your mail

Jonathan R. Lusky lusky at
Fri May 6 03:09:44 GMT 1994

> What voltage does an injector need to open?  If it is an electro-magnetic
> device like a solenoid then voltage isn't really important, as long as
> there is plenty of current.  If the voltage level is important, then it
> would be simpler to use a regulator to keep the voltage constant at, say,
> 10 volts.  If battery voltage drops below that, the car isn't going to run
> well anyway, regardless of what the injectors are doing.

The way "standard" peak and hold injectors are designed to be driven is
with an initial pulse of 4 amps to pop open the injector and a
continuous 1 amp to keep the injector open.  Since the injector
resistance is fairly constant (don't know what is off the top of my
head), you can calculate what voltage is required.  I'm not that
familiar with standard 4/1 peak & hold drivers, but I believe they will
cover the regulation for input voltages higher than required voltage to
the injector.  The voltage correction table is necessary for voltages
lower than that voltage.  Regulating at 10 volts is probably 1) too low
to get 4 amps to the injectors to open, and 2) higher than the voltage
some vehicles may see during cranking.

Heres the voltage correction table that came in our EFI Technologies

	V	microseconds to add to on time
	> 15.75	400
	14.63	432
	13.5	480
	12.38	608
	11.25	784
	10.13	992
	 9.00	1248
	 7.88	1568
	 6.75	2000
	 5.63	2576
	< 4.50	3296

I'm not sure why they began the table with 400 microseconds, that may
have been the estimated opening time for our injectors (GM Multec).
Also note that the EFI Technologies box doesn't just look up the values,
it also does interpolation.

Jonathan R. Lusky  --  lusky at
 "Turbos are nice but I'd rather be blown!"
   89 Jeep Wrangler - 258 / pile of junk!
       80 Toyota Celica - 20R / 5spd

More information about the Diy_efi mailing list