .     .  .
 .   .    .   .   . ___________________
  .   .      .    . ________________  | <--- Sampling pipe
____________________________        | |
                                    | |
                                    | |          _________ 
 (#=HEGO)                           | #----------| meter |
                                    | |          |       |
 (@=fan or other vacuum source      |@|          |_______|
    to suck gas past the HEGO)

Cheers,
Craig.