Peak and hold injector drivers

[Garfield Willis]

On Wed, 24 Nov 1999 10:27:48 -0500 (EST) Andris
<askulte at emerald.tufts.edu> wrote:

>I'm upgrading from my 30 lb saturaturated SVO injectors to 75 lb/hr peak
>and hold injectors. The batch fire DFI is meant to use saturated
>injectors. Rather than spend $400 on the Accel VIC to drive the low
>impedence injectors, is there a (much) cheaper way to do this? I figured
>if an injector driver uses the saturated signal from the DFI as an input
>it could spit out the peak/hold signal. Timing issues aren't critical,
>since it is still a batch-fire system. Thanks for any help/insight :)

Those sound like pretty big whoppers, but the Cherry Semi CS-453
Injector Solenoid Drivers might still work for you. They are a
4Apeak/1Ahold devices, which I've used the smaller variety of (CS-452)
on some ordinary peakNhold mpfi injectors. They have alot of nice
attributes going for them (logic-level inputs, tho the inputs can swing
between supplies, load dump safe, wide supply range, heat sink tab is
ground), and yes you could easily drive their inputs from a previous ECM
output driver for sat injectors, except the polarity is wrong (they're
low = on), and would require an inversion (CS drivers are high = on);
that is easily done, tho.

After talking to Dr. Pelican about the Accel box, I was thinkin bout
making some of these as another product; but it appears the Accel box
also includes timing-per-injector to allow pulse stretching/narrowing.
The real question I have is just how necessary/desirable is THIS
particular pulse stretching/shrinking feature, or would there simply be
a place for 4/6/8 ganged "translators" from SAT to PnH? Admittedly, in
EITHER case, these gizmos are mostly a packaging issue, not much of a
circuit design problem, so it's not atoll clear it makes sense to
"productize" them. The thermal/vibe design of the packaging is probly
the most important thing, really.

I guess I'm really wondering just how safe/effective/useful/sane it is
to consider tweaking your fueling by an overall shrink/stretch of the
injector's pulse width? Sounds like an awfully global whack to the fuel
map; under what conditions is this hitting the nail on the head, or is
this a case of the proverbial "hitting a big nail, not quite on the
head"?

Gar