GM ECM injector driver capacity

[Jennifer and Brock Fraser]

> I think the injectors may rely on the fuel flow for cooling. It would
probably
>not hurt to run a short test dry, but I would worry about a long test with
dry
>injectors. you may be able to just put the injectors in a non-flamable, low
>conduction liquid to allow longer tests. If you know which device is the
driver
>in the ECM, it would be a good idea to monitor it's temperature rise with 8
>injectors, and then with 16. If the driver can handle 16 at reasonable
>temperatures, you could mount a larger heat sink or small fan on it to get
>through the higher ambient temperatures found in the car.

They pulse EUI's (electronic unit injectors - Diesel) at work all day long
with no cooling fluid on the test bench...  They might be more durable,
though.  As far as rumours go though, I've also heard that automotive
injectors need fuel for cooling.  Actually, thinking back to my CNG
experiences reminds me that it has a lot to do with lubrication, not just
cooling.  CNG is dry, of course, so light oil is added to keep the injectors
alive, at least when breaking them in.

Bruce, while you are tap dancing, maybe you could hold your thumb on the
drivers to see if they are getting hot.  Of course, like Ken says, running 8
injectors first would be a good baseline.  To reference your wiring
question, I'll send you a plug-n-play solution that all you have to do is
hook one end to the drivers, and the other end to +12v.  As you mentioned,
I'll have to get some of those little contacts to use on the injector
terminals.

> The idea of putting injectors in series will reduce the load on the ECM,
>however you have to make sure that the injector will work in this mode.
Since
>you only have 12 volts to pulse the injectors, if you put two in series
each
>will only see 6 volts. Don't know if they will respond quick enough at that
>level. On a cold morning when you are cranking you can easily drop down to
9
>volts accross the battery. This would be less than 4.5 volts on each
injector.

This is also a good point.  It sounds to me like the best idea is to wire
all 16 in parallel with each other such that they all get full battery
voltage.  After all, considerable software variables exist for the sole
purpose of correcting injector driver output values in accordance with
fluctuating battery voltage...  This alone indicates that the turn-on and
turn-off times of the solenoid ARE INDEED noticably sensitive to the voltage
applied.  Halving that voltage (as in the example above) sounds like a
pretty radical departure from the intended voltage range that the injector
is supposed to see for reliable and repeatable operation - especially at low
flow (short PW) situations like idling.  Keep in mind that the 16 injectors
are already going to have to be commanded for half of their counterpart "8
batch's" opening times.... hence creating idle stability problems similar to
BIG injectors like 50lb/hr units.

Nobody has quizzed as to WHY this plan is desirable, but I'm assuming that's
because it's obvious.  50lb/hr injectors (for example) ARE TOO DAMN
EXPENSIVE, even a jobber or WD pricing.

Thanks for the input.

-Brock