7749 ECU PW musings.....

[Roseanna Tisdale]

Been doing some more scoping, and have some observations and questions -

While running the benchtop ECU and reading injectors on the scope, I
noticed that the injector 'buzzing' sound stops *before* the electrical
pulses to them go flat-line (100% duty cycle).  This happens @ around 80%
duty cycle; now, granted, this is running in air, w/o any fluid or pressure
in the injectors.  But, I would assume that the viscosity of fuel in the
injectors, as well as the pressure of the fuel, would tend to *enhance*
this, not degrade it.  So, 100% *electrical* and *mechanical* duty cycles
appear to be different things.

Furthermore, per ALDL data stream info, they "max out" (go static = stop
buzzing) at an indicated 'on time' of 10ms @ 3000 RPMs, where there's
20msec available 'on' time.	 This I do not understand.  The *major* factor
in determining PW is manifold pressure, as you'd assume; cranking this pot
really changes PW.  The other factors (temp, TPS, etc) provide a 'trim'
depending on engine operating parameters.

In the data stream, there's also two bytes that supposedly give "Time
between reference pulses" (bytes 11 & 12 = OLDRFPER, OLDRFPER+1, MSB, LSB).
 This value *increases* linearly w/ RPMs, not inversely as you'd (I, at
least) expect.  If injector events happen on reference pulses, its
bassackwards.

Can anybody help out here?  I'm going to be trying to burn a good 40# chip
for my modded Sy, and I'd like a little more correlation between
"empirical" stuff, what actually works, and theory. 

My scope indication of "on" time of the injectors and what's reported by
the data stream are radically different, also.  Wrong both absolutely &
linearity wise.  I don't know what's up here.

Thanks for any feedback - Barry
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