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Discussion Starter · #1 ·
Hey, have any of you heard this? And more importantly have any of you done this?
We suggest wiring a separate relay to the fuel pump so that it receives full alternator voltage at all times. The factory fuel pump circuit contains a resistor used for controlling the voltage to the fuel pump for low and high speeds. Even at the high speed setting, the resistor prevents the fuel pump from receiving full alternator voltage and ultimately limits the fuel pump’s flow capacity.
 

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I've got the Walbro but haven't done this mod. It seems a bit counter productive as it defeats the purpose of the regulator.

misterx
 

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AaronC said:
Ok, I found this poking around on the whateveritscalled club.

http://forums.nasioc.com/forums/sho...rpage=30&highlight=resistor pump&pagenumber=2

I wonder what would happen if you were to hard wire the stock FP. Would It damage it?
Pace had his fuel pump hardwired when he had his Link in his car. It was constantly on whenever the ignition was on. I don't think he ever ran into any trouble.

On a side note, does the WRX fuel system have a return line? That would be one of the issues to deal with if you plan on running the fuel pump on high all the time. The extra fuel needs somewhere to go.
 

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Discussion Starter · #7 ·
djrez4 said:
Pace had his fuel pump hardwired when he had his Link in his car. It was constantly on whenever the ignition was on. I don't think he ever ran into any trouble.

On a side note, does the WRX fuel system have a return line? That would be one of the issues to deal with if you plan on running the fuel pump on high all the time. The extra fuel needs somewhere to go.
It does have a fuel return line, but I dont know what kind of load the stock fuel pump can maintain.

Theoretically would the engine get messed up if the fuel pump fried? I would think that it would just cut off. Any thoughts?
 

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more stuff on fuel pump

First of all, the quote about a resistor is wrong. Who ever wrote that does not understand how the WRX manages the fuel pump, so keep that in mind as you consider using their advice. There is no resistor but the concept of cutting supply voltage is correct.

The WRX has a solid state controller that switches the fuel pump between 3 different flow / load settings.

There is some debate about whether the fuel pump is making full flow due to not getting full battery voltage, so that is correct in that at full throttle high boost the fuel pump may not keep up pressure/flowrate as both drop if supply voltage drops.

Running the fuel pump at full battery voltage may work, but will certainly reduce the fuel pumps life. It may also make it difficult for the fuel pressure regulator to hold design fuel pressure at low engine loads due to over supply of fuel. The problem discovered with the Walbro and the Link is that that fuel pump ( and maybe others ) has a thermal overload protection built in, and will cut out due to over temp if run at full supply voltage all the time, leaving you stranded in the middle of the street.

Given what we know right now, my suggestion is _IF_ you are seeing fuel pressure drop at WOT high boost, then you should consider an additional fuel pump power supply. Especially if your running N2O.

The most direct solution would be to place a switching relay in the fuel pump power supply line to the fuel pump, that switchs from the stock fuel pump regulator to a direct battery supply at WOT.

And yes if your fuel pump dies so will the engine, if it happens at WOT under heavy load, it could cause a fatal lean out detonation situation.

Larry
 
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