Upgrading Your Fuel Pump Wiring (4th Gen)

My DW kit has the blue (direct to batt) and yellow (FP+) in the same place as SBT's pdf.

The difference is the DW black wire is pin 85 and the white (with black extension) is pin 86 and the DW instructions state that the black wire goes to stock relay/FPCM B+ and the white wire is the ground.

In SPTs diagram pin 85 is the ground and 86 is the stock relay FPCM B+.

I just want to confirm if the pin numbers are arbitrary and I should just follow the DW instructions. or maybe my DW relay wires were swapped at the factory?

I should also mention that if your fuel pump was struggling to keep up on the factory wiring, this upgrade may affect your tune!

 

I sent new logs to Bren after the upgrade to see if it made a difference, he replied:

Sorry to necromance this thread, but thought it was relevant over just opening another one. How can the re-wire make you go rich unless you are outflowing your pump? (I do realize that was the caveat you put in so maybe that's the answer). As long as you have good pressure and are under the flow limits of the pump, the ECU and injectors should be the ones taking care of the mixture, not the pump? Or is there a piece I'm missing?

For example, if I have an AEM 340lph and I've estimated my peak fuel needs to be about 181lph (ID1000s at about 74% IDC on e85 targeting 11.6AFR, 21psig in Denver, 17psig compared to sealevel and 12psig at redline compared to sealevel), re-wiring shouldn't affect my tune if I have good base pressure and my pressure is rising 1:1 with boost right? Even if my pump were flowing less due to the factory wiring, I should still have plenty of fuel as long as pressure is behaving as it should?

Sorry to necromance this thread, but thought it was relevant over just opening another one. How can the re-wire make you go rich unless you are outflowing your pump? (I do realize that was the caveat you put in so maybe that's the answer). As long as you have good pressure and are under the flow limits of the pump, the ECU and injectors should be the ones taking care of the mixture, not the pump? Or is there a piece I'm missing?

 

For example, if I have an AEM 340lph and I've estimated my peak fuel needs to be about 181lph (ID1000s at about 74% IDC on e85 targeting 11.6AFR, 21psig in Denver, 17psig compared to sealevel and 12psig at redline compared to sealevel), re-wiring shouldn't affect my tune if I have good base pressure and my pressure is rising 1:1 with boost right? Even if my pump were flowing less due to the factory wiring, I should still have plenty of fuel as long as pressure is behaving as it should?

It can't -if your fuel pressure is correct and not falling below the regulator pressure, it won't change anything.

If your fuel pump (for whatever reason) can't keep up with the flow and pressure demands - generally at high load/rpm, fuel pressure will drop, and IDC would have been increased to compensate. Unless you're watching fuel pressure live as you do this, you don't know (but you could probably calculate it).

Obviously if you fix the fuel pressure/flow issue, your IDC is now increased vs what it should be, and you will run rich.

I've just done this modification myself:

Bring this thread from the dead...

I just picked up a spec B and want to confirm a few things. I am considering two routes currently:

FIRST, E85. It looks like if I want to go to a bigger pump to support E85 on a 16g with 1050x ID injectors (probably AEM 320/340 E85 pump), and possibly the Cobb Flex Fuel kit, what is the best way to accomplish?

The DW pump wire kit, it directly wires to the battery, I don't need to connect it to any wiring in the car right? So it will be a independent of the car's wiring and the pump will just be on 100% duty at all times, correct?

SECOND option, don't bother with E85 and then go with 16gb DW65c pump at some 750cc top feed injectors (or should I just go with 1050x anyway), and I don't have to worry about the pump wiring?

Thanks in advance!

What I found with my buddies spec b was the fuel pump wiring to and from the control module and the pump etc was the same size as an STI. So with that info I would just drop in the AEM 320/340 pump and be done with it.

I was the first to discover the small wiring in the legacies but when I went to help Zero1 with his install we found the wiring the same as an STI.

I now have a 2013 STI and I just did a drop in AEM 320/340 pump. Got it off Amazon for $100-115.

Really no need to use the DW kit with a spec b or STI because the wiring is enough to handle without a voltage drop

Anywho, not sure if anyone shared this

https://www.iwireservices.com/product-page/fuel-pump-controller-plug

Makes it a lot easier to just crimp your own 10 or 12 gauge wire, rather than trying to mess with already crimped and skimpy wires.

Anyone know where the best spot to put a kill switch would be? I figured on the line coming from the battery before the fuse, but I still think the stock wiring would work, which makes it pointless.

I'm not sure if the power/signal coming from the stock relay is bridged with the power of the other relay or if it's just used to send a signal to close the circuit. Any electrical engineers.... i'm a me who hates electricity....

Anyone done this before?

I figured why not toss in a 2 dollar switch to kill the fuel pump for when you park in those "shady" areas. Pop the trunk flick the switch and now bad guys have to work extra hard to steal your ride.

why would they put a thicker gauge wire on the sti/wrx vs the lgt....

I was looking for a pigtail for the fpcm after I butchered mine trying to shove 10awg wire into these skimpy 18awg looking terminals and started to panic, so i contacted my parts guy at north coast subaru in long island, and he found one laying around that was used, this dude always comes through in the clutch!

It looks like a much thicker wire than our lgts. I ordered them both, the used and iwire connectors, because he shipped it to me for 10 bucks, so why not!

Poor form subaru....

And these iwire people have one for the other end as well!!! Looks like they have EVERYTHING!!

https://www.iwireservices.com/product-page/gas-tank-plug-newer-model-subaru

So hardcore 10awg all the way! I don't see how tapping in would be healthy for that little gauge line. But then again I didn't do any math so I just cut the math out and just remove the issue.

I had these relays for something else, but the wire gauge wasn't what i wanted.

https://www.amazon.com/Support-Relay-Spst-4pin-Socket/dp/B00RWWZ7P2

Luckily they had simple common connectors and were easy to rewire

So everything 10 awg.