[Diy_efi] Dual TBI ECM mods

[jlg-sep at comcast.net]

For an in-car ECM application like the '747, they'll hold up just
fine.  I'd be more worried if it were an underhood like the '727.
However, you could always upgrade the driver transistors like
the '749 guys do and use the Fairchild HUFA76429P3.  You'll
also need to increase the size of your injector fuse.

-Scott

-------------- Original message -------------- 

That sounds pretty simple.  I take it that the transistors (Q9 and Q10) can handle the additional current they are being asked to supply (double), would that be true?  Or would I need a different transistor that can handle the additional current.  Thanks for the help.

Dave


jlg-sep at comcast.net wrote:
> I am new to this and I suspect this subject has already been discussed,
> so I hope no one will mind me possibly bringing it up again...
> 
> My question is this:  I want to use a 1227747 ECM with 2 TBI units.  In
> other words, I need the ECM to work with 4 injectors instead of the normal
> 2.  Does anyone know what changes need to be made to the ECM to drive
> the additional injectors?

Reference the following schematic from Ludis' site:

http://www.cruzers.com/~ludis/1228746sheet5.gif

At an absolute minimum, you need to remove R79 and R80 (Left and Right
injector current sense resistors) and replace them with .05ohm 1% units.
I've been using the Ohmite 3W version, available from Digikey under p/n
13FR050-ND.  You will then be able to run the second TBI injectors in
parallel with the first while still retaining proper peak and hold operation.

-Scott
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From: David Rowley <david_rowley2003 at yahoo.com>
Subject: Re: [Diy_efi] Dual TBI ECM  mods
Date: Thu, 10 Nov 2005 15:38:51 +0000
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