MC3484S2 Injector Driver

[Bill Lewis]

After giving up on the distributors, I called Motorola this week to try to
get a hold of the MC3484S2 injector driver chip.  They told me that the 2 amp
version has been discontinued - only the S4 version is still available.
Newark normally stocks the S4 version, but is currently on back order.

The National LM1949 seems just as hard to obtain and isn't nearly as nice to
work with since you need those pesky 0.1 ohm sense resistors and the
power darlington.

Both companies are sending samples.  Unfortunately of course, Motorola is
sending the 4 amp version.  Motorola was extremely friendly and generous
about the phone call, and National acted like I had pulled them away from
playing Solitaire.

Am I correct in assuming that the MC3483S4 is completely useless with the
2.4 ohm injectors?

What is the best (easiest) way to drive these injectors?  I'm mostly interested
in less board space and less heat to get rid of inside my controller box.

I've also been assuming that the old Bosch injectors that used to run in
series with a 6.5 ohm speed-up and current limit resistor are the same ones
used with these 'peak and hold' circuits.  I've based that on the coil
resistance of about 2.4 ohms.

I have also seem some Bosch injectors from a Chevy V8 that had a 16 ohm coil.
Are these intended to be driven by full battery voltage?  Did GM use this
approach to save money on the driver circuitry?

Someone in this group indicated that rather than looking for new injectors
to get more fuel, he would raise the fuel pressure.  Can that trick be
used successfully in reverse to get less fuel from a too-big injector?
Below some magic point, wouldn't that foul up the spray pattern?

.../Bill

-- 
Bill Lewis - wrl at access.digex.net