Injector driver board- bosch and siemens injectors

[Seth]

Hello all-

First of all, I want to thank everyone out there for my help with this 
project ( the staged injection for a VW golf using a 68HC11F1) without 
your help, I would never have tried.  

I tested the injector driver board today. Using a National Semiconductor 
LM 1940 voltage regulator and LM1949 injector drivers.  I set the timer 
to 1.5 ms with a 15k resistor and a .1uf cap.  Tried 0.09, .18 and .47 ohm 
resistors for the sensing.  I tried this with chrysler injectors- two 
styles which are bosch and siemens.  Bosch are 280155703   12.3 ohm, like 
the siemens/deka which  is a 4612402.  The bosch goes in an early (pre- 
production) neon, I can't imagine they changed injectors, but who knows?  
The siemens deka comes from a 1995 or 1996 3.3liter  grand voyager SE 
van.  Canadian spec, I think. 

With the 0.47 ohm resistor, i got the 4:1 difference in injector current 
from peak to hold for both injectors.  I didn't with the 0.18 and 0.09 
ohm resistance.  The .18 ohm had about a 2:1 current difference.  The 
0.09 sense resistor wound up running the injectors saturated.  ( I think) 
In a discussion with my electronics prof. ( he was helping me)  he seemed 
to think that a notch in the initial voltage rise was the beginning of 
injector motion.  By varying the pulse width to the injector, we 
determined audibly that the injector didn't open if this point (typically 
1.08 to 1.2ms, and about 550 ma) wasn't crossed. We figured that the 
opening current for both the injectors was about 550 ma, the Bosch opened 
about 0.1 ms faster.  Perhaps the pintle is smaller with less inertia?  I 
don't know.

At this point without actually observing fluid out of the injectors, we 
canot be absolutely sure that the injectors are holding open after the 
initial opening surge.  By dialing the duty cycle up to 96-99% the 
injectors became quiet ( and the scope was showing some high voltages)  
below 13% duty cycle at 100.0 Hz ( ~1.3 ms pulse) they were quiet.  I can 
only assume that they were "holding".  

My question-  does anyone have a definitive bench test for injector that 
doesnt involve flowing fuel thru the injector?

Thanks, 

Seth Allen

(graduating soon (again) and looking for an automotive job)