Per my tuner's recommendation, I'm going to hardwire my Walbro 450 fuel pump. After doing some research, I'm going to use the following diagram. From my understanding, this will bypass the FPC on the power side, but still use the ground signal to the FPC to control FP duty (33%, 66%, or 100%). In speaking with Brian at iWire, he's questioning the benefit to wiring it this way at all since the power is still going back through the ground and routing to FPC and the FPC is still a "bottleneck"... From Brian: "So I get the theory because the power side gets some voltage drop through the module, but I think there is a flaw in practice because of the way electricity works (keep in mind I'm not an Electrical Engineer). DC flows like water from the power feed (battery) to the ground end point (battery negative or a something metal). So if it needs a good flowing path to ground, and that ground goes through the module too, then wouldn't it have the same problem as the power side? Possibly even worse because the ground side is the part that regulates how hard the pump is working, so there is more circuitry that is involved thus more places for electricity to be dammed up or lost to other outlets. Seems to me, the only way to really make a difference (which I'm not convinced for most setups is necessary) would be to run the ground direct to chassis using a short, proper gauge wire and run power direct (via a relay) to the pump itself. That way you have a free flow from start to finish and still have the ability to turn the pump on and off with the ECU." Is there a better way to accomplish this? What he's saying makes sense, but I'm not sure that I'd want the pump running 100% at ALL TIMES (with the key on), which is what would happen if bypassing the FPC entirely and running it off a relay. Any input/experience on the subject?
So if im reading this right you are concerned that if it is wired the stock way you will not get the full potential out of the fuel pump is this correct?
I guess in my mind then you have the wrong fuel pump if you feel like you wont get enough fuel while running it as intended. I ran mine with stock wiring and 1200cc injectors and it worked fine. Maybe you have a thread started somewhere that explains more of your build and why your looking to need to do this but if you could summarize for us in this thread that would help us out.
I think the 450 is one of the largest in tank pumps you can get without getting into running dual pumps/custom hangers, surge tanks, etc. ID1300's Dom 3.0XTR All supporting mods ( https://mnsubaru.com/threads/07-98-rsti-build-thread-lola.51875/ ) This is per the recommendation of my tuner, so I trust that it's a necessity to get everything out of the pump. I'm just wondering the best way to accomplish it from a wiring standpoint.
I emailed him asking for his input as well, but haven't heard back. Figured I'd see what y'all thought in the meantime
That "diagram" makes my brain hurt.....a LOT. Whoever made that either thinks they're hilarious, or has no fawking clue how the circuit (or DC electricity in general) actually works. My money is on the latter. I'm downloading the '07 Impreza FSM now. I ASSume the wiring/ECU/controller are from that, right? IMO, you either leave it hooked up as intended, or you bypass the controller entirely. Adding a relay (if you do, the fuse goes BEFORE the relay, jesus) is just adding complexity for no reason. If the controller really is adding resistance to the ground side, it's still effectively reducing the voltage across the pump....I see no advantage.
LOL I noticed the fuse being in the wrong spot as well. I have the 07 FSM, I'll see if I can find the FPC wiring. I didn't make the diagram, it was just the easiest one to read that I could find haha And your last paragraph is what Brian was saying too, which made me question the whole "hardwiring" thing entirely.
I debated this as well during my build. You can go aftermarket FPC, they are not that expensive in the grand scheme of things (if you truly care that much about the pump running 100%). At the end of the day, I opted to hard wire my fuel pump (no FPC) and, the car and pump are running fine (3 yrs). I also had the same 450 pump.
FSM finished downloading and I've had a minute to look. It doesn't have a detailed function description for the controller. Just that it controls both the power and ground side of the circuit from the ECU to the pump.... If your tuner is recommending bypassing it, just bypass it. You can just simply bypass the controller (take the power wire pictured coming from the key there, and go straight to the pump, and pump ground straight to the Engine ground wire going to the controller). Downside of that, is the fuel pump relay is always on if the key is, which is not ideal. That may be the purpose to adding that relay, but if the power supply coming off the controller is limiting voltage, it might drop below the switching threshold of the relay, and the pump would shut off.... I would love to hook a multimeter to the controller on a stock car and see what it's doing.
Yeah, I know DCCDPro makes a FuelPro controller and there are others out there as well. I just don't think my build is extravagant enough to warrant having a fancy FPC. I wouldn't be too worried about the FP running 100% all the time if this was strictly a track car, but it will see plenty of street time. I would think running the pump that hard during idle/low load situations is just heating fuel and that's about it. Maybe that's not even that big of a deal, idunno. Thanks for taking a look. I couldn't find anything except for how the wiring is routed, nothing specific about what pin does what. I know there are folks who hardwire their pumps as depicted in my half-ass "diagram" and some have posted lower IDCs readings after making the modification...moderate improvement, but improvement nonetheless. I think I'll see what the tuner recommends and go from there.
Still haven't heard back from my tuner on the subject, but I did some more research today and determined that running the ground back through the stock FPC is out of the question. The main reason for hard wiring the pump is to bypass the stock FPC because it cant handle the higher amperage draw required for a larger fuel pump, so sending the signal/ground wire back through the stock FPC defeats the purpose... So an aftermarket FPC like the FuelPro or Aeromotive FPC are looking like viable options. The FuelPro unit is cheaper and more than sufficient so that's probably what I'd go for, but it's still $200... Other option is to straight hardwire the pump (10 awg from battery (fused) to relay, 10 awg from relay to pump+, 10 awg from pump- to chassis ground, stock power wire that used to go to the pump from the FPC now goes to the relay to trigger it on when the ignition is switched to ACC.) My concern here is shortened fuel pump life as well as heating fuel and/or cavitation in the tank from running the pump at 100% at all times. Anybody running a FuelPro controller? I have a feeling that's the route I'll be going, although I'm not excited about dropping 200 bucks on one.
Well after much debate and nearly pulling the trigger on ordering a FuelPro, I just directly hardwired it. I couldn't find too many people using one and the general consensus was that hardwiring it direct would be fine; many have done it with no issues for years. Hopefully I don't run into any issues.
I guess they supposedly have a 10k hour life expectancy, so hopefully won't be for a long time. And to clarify, I didn't wire the pump like I had originally posted. 10ga fused wire from batt to relay 10ga wire from relay to pump (pre molex connector) 10ga chassis ground to pump (pre molex connector) 16ga chassis ground to relay 14ga switched 12v (originally going to FPC) now triggers the relay Pump runs 100% with key switched to ON
Been running 100% on fuel pumps in the race buggys for years. Only problem was fuel pickup on a low fuel cell in off camber situations, the pump is cooled by the fuel running thru it. Walboro fuel pickups in each corner( if it sucks air the individual pickup closes) plumbed together solved the problem.
