I'm new to the forum but I've been reading for months collecting info for for my current project. It's a dual gm tbi setup on a chrysler 413BB. I have all the parts collected and the unnecessary junk stripped from the factory harness, I'm waiting on my tuning hardware from maotes and the only question I can't find is how exqctly do I modify the 1227747 ecu inj.drivers to run four injectors? I think i need to remove the factory .1 ohm resistors(2) with .05ohm resistors??? Anyone that can shed some light would be great. And I'm sure I'll need some tutoring on tunerpro aswell,lol. Thanks in advance.

 

The 747 was not used on f-body's . This sounds like a question for a truck forum.
You do not state the ohm injectors you are trying to use ? Taking that into consideration
Have you thought about the 1227730 or 749 ? .

 

On other TBI ECMs, I don't modify the injector drivers, I just run pairs of injectors in series. It's working well on a pair of my friend's 4 BBL injected Olds engines.

The 4 bbl TBIs were made from GM throttle bodies. He's using '7060 ECMs, but they are just a newer TBI ECM than you will be using.

 

Hmm, ok. I saw that robertf did the dual tbi setup with the 7747 and said he had to mod the driver resistors. Im not sure the ohm rating of the injectors, they're factory 4.3 inj. Tho. I haven't rly looked into upgrading to a newer ecu, I was just kindof running with what I had to keep it a bit more simple.

 

Oh ya. Robertf said when he did his build that the circuit had to have the .05ohm resistors because the ecu wouldn't allow enough current to fire 4 injectors with the factory .01ohm resistors. Another thing I was contemplating, what watt resistor do you guys think I should use if I do happen to need to solder in new ones? Surely 2 or 3 watts would be enough?? Idk how much current is run through the inj. circuit.

 

http://www.chevyforums.com/fusionbb/...hp?tid/104584/

 

So what I take from that is, yes I can reduce the circuit resistance by half, up the heatsink and may have to upgrade the transistor and it will work. Maybe i can install a small muffin fan to keep the pcm cool. I also had an idea, does anyone think I could run 2 throttlebodies with one large injector in each one with a RRFPR to supply enough fuel at higher rpm.

 

Bump. Anyone wanna add anything?

 

If you read that linked thread, he says you need to do a trace fix on the board. It sounds like the traces burn up on the board due to the higher current demand. Just an extra bit I took from that thread.

 

http://www.dynamicefi.com/InjectorDriving.php

 

Ok, I just got some mind blowing info! Ive heard all about the resistor swap mod for the injector drivers but I just read thqt the 7747 comes from the factory with four separate drivers and only the 350 and 454 have the injectors wired to them. Ill post the link take a look and tell me what u guys think. If it's for real I can just wire each of my four injectors to each driver. Does anyone have a good pinout of the ecu internals?
ftp://ftp.diy-efi.org/pub/gmecm/manu...47/747ecm6.jpg