EFI questions...

[Dale Ulan]

>    1.   In a MAF based system, how is load on the motor figured?
>         Along with that, given a choice of standard sensors, what's
>         the simplest way to figure load?   (I assume MAP)

You can determine load nicely by dividing MAF by RPM. In fact, you
must do this to determine the injection pulse width.
> 
>    2.   Are there any example of fuel maps available for public 
>         inspection?   I'm interested in seeing how some people
>         have interpolated the values, and what values they're using.
>         Ideally, I'd like to find a V8 map...

Actually, if you are using a *fast* MAF sensor, which is not filtered
very much, and if you use some of the modern engine control system
theory, you first end up determining the engine mass air flow directly
in grams per second. You do this by sampling the MAF synchronous with
the crankshaft, but you must over-sample by at least 2 times. You
can vary the over-sampling rate if you want. I do it at 45/2 degree
increments up to about 3500 rpm. Above this, I use 45 degree.
After this, the calculations are easy to do from first principles.

The real trick is getting a real sensor curve for the MAF sensor.
You may want to ask Bosch for a full calibration curve for one of
their sensors. Choose one you like first, though.

Generally the sensors are so fast that transients are reproduced well.
So are cylinder filling events.

>    3.   TPS sensors -- what info do we derive from them.   For now,
>         about all I can think of is how hard we're accelerating.
>         I'm sort of thinking of it as a analog accelerator pump.
>         One of the software folks asked, "Why do we even need them?"

You use it if you are dealing with slow sensors that can't correctly
respond to transients. Also a problem with slow computers, etc. Basically
when the control system doesn't match the theoretical requirements.
Yes, you use an accelerator pump on it.

If you're a bit more adventurous, check out some of the articles in
the 1992 through 1994 engine control special publications (SAE).
There's one on a manifold pressure observer. This one looks like it
might be neat to implement.
>           
>         Are there different sensors for different engines, since
>         a V8 might have a different knock "signature" than a
>         I4?

Yes. They have different resonant frequencies. There are also
different amplifier modules for those systems with separate knock
amplifier modules.
> 
>    6.   A little off the FI subject; I noticed that the GM DIS system 
>         (At least on a '91 Cavalier) uses the same control wires as
>         the old C3 compu-distributor system.   Do they use the same 
>         form of control?    If so, what's the control method.

If it's a 4-wire system, probably yes. You have a ground, ref out
to computer, spark signal in from computer, and bypass from computer.

Bypass = low... spark occurs when ref pulse is on h-l transition.
ref pulse is fed to coil directly. The computer doesn't have to
do anything.

Bypass = high... spark occurs when spark signal line goes from low to
high. Coil is on when spark signal line is high.
Spark signal line has a pull-up in the distributor run off of the
bypass line.

-Dale