Injector Driver Module

[Mike Morrin]

At 11:17 AM 8/10/98 -0700, Jose  Rodriguez wrote:
>  There are mainly two types of injector coils: the saturated and the
peak-and-hold ones.
>  The saturated coils typically have 16 ohms resistance and yes, if I used
them the power dissipation would be greatly reduced on the injector driver
side, specially since I could saturate my drivers, so the power would be
negligible.
>
>  If most OEM coils are saturated, that would explain why they can do it
with such small heatsinks. I wish I could put the module in the interior,
but that is not an option.
>
>  Unfortunately, I am currently being forced to use the peak and hold
coils (1.5..2.3 ohms), because the injectors are to deliver a very high
mass flow, and work over -40..125C. I am told the saturated coils can not
reliably work under those conditions.

I thought I saw somewhere a circuit which generated the hold current by PWM
of the injector current, so the drivers were always saturated or off.  I
cannot remeber where I saw it, or whether it just used the internal
iductance of the injector, or an extra external inductor.

regards,

Mike