Turkeylord

I'm using the original LGT module. Part numbers for STi modules are listed in the other thread, however there is some discrepancies in which year STi and what part number people are using. IMHO, the wiring is the main problem with the system.

Great point. Just doing a little exercise in the maths... Assumptions: 30' of wire in the circuit, DW65c pulling 11.65A@45psi, 13.8V alternator voltage, ignoring connection losses. You could expect to see: 18awg: 11.84V 14awg: 12.95V 12awg: 13.25V 10awg: 13.45V So even with 14awg you'd pick up over 1V. I had the 10awg Green/Yellow laying around so I went with that.

Thanks Shawn!

Heat shrink would be better, but would likely require cutting the stock wires to install. I preferred just stripping windows in the stock insulation in this instance. It's a trade-off for sure. Thanks for the feedback.

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:

Some have upgraded the module itself to an STi module which performs slightly better. Others have also upgraded the factory harness ends to the larger gauge STi/WRX units. All the relevant information can be found in the original thread here: http://legacygt.com/forums/showthread.php/fuel-pump-control-module-143860.html

Walkthrough is up and your feedback is welcome. Thanks everyone! http://legacygt.com/forums/showthread.php/upgrading-your-fuel-pump-wiring-4th-gen-213570.html

Step 3: Wiring. You'll need your wire, your soldering iron, and plenty of electrical tape. Fish your wires from one access panel to the other. I put mine in a piece of loom to protect them down there. Wires near the fuel pump. Strip windows in the stock FP wiring. The wires you need are the Green/Yellow (positive ) and the Green/Red (negative ). Strip the ends of your 10 awg wire and tin everything with your soldering iron. Make your connections. I use zip ties for strain relief. Tape everything well and plug it back in. Wires on the other side and the stock grommet. It took some convincing, but with the wires cut at an acute angle, some tape and some spit-lube, I got them through the stock grommet. Run your wires back towards the FPCM. I followed the stock harness. Strip a window in the stock negative lead (Green/Red), tin your wires and make your connection. Do the same for a ground lead on the black wire. Your positive wire will go to a relay. I used a relay socket and salvaged the pins to go onto my new wires. Pin 30 to fused battery power, pin 87 to fuel pump positive, pin 85 to ground and pin 86 to the Red/Black at the FPCM. Terminate your FPCM ground and relay ground with a ring or fork and ground them. I crimped and then soldered this connection and used a factory ground location. Unplug the FPCM plug and remove the Green/Yellow. Pry up the white retainer, then un-pin the terminal. I loomed the harness back up and taped the terminal to it making sure it was well covered after this pic was taken. Plug your FPCM back it and re-mount it in the quarter. Secure the relay and connect it to fused battery power. After trying to fit the trim panels, I wound up moving the relay to the other side of this panel so it was inside the quarter. Put the interior back together, re-connect the battery and that's it! This mod has been done a number of ways, this is just one of them! HUGE thanks to everyone in this thread for their outstanding work figuring out how to do this. I'd especially like to thank Scooby2.5, KCwagon, Frank_ster and coldsubycz for their helpful posts in that thread!

***Notice*** It has been brought to my attention that this mod as shown may cause a small current drain, possibly due to an indirect ground connection through the FPCM. Please see the following thread for more information: http://legacygt.com/forums/showthread.php/fpcm-wiring-upgrade-relay-staying-switched-w-key-off-242295.html When I have time to diagnose/fix the issue on my own vehicle I will update this guide. ***Notice*** This is a walk through guide to upgrading your fuel pump wiring. The OEM wiring is small and experiences significant voltage drop by the time it gets to the fuel pump. Upgrading the wiring will help deliver more volts to the fuel pump and help it run better. For general questions or alternate methods regarding upgrading the fuel pump wiring, please post in this thread! This install was done on a 2005 Subaru Legacy GT Wagon, YMMV. Follow these instructions at your own risk. Sorry sedans (not really sorry). Step 1: Remove interior pieces. You will need to remove a bit of interior to gain access to the fuel pump (FP) and fuel pump control module (FPCM). Disconnect the battery. Remove the rear seat bottom. It just pulls up from the front in two places. Remove the driver's side seat bolster piece, where the seatbelt lays. There is one 12mm bolt at the bottom, a couple clips, and a tab slides out of the top of the rear trim panel. I left the seatbelt in place and just swung this piece out the door, but you can unbolt the belt if you'd rather. Remove the rear carpet sections. Spare cover, left and right pieces. They should lift out easily. Remove the tray, tools, and spare. Optional, but more room to work. Unclip and flip up the front foam piece, and remove the drivers side foam piece under the carpet. Remove the D pillar cover. Remove the rear trim panel. This is held on by 5 screws and some clips. Screws are located under each of the tie-down hooks, the D pillar, the bag hanger and the tonneau mount. The seatbelt goes through here too, unbolt if you'd like. Step 2: Gettin' ready. You'll need ~10 feet of wire for both negative and positive leads to get back to the FPCM. I used 10 awg wire. You will also need to get battery power - I used my (yet to be installed) amplifier power wire. You could run another length of 10 awg to the battery, just be sure to fuse it properly. Remove the fuel pump cover. You'll also need to remove the cover on the driver's side. Open up the clip holding the harness to the tank, this will give you a little slack. Unwrap the end of the harness. Close-up of the stock wiring. Unmount the FPCM. It's tucked up into the driver's rear quarter. Harness moved to show the mount. One 10mm nut and a tab that slides. Free at last! Close-up of stock wiring. 4th Gen Legacy GT Fuel Pump Wiring Upgrade - Turkeylord 9-5-2013 w-wiring diagram, parts lists, .pdf

So, problem solved. It was a combo of needing to disconnect the green/yellow from the FPCM and using the red/black to trigger the relay. Works great now.

I'll give it a try again. I think it's back-feeding through the green/yellow and keeping the relay engaged. Well get'r figger'd eventually... *edit* I think my main problem is I need to cut the green/yellow at the FPCM. Should be easy enough to jumper and find out.

I'm using the green/yellow FP+ off the FPCM to power the relay. Both it and the red/black and ignition switched and show the same behavior, I tried it with the red/black temporarily.

So I ran into an issue. Added the relay tonight. Problem is it clicks on fine, but then it's latched on, and won't turn off with the key... So I need to noodle on it for a while and figure out what I need to do. Pull a switched +12 for somewhere else for the relay maybe?

Sent new logs to Bren to see if it made a difference, he replied: Guess I should've done this a long time ago, d'oh!

I just did this today. I didn't take any voltage readings yet, but I can tell just by the sound of the thing that it's working better. *edit* I did take lots of pictures, I just need to finish up the install, take the last few pics and get it written up.

If/when I do this I'll try to take some good pictures and we can do a write up.

Thanks KCwagon, Scooby2.5 and Frank_ster for your helpful posts in this thread! Bren isn't happy with my DW65c, so I think I'm going to try this before switching to something bigger. Now that we understand the system better, has anyone tried the wiring upgrade with the OEM FPCM? My other thought was that this might even be enough with the OEM pump for those borderline situations like a 16g on gas...

That was quite the well thought out and elaborate test. Was there a large volume of air escaping? It didn't sound like too much from the video, at least compared to the volume of air that would be going into the engine at that point. It wouldn't be easy to replicate your test on the older style BPV, but maybe I can come up with something...

I'll bite. So, how would you verify that it's leaking? My boost stays right on target (maybe even a little overboost at the peak) all through the pull, so I don't think logs are going to help. Disconnect the recirc hose from the BPV and clamp it off, try to listen for leaking in the middle of a WOT pull? A nice Forge BPV has been on my wishlist for a while, I just haven't seen any evidence that I need one so far. Thanks for taking my call, I'll hang up and listen...

+1, holding 21-22 PSI here on the stocker...

Nice! What turbo?

Anyone else going to the Ojibwe Forests Rally next weekend? http://mnsubaru.com/threads/ojibwe-forests-rally-%E2%80%93-august-23-24-2013.43672/

PA gear, a canopy and a generator... http://i.imgur.com/J89qC3ll.jpg

Built like a tank, nicely done.

Thanks Trapping 110 would take another ~45 HP or dropping a bunch of weight. A 12.9@106 should be doable with some cold air. Stock clutch is the weak point for harder launches now.