Injector drive circuit mods?

[Mike R Brown]

John Andrianakis wrote:

> Dear all,
> I have a Weber ecu :W45.06/L20_67. It drives 4 2.5 Ohm injectors. I want to
> add another four injectors. I am aware of the special chips by Cherry and
> Motorolla that can drive peak and hold injectors correctly but I do not have
> the time to source them at this moment. The injectors are driven by BDX53M
> power darlingtons with some smaller transistors all controlled by some ICs I
> cant recognize.(This might be not correct, I just figured it out looking at
> the pcb.)
> I think I could possibly try  two options :
> 1)Install the secondary injectors(they are peak and hold too) in line with
> the primaries thus doubling the resistance and inductance seen by each
> output transitor. Probably would have to add inductive kickback
> protection.Could anyone guess how thta would change the range of the
> injectors?
> 2)Use another set of four same spec output transistors(BDX53M) to drive the
> injectors. Connecting the bases of the additional transistors in parallel
> with the ones in the ecu. I have no idea how that would effect the driving
> IC and or the current regulation.
>
> I am mechanical engineering student so my understanding of electronics is
> basic.
> I would appreciate it if someone could help me out correcting my thoughts or
> pointing out a different-better way.
> Thank you very much.
> John Andrianakis.
>

John,
    Have been doing a lot of work with my Edelbrock Pro-Flo.  It uses a Weber
IAW4W6 ECM.  The output stages in your unit sound a lot like the ones in mine.
Take a look at http://www.sonic.net/~mikebr/ecu_hdwr.html  I've got schematics
of my unit I've created.  Might help you in figuring out what you have in
yours.

Mike

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