Thanks, I will and ill update with my results.

 

Fixed that missing bit; could that 12v source also be a direct feed off the battery (fused off course)?

I was flipping through NXP's catalog of Automotive MOSFETs, thinking these spikes should be planned in - theoretically.

 

Yah it sure could. I would probably just source it from the common side of the bypass relay since its already fused straight to the battery. Thanks for posting that catalog, ill flip through it, and im sure anything designated for automotive use should be designed to handle the environment, but a good look over the data sheets is a must.

 

Set up the majority of my rewire today, can' even tell it's there. Still waiting on the MOSFET findings, haven't terminated the coil feed.



Question though: How are you guys tapping into the actual 12V line that goes to the pump? Are you doing it inside the cabin or at the pump housing? -

Inside Cabin



Pump Housing

 

Ended up connecting to the fuel pump line in the cabin before it goes under the car. Wired everything, and blew the diode at the relay socket and the number 15 fuse. Must have either had the diode in the wrong direction, or it wasn't strong enough for the carrier signal. Removed the diode from the circuit, swapped the fuse and was good for idle.

 

Nice, yah a backwards diode basically becomes a short so that would make sense. How did you end up wiring up the relay?

 

Attachment 326947

Went with the possibility for a feedback loop, it seems specific enough that I'll be fine. I'll try out the MOSFET/10k once figured out, I'll I'd would need is add one additional 12 AWG wire, reconnect factory relay, and tap ECU 55.

 

mrfred- I love this solution! My only concern is splicing into the factory power wire. Isn't the factory wire too thin of a gauge to handle the higher output to begin with? I think I saw someone taking the larger gauge power line going directly into the housing, using a grommet, directly to the pump + connector. That was on a hard-wire set up, but just curious. (slightly off topic, but had seen a couple of rewires melting the wiring, one was my install. Scared me.)
Have you tried this method and for how long? I'm excited to try it, but dealing with melted wires previously has me gun shy. Thanks!

 

The best proof that nothing will melt is that people have been doing fulltime hardwires through the factory pump power plug for ages, and that is certainly the most demanding test of the factory wiring and plug.

 

Can this solution be used in the Evo 10? I would like the high voltage be supplied by the battery. So I want the pump to continue to be supplied by the factory low voltage side via the resistor, then when it switches to the high voltage activate the relay that has been hard wired via the battery.


I am seeing a number of wiring diagrams, which one would best suit my needs, and do what I am describing above?


I also read that you were having issues, I think regarding a fuel pressure spike, was this resolved?


I see in ECUFlash I have Min load for fuel pump high voltage, and fuel pump low/full voltage hysteresis. Will these tables need to be modified? I wouldn't think so.

 

Yes, it would work fine for an Evo 10 as well. The wiring diagram is so simple that I didn't bother posting it. To summarize though, its very similar to a traditional hardwire but with two differences:

1) Put a pressure switch inline with the wire coming off the battery. I recommend the pressure switch sold by SpoolinUp.com.
2) Splice into factory power near the pump power plug rather than cutting the wiring.

Also, don't forget to splice in some additional grounding. That's just as important as the power.

The other question that goes for a standard hardwire or this hardwire is where to run the wiring. I think a lot of people just run it under the car. This is definitely super easy, but be sure to protect the wiring with some kind of loom or sheath.

I never had an issue with pressure spikes on the stock FPR for any reasonable setting on the low/full voltage table. Note that I did substantially alter the low/full voltage table. I think it needs to be done even for something like a W255 upgrade.

 

Question, why the need of the pressure switch? I was thinking I could cut here, where I put the RED SQUARE, from there wire the hardwired 12v from the battery, and splice it in the 12v wire going into the intank fuel pump like you said. I had no plans on cutting it, but splicing it.


I know someone mentioned that there is a problem with this configuration with the pump running afterwards if you turn on, and then off the car, but has anyone confirmed a diode would fix that situation?





In other words like this + a diode


Another way,

I am still curious why I can't just CUT Pin 51, and just wire that to a relay to trigger?? That would be just soo simple. Do I need to have Pin 51 be part of that relay circuit, and only cut it where I put a red square to make it work rather than at pin 51? It looks like there is a number of ways to skin a cat here. I am just curious why it wouldn't work. If this would work, how would the relay configuration be?

 

You could cut pin 51 in your diagram to trigger your own high side circuit, you just need to make sure the current draw from your relay trigger isn't more then the ecu can handle. You will also lose the factory high side circuit in the process. If you just tap into 51 to drive the additional relay you will be increasing the load on the ecu by a large amount. You will want to wire your relay into the pump harness as close to the the pump as possible otherwise you defeat the purpose if your going through the factory wires.

 

Because what would be the difference really if I were to cut 51, and or cut where I put the RED box after relay number 1? Does 51 really have to be part of that circuit?


I plan to splice the 12v fuel pump line at the plug, bypassing most of the oem wiring. Like suggested in the Diagram I posted of the Evo 9 wiring.

My concern is where should I wire it to trigger. I can wire it after the relay and cut where the Ev0 9 guys cut, and where I put the red box in the Evo 10 diagram. Why would it matter, and what would be the difference?


I don't think using pin 51 to trigger a relay will be a problem. This guy is splicing into it, not even cutting to run another pump at high voltage while also keeping the stock intank both low, and high intact. But his diagram of how to wire the relay has me a bit confused.
http://www.evoxforums.com/forums/showthread.php?t=59151


Cause he is wiring the relay like this. It seems *** backwards to me. Should 86 be ground, and 30 fused battery 12V, he has 87, and 85 swapped it seems like. I don't see why both the relay configuration for the Evo 9, and this differ. They are essentially doing the exact same thing lol. I am all confused. Like why is 86, and 30 tied together? So your telling me fused 12v from the battery I am suppose to connect to 86/30, when I thought terminal 86 was a trigger. My relay knowledge is very limited, I know there is a number of configurations you can use them, I am trying my best to understand, and gain knowledge.



If he can splice into 51, and drive and trigger another relay that is wired to another pump, why can't I just cut 51, and drive that same relay, but instead of having it wired to another pump for high voltage just splice the line back into the intank 12v down at the plug level.


Has it been determined, is 51 a ground signal correct?

 

As you said, a power diode would be needed to prevent backwards current flow from the power side of the relay keeping the control side of the relay from deactivating, but yes, it can work.

Definitely a few ways to skin a cat, but after tinkering around with this a bunch, my conclusion is leaving all the factory wiring intact and using a pressure switch is the easiest way to get through this.