Hello all, I am using the EMU black with PnP adapter on a 1990 Toyota Supra 7mgte with mostly stock wiring harness, other than added sensors coming back to the EMU.
In the EWD for this car and engine the FP output from the stock ECU goes to a fuel pump control relay that switches between running the fuel pump on full 12v and running it through a resistor to decrease voltage and run the pump slower at idle conditions. The EMU black PnP adapter and base map are set up so G6 INJ#4 is directed to the fuel pump control relay so when the fuel pump output is enabled by the ECU it switches the fuel pump control relay to supply voltage through the resistor, so the car currently is always running with the fuel pump not at full speed. My circuit opening relay is effectively my fuel pump relay in this setup, and it is controlled by G21 AUX#1.
I am running into low fuel pressure problems that I have been compensating for in the tune but I would rather solve my fuel pressure issues than keep cranking up my VE table. I am at 70+% injector duty cycles at 15 psi boost on 750cc injectors. My fuel pressure under boost is 25psi, at 15 psi boost so my fuel pressure delta is ~10 psi instead of the stock ~40-43, with the fuel pressure regulator referencing my manifold pressure. I suspect this is because of the fuel pump not running at full speed and supplying enough fuel. I will look into upgrading my fuel pump if I continue to have problems after this wiring/tune fix.
I could disable the G6 output in the tune, which would leave the fuel pump control relay in its normally closed, full 12v state, and the fuel pump would run full speed always, which I have no problem with. I could also delete the resistor from the harness, so the state of the fuel pump control relay does not change what voltage the pump receives. I believe either would accomplish the same goal but I would rather change a setting in the tune than remove parts of the stock wiring harness unnecessarily incase I want the functionality back at a point in the future.
I am wondering if there is a reason I missed for why the tune is set up this way, and I am missing that it would cause another issue if I were to disable it. From what I can tell it should be a simple one tick box to not have this problem anymore but that makes me think there is a reason Ecumaster set the base tune up the way they did. Any insight into the thought process would be appreciated if anyone has something to add.
Thanks for reading, sorry it is such a long post.