Injector supply voltage & positioning.

[Steve=Ravet%Prj=Eng%PCPD=Hou at bangate.compaq.com]

faustini at lamp0.arl.army.mil (Lou Faustini) Wrote:

|     Aren't injectors a binary-type thing? ... Either they are on, or they 
| are off right?. I thought there was some mechanical hysteresys built in.
| I assume if you were to drive them at very low voltages you might find a 
| point where they are in a semi-open state, but I assume that that voltage
| would probly be around 5 or less volts. I know that Toyota corp actually
| puts a 2-ohm resistor in serise with their injectors. They are also 
| low-side swithced. 

They are, except for turn on and turn-off time.  At high and low duty cycles 
the turn on and turn off times can be significant.  A higher voltage will open 
the injector faster.  The two ohm resistor is for current limiting.  The 
impedance of the injector coil drops exponentially while it is on, ie the 
instant you apply voltage, the impedance is near infinite (or at least real 
high).  It drops quickly to whatever the resistance of the coil wire is, which 
is usually not much.  The coil will draw too much current by itself if left on 
for too long, hence the resistor to limit current.  A better solution would be 
a transistorized constant current driver.

| 
|     Question.. What fuel pressure do you folks recomend running the
| injectors at. I heard that the Ford-type injectors, like the ones used
| on the Mustang V-8, run at about 40+psi. Is this true? That sounds like 
| a real problem for the hobyst who would like to use Trak-Auto fuel line.
| I know that my Holley setup runs 15psi. That is a little more reasonable
| to work/play with.
|                                ------ Lou Faustini

--steve