RE: Considering Injector Change..

["the Fredericks" <fredericksk@worldnet.att.net>]

Mike,

If you're using the Cherry P&H drivers, it actually ends up looking kinda
ugly when you put them on an ECM motherboard in place of the original
transistor drivers.  I'll outline what I do; maybe it'll help you decide
whether you want to tackle it or not.

For detailed application notes and a pinout on the P&H drivers, look at
Cherry's web site; they have the PDF application notes for them there for
download.

The driver is a 5 pin TO220 case package; input, output, bias, ground, and
"trip" pins.  I bend the input, output, and ground pins to allow them to fit
into the corresponding holes in the motherboard.

I remove the original drivers by desoldering them and removing them from
their heat sink.

The P&H drivers have one pin that can be attached to a voltage divider to
allow the driver to trip to "hold" current if the supply voltage drops very
low; I clip this pin and solder it to the ground pin.  You could implement
this feature, but I haven't found it to be necessary in a decently supplied
ECM.

I then bend the pin that attaches to the bias resistor up and insert the
remaining 3 pins of the driver into the m/b and solder.

I use a piece of perf board sandwiched in the ECM case and mount the flyback
protection zener diodes and bias resistors on it (see application notes for
recommended values).

I then run a wire from the anodes of the zeners to ground and solder each
zener to its' corresponding driver's output.

The last step is running a power wire from a good source on the ECM m/b to
the bias resistors, and soldering a wire from each of them to its driver's
bias input.

I have seen other people do them without a board, omitting the zeners and
gooping the bias resistors and wiring flat across the motherboard with
potting compound.  I think the zeners are a good safety addition, and this
looked like more of a PITA to me than just mounting them on a small board.
You could also put the entire thing into a separate box outside the ECM and
wire it externally; that might be the neatest method.

Anyway, that's about it; hope it helps!
Kendall Frederick

> -----Original Message-----
> From: owner-gmecm@diy-efi.org [mailto:owner-gmecm@diy-efi.org]On Behalf
> Of ECMnut@aol.com
> Sent: Tuesday, July 25, 2000 9:15 AM
> To: gmecm@diy-efi.org
> Subject: Re: Considering Injector Change..
>
>
> Kendall,
>  I wanted to try a driver upgrade on a spare ECM for my friend's GN, but
> I'm a chicken with a soldiering iron.  Would you mind giving
> some simple instructions?   This is a popular mod these days.
> Maybe we could make a "how to" page.  Or does it already exist?
> Thanks,
> Mike V
>
> >  I'm running the 7148 (stock GN) ECM, with P&H Cherry
> Semiconductor drivers
> >  installed by yours truly.  The 55 lb/hr injectors are low
> impedance.  The
> >  guy w/the 72s is running the Accel DFI batch fire system; I
> don't know what
> >  sort of drivers are in it; never had occasion to take it apart.


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