has anyone doen this? i just had a thot last night about this...

 

It has been covered. You may find it with a search or two. I cannot remember any of the details off hand.

 

It's been a while since I have seen any of those posts but I think there was a problem with getting four injectors to fire with one ECM.

 

couldnt you just splice them with the other 2 wires for injectors
and have them crossfire? like this

(X) ( )

( ) (X)

 

The problem is the drivers in the ECM will fry. I have thought of using power transistors to reduce the load on the drivers but doubt it would work very good.

 

You could wire the second pair of injectors this way. But, you won't get consistent behavior. The answer is a separate driver circuit for the 2nd pair of injectors. If you search for posts relative to the Holley 4 injector TBI unit, you'll find a few people who have tried this.

Two other things you'll probably have to do after the injector stuff is worked out would be to fabricate throttle linkage between the TBs and plug one of the IACs......?

 

I don't think anyone has had major sucsess with runing dual TBI, or holley 4 barrel (with GM ECM). If you want the power and airflow for a done motor, go to a big carb with spark still run by the ECM. From what I know it'll probaly run better than dual TBI. Even if you got the injectors working perfect, theres still IAC problems, fuel mixing problems, linkage problems, etc..

 

All you have to do is wire the IAC in parallel like GM did on the Crossfire.

 

GM sells (or used to sell) a dual 2-bore TBI controlled by MEFI 3 for their supercharged marine big block engines. I know because I posted the info on it. Do a search with keyword MEFI and you'll find the thread(s).

There are other ways to get it done, incl some schematics (posted here on TGO) for driving the second pair of injectors, and a lot of it has been previously discussed on one of the DIY-EFI web mail digests. The TGO thread will be easier to find, but the digest-based DIY-EFI discussions won't be as easy to find because the search tools, AFAIK, aren't as good.