saturated vs. peak and hold injectors

[Tony Bryant]

> >> If you have hands on experience with times that low I will feel better
> >about
> >> what I'm doing. But what you are telling me does differ from every
source

Here's my experience if anyone is interested on driving peak and hold
injectors:

Injectors are 1982ish Nissan/JECS 240cc/min low impedence (greyish blue
case).
Fuel pressure = fixed 39psi above atmospheric

Peak and hold currents are about 2.2A and 0.6A. Voltage was about 12.3V
when I did my tests. I have a 39V back EMF clamp zener.

I tested them by feeding the LM1949 with a variable duty cycle signal at
around 50Hz. (i.e. 20ms period), and measuring the output in a burette.

I found 3 regions:

1) Linear above about 1ms: follows the equation:

            fuel =  (time-0.5ms) * rate

2) No flow below 0.5ms (no surpise really since 0.5ms is the opening time).

3) Roughly square law between 0.5ms and 1ms,

            i.e.
                if t=1.0 flow = n
                and t = 0.5 flow= 0
                then t=0.75 flow = n/sqrt(2)

Hope this enlightens someone. It sure explained alot of bizzare idle
symptoms to me.


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