Quick Q about "necessity" of 12V Fuel Pump Mod!?

[rcsupra]

Hello all,

Well I discovered last night that my pump is going out from the noticeable death whine. The car will not be driven until I can get a new Walbro 255lph pump which I will be ordering right after I type this.

Here is my question though. I have been searching and reading just about every thread on here about the Walbro install/12V fuel mod (drjonez, forcedtorque, etc), and I am wondering if it is necessary for my setup. Some say it has its benefits, others said it is useless altogether or for certain setups, so I'd like your opinion!

I have a 50-trim CT26 on stock injectors/ECU/pump, everything. The most I will do from here on out is possibly 550 injectors with a LexAFM or MaftPRO, but I will not be upgrading to a larger turbo and all I want is low/mid-300's MAX out of this setup (285whp now).

What are the real benefits of the 12V mod, and do I need to do it in my particular case? Given my current setup and future plans, I'd like to keep it simple and avoid the rewire but I will look into doing it if it is only absolutely necessary. Thanks!!!

 

[teedoff00]

I don't know if it is an absolute necessity, but from what I hear the stock fuel pump is only ran on 9V or so. So obviously if you run a 12V fuel pump ie the Walbro, then you should re-wire it so it can get the voltage it needs. I had a Walbro ran off the stock setup for about a year and then it died. So I re-wired the new one because I figure it might last a little longer on the correct voltage. Not to mention the added benefits of operation.
The re-wire does make it a heck of a lot louder though!!
Good Luck!

 

[shaeff]

Makes tuning the car MUCH easier, as you're not tuning around a voltage switch that depends on several different variables.

 

[IwantMKIII]

Makes tuning the car MUCH easier, as you're not tuning around a voltage switch that depends on several different variables.

this


if you've ever datalogged AFR's you'll notice a strange fluctuation in the fuel curve typically around 3K, this is when the ECU decides to switch over to 12v. This mod eliminates this curve, which can happen at any RPM

here's an example of an old dyno graph i have before 12v, take notice the rapid change in AFR around 3K (keep in mind some of those lines are boost level curves):

 

[rcsupra]

Thanks for the replies!

I have now gathered from here and from speaking with others why people do the 12V mod, I understand it is to give the Walbro the necessary power to flow its rated peak amount of fuel. I see what you mean about tuning, and I know doing this mod would put me well on the safe side on my AFR's.

But I guess my question now is, do I need to do it? I spoke with a DSM friend running a non-rewired Walbro 255lph on 4x650cc's and he said his car is running fine, PLX Wideband shows its safe, and his car has had this setup for 3 years.

On my car, stock fuel everything with possibly the plan to go 550's, a couple extra pounds of boost on my setup (50trim CT-26@13psi), do I need to do the rewire? With those possible future plans, would the 550's duty cycle be high enough in the upper rpm's to necessitate maximum flow from the Walbro @ 255lph?

Thanks!!!

 

[teedoff00]

Like everyone said, you don't NEED to do it, but it will make you life easier when tuning. I think it makes the pump last a lot longer as well. The rewire will take maybe an hour to complete. It is WELL worth the time, not to mention it only costs like 20 bucks to do.
Great mod for the money/time imo.

 

[ForcedTorque]

Shaeff's write up was so easy to do , that even I could do it in my write up. He didn't mind my questions either. My pictures should show just how easy it is. I was a wiring virgin going into this car. Now it doesn't scare me a bit. It's you $100 pump. You gotta cut the wires inside the tank, so you just need to cut the same two wires on the outside, and hook them up to the relay. The pictures in my thread should take all the unknown out of it.

 

[deabionni]

I thought about doing the 12V mod, as I upgraded to a Walbro when my stock pump died on me. I just have two questions though.

1. Do you need an AFPR before doing this mod, or can the stock FPR keep the car from running rich with the extra pressure at lower RPM's?

2. The stock fuel pump relay & resister are up front, under the engine bay. How hard would it be to tap into the fuel pump wires right there, and add the relay under the hood instead of having the wiring & relay in the trunk?

 

[jdub]

I would get an AFPR...guys have installed a Walbro without one, but always seem to run into problems later.

If you just want to keep the pump at a constant 12V, you don't need a relay...just use the stock one. All you have to do is jump the resistor connector on the harness side to remove it from the circuit. Use wire at least the same gauge or larger than the harness.

 

[deabionni]

Thanks Jdub. I always thought there was a "cleaner" looking way to get a constant 12V to the fuel pump.

 

[jdub]

I am going to replace the wiring to the pump...10GA direct to the battery (re-located in the hatch area). I'm going to trigger a 30A Bosch relay with the stock wiring. The reason for this is to prevent a voltage drop (especially under boost) from using the old, small gauge wiring to run a high output pump. If this happens, the motor can go lean and go BOOM...just a heads up, so no whining.

 

[shaeff]

I am going to replace the wiring to the pump...10GA direct to the battery (re-located in the hatch area). I'm going to trigger a 30A Bosch relay with the stock wiring. The reason for this is to prevent a voltage drop (especially under boost) from using the old, small gauge wiring to run a high output pump. If this happens, the motor can go lean and go BOOM...just a heads up, so no whining.

That's exactly what I did, using the stock wires to power the relay, with dedicated power and ground wires to the pump.

 

[rcsupra]

Thank you for the help!

My next step is that I suppose, with a 12V Walbro, I need a new fuel pressure regulator to replace the stock one.

I think I'll be getting the Driftmotion complete kit...they seem to do a nice job of getting everything sorted correctly. I've been giving myself a headache trying to piece everything together, when I'd gladly pay for what they have to offer.

 

[rcsupra]

Another quick question...

After reading a few different 12V mod threads, these are all the parts I need, correct?

12 volt 30amp relay, 4 or 5 pin
10 gauge wire
12 volt fuse

I'm an electrical/wiring n00b, so when I went shopping I saw about a dozen different kinds of fuses. Could someone post up a pic of what I need to get? Thanks.

 

[ForcedTorque]

Check out the picture below. You will need some butt connectors (yellow box on bottom) at the tank, where you cut the existing wires, and connect the new wire in. They are very easy. You strip the end of the 2 wires, and stick one in each end, them crimp each one with the black wire crimpers. Next you will need a ring connector to connect your wire coming from the battery to the part where you should have a nut/bolt to bolt it to. Then you will need some male and female spade connectors to connect to your relay, and the male to make a jumper wire for the fuel pump relay.

I have several pictures in my tech thread to show you everything you need to do. I was every bit the wiring newb as you when I did it. I just took pictures along the way, and was very proud of all I had learned when I was through. I was ashamed at how long I was scared of wiring, it's so damn easy.

 

[Sil]

Check out the picture below. You will need some butt connectors (yellow box on bottom) at the tank, where you cut the existing wires, and connect the new wire in. They are very easy. You strip the end of the 2 wires, and stick one in each end, them crimp each one with the black wire crimpers. Next you will need a ring connector to connect your wire coming from the battery to the part where you should have a nut/bolt to bolt it to. Then you will need some male and female spade connectors to connect to your relay, and the male to make a jumper wire for the fuel pump relay.

I have several pictures in my tech thread to show you everything you need to do. I was every bit the wiring newb as you when I did it. I just took pictures along the way, and was very proud of all I had learned when I was through. I was ashamed at how long I was scared of wiring, it's so damn easy.

Any advantage to using crimp connectors vs just soldering the two wires and shrink wrapping them? As soon as my gas tanks empty its getting dropped for the new pump.

 

[shaeff]

A properly done crimp connection will have less resistance than a soldered joint. That being said, I solder most things.

 

[Quin]

It's easier to use crimp connectors, and if you need to redo it or undo it later it's easier to replace a crimp connector than resolder it. Most people have never soldered before, and don't have a soldering iron, which adds to the complications. As far as conductivity is concerned, either should be fine.

 

[rcsupra]

Another quick Q, and thanks for the replies and help so far! ForcedTorque you've been invaluable.

So I've gone to Advance, Autozone, Circuit City and WalMart looking for a 10 gauge wiring-fuse holder, or even a universal fuse holder, with no luck. So I bought a 12 gauge fuse holder, knowing that the thinner wire would increase resistance and that the fuse would probably fail before the wiring. So would you recommend waiting until I can order a 10 gauge holder, or would you think its OK to just crimp the 10 to the 12 gauge at this fuse holder? Thanks

 

[tlo86]

Another quick Q, and thanks for the replies and help so far! ForcedTorque you've been invaluable.

So I've gone to Advance, Autozone, Circuit City and WalMart looking for a 10 gauge wiring-fuse holder, or even a universal fuse holder, with no luck. So I bought a 12 gauge fuse holder, knowing that the thinner wire would increase resistance and that the fuse would probably fail before the wiring. So would you recommend waiting until I can order a 10 gauge holder, or would you think its OK to just crimp the 10 to the 12 gauge at this fuse holder? Thanks

did you ask the guys that work at the parts store? what was it, a 30A in line fuse IIRC?