Could a stock 7747 ecm run 4 tbi injectors without the aid of a piggyback ecm or aftermarket efi unit like megasquirt or an ebl board? couldn't you just hook up the injectors in parellel with the other 2 then tune the ecm for the new bpw of the 4 injectors or is the injector driver not strong enough to handle the additional injectors? Cause looking at the edelbrock tbi to mpfi kit looks like they're hooking up 8 injectors with just a chip change in a batchfire mode. I don't have alot of cash at the moment but i do have alot od spare and extra parts laying around so i'm trying to find different options to efi my 402 bbc?

You can drive 4 TBI injectors without the EBL setup. There is a 4-injector upgrade available separately. With this two injectors are wired in parallel on each driver.

The old way of doing it was to wire two injectors in series on each driver. But this severely limits the RPM range and control of the injectors because they open so slowly.

Wiring two in parallel on each driver doesn't work as they peak off too soon. Most of the time they won't even open.

The Edelbrock MPFI set up works because they are saturated injectors. There isn't enough current drawn to peak off the drivers. The drawback is that the injector firing rate for MPFI is half what it ends up being. So the system becomes RPM limited due to duty cycle limits.

RBob.

Can you purchase the 4 injector upgrade and install it ourself if so does anyone know how difficult it is to install? I have a friend that builds prototype boards and offered to do any electronics modifications i may need for my build.