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aka mrubino83
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Discussion Starter #1 (Edited)
Starting a separate thread on this because my surge tank thread started going in this direction.

There was a lot of good input: Beeble, Clipse, Frankiago, Tephra, etc. So I would like to get it going in here again.

Basically the idea is to have the ECU control a secondary fuel pump, be a boost a pump, surge tank, etc.

The idea is to get a 12V signal to operate the fuel pump during high loads, and have it off at cruise/idle.

Based on the fuel pump circuit diagram:



Got it figured out: Heres how to do this:
Here is a picture with the relay removed, Im pointing to where the ECU wire (pin 51) connects to that relay.


See the blue wire coming through the opening above it? That is tapped into that pin from underneath the fuse box. The fuse box pulls apart and you can access the wiring inside.

Pin 51 is a Red and Black wire, thats the one you want to tap.

Remember: You will see 14v from this wire with the key on/engine off. During cranking this will drop to zero, then jump back to 14v at idle. This is the correct wire.

To change the output of this wire to power the pump I wired a SPST relay like this


Thats it! Connect to your pump and you have an ECU triggered fuel pump.
 

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Logic sounds right. I am sure they did it for some economy reason but I have been thinking of bypassing my WOT relay with a shunt and just run the pump at the higher voltage and then not worry about the relay wigging out. I have read somewhere someone was doing this with a surge setup and even when upgrading the fuel pump, basically just using the ~9V to drive a relay for the pump at the nominal 13.8V.
 

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aka mrubino83
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Discussion Starter #3
Logic sounds right. I am sure they did it for some economy reason but I have been thinking of bypassing my WOT relay with a shunt and just run the pump at the higher voltage and then not worry about the relay wigging out. I have read somewhere someone was doing this with a surge setup and even when upgrading the fuel pump, basically just using the ~9V to drive a relay for the pump at the nominal 13.8V.
Just to be clear, in this setup I am referring to, the variable voltage (9-14v) would still be in place and running the in-tank pump. The second relay utilizing pin 51 would act as the on/off switch for the 2nd pump.
 

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Just to be clear, in this setup I am referring to, the variable voltage (9-14v) would still be in place and running the in-tank pump. The second relay utilizing pin 51 would act as the on/off switch for the 2nd pump.
Correct...sorry I didn't explain in more detail.

I meant effectively shunting ~14V full time to the in-tank pump even with single pump setups, so essentially shorting out "Fuel Pump Relay 1". The other setups what they basically did was use the drive voltage feeding the in-tank pump itself through a relay in the trunk and then have that relay actuate via the ~9V-14V feed...so the pump see's ~14V all the time. :shades:

I was just talking about doing this the other day with my shop. I am going to take one of the old green or black relays and crack it open and solder the poles together to run the pump at a higher voltage. I will report back, I may just use it for when I am racing, not sure yet.
 

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aka mrubino83
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Discussion Starter #5
Correct...sorry I didn't explain in more detail.

I meant effectively shunting ~14V full time to the in-tank pump even with single pump setups, so essentially shorting out "Fuel Pump Relay 1". The other setups what they basically did was use the drive voltage feeding the in-tank pump itself through a relay in the trunk and then have that relay actuate via the ~9V-14V feed...so the pump see's ~14V all the time. :shades:

I was just talking about doing this the other day with my shop. I am going to take one of the old green or black relays and crack it open and solder the poles together to run the pump at a higher voltage. I will report back, I may just use it for when I am racing, not sure yet.
I see. There are a lot of people doing this, Same thing as "hotwiring" the pump. Essentially just bypassing the relay, just a few different ways of going about.

Seems like downsides would be increased noise from the pump, decreased pump life, possible heating of the fuel.

Although thats just thoery, in practice there are a number of people doing it without issue.
 

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In the middle of making this all work.

I have been going over revisions of this in my head sooo many times now
But what i think i will do is this :
1) use a two-pole relay (replacing the OEM fuel pump relay) - so this would switch the OEM pump into "full voltage" mode with one pole, and switch on my secondary surge tank pump with the other pole

OR

2) leave my upgraded pump in the OEM location (say a DW300/Wally400 etc) - and always have it running at low voltage. Still probably will have higher output than the OEM one at full noise. And use the OEM fuel pump relay or an aftermarket one to switch the secondary pump on INSTEAD of switching the OEM location pump to high voltage mode. Some ghetto wiring necessary for this option.

I'm just doing some math to make sure a DW300/Walbro400 on low volts will still fill the surge tank when I'm at WOT. I think it will as pressure is very low so flow will be high.


I've got my surge tank and twin Walbro 255s sitting here waiting, aswell as the lancer fuel pot from Canadia. So it's all ready to roll as soon as i finilize the electrics side of things.

** the catch with my plan of stock location Wally400 as the "lift pump" ; while at low voltage all the time, it will still have overrun issues. Adding a 255 into the mix may pressurize the whole system too much. Which is why I'm hoping to completely change the return system setup...

** other option is to get a proper "Low Pressure" lift pump in the stock location, and set it up as per option 2. Should minimize the overrun issue at idle/cruise
 

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aka mrubino83
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Discussion Starter #8
In the middle of making this all work.

I have been going over revisions of this in my head sooo many times now
But what i think i will do is this :
use a two-pole relay (replacing the OEM fuel pump relay) - so this would switch the OEM pump into "full voltage" mode with one pole, and switch on my secondary surge tank pump with the other pole

OR

leave my upgraded pump in the OEM location (say a DW300/Wally400 etc) - and always have it running at low voltage. Still probably will have higher output than the OEM one at full noise. And use the OEM fuel pump relay or an aftermarket one to switch the secondary pump on INSTEAD of switching the OEM location pump to high voltage mode. Some ghetto wiring necessary for this option.

I'm just doing some math to make sure a DW300 on low volts will still fill the surge tank when I'm at WOT.


I've got my surge tank and twin Walbro 255s sitting here waiting, aswell as the lancer fuel pot from Canadia. So it's all ready to roll as soon as i finilize the electrics side of things.
looking forward to seeing how this all goes down.
 

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I've got my surge tank and twin Walbro 255s sitting here waiting, aswell as the lancer fuel pot from Canadia. So it's all ready to roll as soon as i finilize the electrics side of things.
So you're trying the base Lancer pump hanger to see if that helps the back pressure issue?
 

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^^ working 6 days a week atm so the time component is sadly lacking.
Haven't even had time to test pins with a DMM.
Every spare moment has been consumed with other people's cars lately! Time to send some love to my own car i think.
 

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So you're trying the base Lancer pump hanger to see if that helps the back pressure issue?
Correct.
It uses the OUTflow line as the siphon, and thus i can McGyver up a free flowing return back into the top of the pot.
The only challenge is whether the siphon assembly itself once again proves too restrictive - ie it won't let enough fuel flow into the surge tank to keep it full.

So while back pressue should no longer be an issue, fuel starvation to the surge tank might be the undoing of this setup.
 

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I think I have a better solution - Everyone goes to a 3-port or an MBC for boost control, so that leaves the passive boost control solenoid circuit available to control the secondary pump. The one potential issue I see is that the BCS circuits are PWM signals, so I'd have to make sure that 100% duty does not cycle the voltage. I plan to hook up an oscilloscope to 3dman1's Evo tomorrow to check it out. I suppose worst case scenario is that I hack into the Passive WGDC control code to get rid of the PWM element. Other than that, I'll I'd need to do is write a small patch to use load instead of RPM in the Passive WGDC table. Fun fun.
 

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very awesome sir!
I've got mine working great the "old" way but this could be much easier for wiring it up ;)
 

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Load for a second pump would be very useful for myself...there seems to be a small spot in between 0psi and the 4-5psi where my car could use the pump but I don't want it to be at zero psi.

In for results!
 

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aka mrubino83
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Discussion Starter #17
Load for a second pump would be very useful for myself...there seems to be a small spot in between 0psi and the 4-5psi where my car could use the pump but I don't want it to be at zero psi.

In for results!
The way I have mine wired up up you can get it to kick on whenever you want. Just adjust the tables for the load value/when you want the pump to kick on.

Thanks Mr. Fred :)
 

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The way I have mine wired up up you can get it to kick on whenever you want. Just adjust the tables for the load value/when you want the pump to kick on.

Thanks Mr. Fred :)
Is your second pump tied to the low/high voltage switch for the main pump as well?
 

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Both my pumps are using the same high/low voltage Fuel Pump relay.
Right, so the relay actually triggers the main pump to go from high to low and also triggers the second relay to turn the second pump on I assume. I still haven't done this, too busy with logging/troubleshooting other stuff.
 
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