[darbikrash]

There are many different ways to wire, plumb, and tune EFI systems. I’ve tried several approaches, and had some failures as well as some success.

One of the EFI cars, the ’69 GTO has a Terminator system which is a throttle body EFI with remote ECU. This worked out pretty well, but as mentioned has a great deal more wiring harness than the throttle body mounted ECU’s. Because it is more or less a generic unit, the harness is way too long for most cars and you have to somehow hide or deal with this extra length.

Also not wanting to drill big holes in my firewall, after several tries I opted to mount the ECU behind the headlight on the passenger side, and route the harness behind the wheel well so its not visible. Another tip is buy a battery that has both top and side terminals, such as the Odyssey 1500, which gives you dedicated terminals (I use the side terminals) for the ECU without sharing the connection with any other loads.

For fuel lines, I mounted my regulator back by the tank and importantly, bought an extra 0-5v Holley pressure sensor to mount right at the throttle body. I have another EFI car with a firewall mounted return regulator, and a full car length return line also with a fuel rail pressure sensor.

I data mapped both systems and I see no difference in pressure drop from the tank mounted short return line system versus the firewall mounted fuel length system.

While the full length return line system with engine compartment regulator is no doubt “better” in theory, I can’t say that the car runs any better and the tank located system is easier to install. Just make sure you have a TB mounted pressure sensor to tell you exactly what the line pressure is, you can enter this value in the tune and get accurate injector performance- as long as the pressure drop is managed.

I’m not saying this is better than a conventional firewall mounted return regulator, but installed properly it does work just fine.