Maybe a « stupid » question, but with MrFred solution from post 121, I understand « low voltage » is coming from factory and then « high » is triggered with the Hobbs switch (for example 7psi like the one sold by Spoolin up).
I was intending to set the crossover table to something in load that matches with the 7 psi from the Hobbs switch, does it makes sense ?
I’m running EU SP98 gas pump only on 2.3 stroker and not a « monster setup », so 340 lph is Enough for me but I want to keep the benefit exposed in this thread.

 

Don't need to do that. Especially with the small pump.

 

thanks a lot for your input.
sorry, just to be sure since I’m not english native speaker 😀 : you mean I don’t need to try matching more or less the Hobbs setting with the rom table or are you talking about the whole rewire intention ?
I was thinking even my »small » pump would benefit from the rewire ( targeting around 500 whp)

 

It will benefit from the rewire, but the extra amps aren't needed until fuel pressure is higher. So it'll be fine with the stock crossover setting, and then the hobbs switch coming on at 7psi. The fuel demand, and demand on the pump due to fuel pressure is pretty low at 0-7 psi anyways.

 

Does this setup still work do you have issues with the pump staying on when the car is off? do you have an improved version of this?
What SSR did you use for this setup?
trying to retain the factory setup, just making it beefier to handle a larger pump.

 

It should be the same for ANY car that sends a lo/hi voltage to the stock pump, so although I have not tested on an Evo before the X, there is no reason it wouldn't work:

THE_LINK

 

Sorry to bring this thread up, but I have the issues that everyone said a while back in the thread. Adjustable FPR is being over ran by the hardwire kit. Would upgrading lines potentially fix that issue where the fuel is overrunning the FPR?

 

You need to go to a dual voltage setup, or perhaps upgrade the RETURN line and any limits in that return to the tank. The problem with this is your still throwing massive heat into the fuel by running the pump full blast even when your sitting at a light. I only have an Evo X, so someone would have to chime in if the previous evo's used the same hi/low voltage power to the OEM fuel pump. If so then checkout the link I posted above for a DIY solution.

 

I've been thinking about this, since most people just end up splicing into the factory wiring before it terminates into the fuel hanger connector, why can we just make the connection to the relay in the wire that comes off the factory fuel pump relay in the engine bay? saves running wires all the way to the back seat, instead you just have about half a meter of wire to the wiring coming off the factory relay before it goes into the cabin.

Or, is part of the reason for the rewire due to the voltage drop due to the gauge/distance of the OEM wiring?

 

from my understanding the reason for the rewire is to prevent the voltage/amperage drop due to the factory wires being too small

 

FYI, I have been running the same hot wired 485's since September of 2015 with no issues and the car is a daily driver. One 485 is hot wired full time and the second 485 is hot wired and activated by a Hobbs switch at 12psi.

 

I did this rewire over the weekend using the STM kit so I wanted some feedback to make sure I did the rewire the "proper" way. I also noticed some discrepancies with some of the install instructions and diagrams here compared to the STM relay I have, like connecting hobbs NO to 85 instead of 86 and vice versa. For example, the relay terminal 86 was the white wire and terminal 85 was the black wire so they are reversed compared to all the diagrams here. Most diagrams posted here show 85 to chassis ground and 86 to hobbs switch NO terminal. I ended up ignoring the wire color differences and just paid attention to the terminal # but maybe I did something wrong.

This is what I did:
1. Wire from add-a-fuse in fuse box 12v source to hobbs COMM terminal
2. Wire from hobbs NO terminal to 86 terminal on relay (white wire for me)
3. Terminal 85 on relay (black wire for me) to chassis ground
4. Terminal 30 on relay (blue) to battery
5. Terminal 87 on relay (yellow) spliced to power at pump (white wire)
6. Upgraded chassis ground wire spliced to pump ground (thicker black wire)

Is this correct?

 

85 and 86 is just the power coil on the relay. It doesnt really matter with one is grounded or power.

May a quick glance everything else sounds fine assuming you added this kit to a second pump?

 

Actually, some relays come with a flyback diode on the coil, and it does matter greatly which way these are wired.

 

One pump in the oem housing