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Old 02-22-2005, 02:17 PM   #1
n2xlr8n
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Default Hydra...fuel pump controller-less?

I want to create my own fuel system for my project. Speaking with Phil a while back, he seemed to think that the Hydra will manipulate the stock FP controller in the same fashion as the stock ECU (however it does that). I want to make my own fuel system, independant of the Hydra, with -8 supply, and -6 return, relay or relays providing the power, etc..

Any input?

Thanks!

Steve
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Old 02-22-2005, 02:26 PM   #2
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your return should be the same size as the supply, or in some cases bigger..
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Old 02-22-2005, 02:55 PM   #3
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You know I looked at my Hydra harness the other day just to make sure I wasn't wiring anything extraneous or missing anything in the harness I'm building.

The fuel pump controller has two wires going to the stock ECU, but the Hydra only uses one of the wires. A13 I think on the stock ECU. I believe the ECU grounds those pins, the FPC gets its power from the fuel pump relay. If the Hydra only grounds the one pin it may cause it to just run at 12v all the time. I seem to remember there being problems with the Link ECU because it did the same thing, it would burn out the fuel pump. Maybe I looked at the harness wrong, but I don't think so. Maybe the second pin is feedback from the FPC to the ECU and it's something the Hydra just doesn't use.

Either way I don't think the Hydra cares. I may end up doing this in my car, just wire the pump directly to the fuel pump relay since I don't even have a fuel pump controller at this point. The WRX pump isn't meant to be run at 12v continuously though.

Last edited by dwx; 02-22-2005 at 03:04 PM.
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Old 02-22-2005, 05:51 PM   #4
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Quote:
Originally Posted by Yeah baby
your return should be the same size as the supply, or in some cases bigger..
I'm afraid I don't understand.....I've used that very setup on my cars for years....one of which made over 1100 hp (-12 to pump, -10 to fuel log, and -8 return). Please explain.

If that's what Corky Bell said, I'll pass.
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Old 02-22-2005, 06:43 PM   #5
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Quote:
Originally Posted by dwx
Either way I don't think the Hydra cares.
That's great info, dwx.

So to make sure I understand: You think that instead of ramping the pump voltage, the Hydra CPU provides the ground for the pump relay, allowing the full 12 or 14v to the pump? Thanks for your help!

Steve
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Old 02-22-2005, 07:12 PM   #6
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I have a fuel pressure gauge in my car. At idle, the fuel pressure is higher than with the stock ECU (closer to 50psi/3.4 bar with the FPR vacuum hose unplugged). So, it LOOKS like the fuel pump may be getting 14v at idle....

IMO its a good thing
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Old 02-22-2005, 08:32 PM   #7
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Quote:
Originally Posted by DarthChicken
IMO its a good thing
Me too.

It will make installing a fuel system much easier, and I don't have to worry about the ECU tinkering with it.
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Old 02-22-2005, 09:39 PM   #8
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n2xlr8n ..I'm guessing your setup was on a carburated car..FI cars with high power fuel pumps are different.. I have basically the same setup on my BDS blown 460 SBC even with twin dominators there is only 12 psi out of the twin holly fuel pumps.Not 80+psi out of a FI fuel pump...
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Old 02-22-2005, 11:43 PM   #9
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Quote:
Originally Posted by DarthChicken
I have a fuel pressure gauge in my car. At idle, the fuel pressure is higher than with the stock ECU (closer to 50psi/3.4 bar with the FPR vacuum hose unplugged). So, it LOOKS like the fuel pump may be getting 14v at idle....

IMO its a good thing

Did you use a Link ECU in the past? I thought there was an issue in the past with running the variable voltage fuel pumps at 12-14v all the time.
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Old 02-23-2005, 02:42 AM   #10
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Yes, I did run a link before.... and yes, I did occasionally have the fuel cut problem. No issues here though
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Old 02-23-2005, 09:58 AM   #11
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Hmm I guess in my case I may just wire the Hydra output directly to the fuel pump relay instead of bothering with the fuel pump controller, if it's just going to run the pump at full voltage all the time anyways.
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Old 02-23-2005, 11:16 AM   #12
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Quote:
Originally Posted by dwx
Hmm I guess in my case I may just wire the Hydra output directly to the fuel pump relay instead of bothering with the fuel pump controller, if it's just going to run the pump at full voltage all the time anyways.
dwx, would you be so kind to let us know how that works out? That is exactly what I'd like to do, but I'm still a few months out on this.

Thanks for the help, folks.

Steve
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Old 02-23-2005, 11:50 AM   #13
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Sometimes I just love reading speculation.

The Element Hydra WRX unit controls the fuel pump controller like stock (variable duty) even thought itís not exactly the same. I see about 40 psi at idle instead of the 38 psi I see with the stock ecu. Your pump control unit always sees 13-14 volts and then the signal is grounded (waveform) to give you the variable duty.

I say why mess with a good thing. We don't see fuel pressure taper until 475 whp running a Walboro 255. Event then you can just increase the injector pulse width to compensate.

Thanks,
Phil
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Old 02-23-2005, 12:13 PM   #14
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Thats why I said "LOOKS" like it might be 14v... I put up a post at www.carmodifications.com to see what they would say as well Phil, as you hadn't posted to this thread yet.

Wasn't sure if you knew or not either... you'd think I'd learn to stop doubting that by now
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Old 02-23-2005, 12:16 PM   #15
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Quote:
Originally Posted by Element Tuning
Sometimes I just love reading speculation.

The Element Hydra WRX unit controls the fuel pump controller like stock (variable duty) even thought itís not exactly the same. I see about 40 psi at idle instead of the 38 psi I see with the stock ecu. Your pump control unit always sees 13-14 volts and then the signal is grounded (waveform) to give you the variable duty.

I say why mess with a good thing. We don't see fuel pressure taper until 475 whp running a Walboro 255. Event then you can just increase the injector pulse width to compensate.

Thanks,
Phil
www.elementtuning.com
Do you know what the two connections to the FPC do on the stock WRX? I swear I looked at the Hydra harness and it only had a connection to one of them.
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Old 02-23-2005, 06:39 PM   #16
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Quote:
Originally Posted by Element Tuning
Your pump control unit always sees 13-14 volts and then the signal is grounded (waveform) to give you the variable duty.

We don't see fuel pressure taper until 475 whp running a Walboro 255.

Thanks,
Phil
www.elementtuning.com
Are you saying the factory pump controller outputs a PWM signal to the pump?

If my setup doesn't eclipse that mark, I'll park it and drive my Echo

Thanks for the help.

Steve
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Old 07-07-2005, 03:09 PM   #17
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Sorry to bring this back from the dead... Anyone did anything at with this issue?
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Old 07-07-2005, 07:15 PM   #18
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I just tuned a built STI yesterday to 450 whp on pump fuel with an Element Hydra. His fuel system was about as good as it gets but we still ran out of fuel injector. He was using UR 780 and I was trying to maintain an 11.6 AFR around 23 psi.

First off he had a Walboro 255 in tank pump feeding a surge tank (2 quarts?) and from there an Aeromotive (this thing was massive) feeding -10 AN lines all the way to the fuel rails with -8 AN lines feeding the rails themselves. I believe this terminated in an Aeromotive regulator with -6AN return lines. In any event, he wasnít exactly sure how they (Quantum Racing) had configured the wiring for his pump but this is what he suspected. The Aeromotive pump was tied into the stock pump power but also had a relay with power directly from the battery (but Iím not sure exactly how this was done). It was definitely tied in because primed and turn off when the ignition was turned on. I suspect the Aeromotive pump ran at full duty when any current flowed to the stock pump vs. a variable duty.

The moral of the story is to put 1000cc injectors in your car or all the pump is going to do is make your car noisy. LOL!

Thanks,
Phil
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Old 07-07-2005, 08:48 PM   #19
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Hey, I bet this is one of the local Dayton guys. Sounds like I need to track him down for a ride to see what the 450hp feels like. Anyway what would you say is a good choice for 1000cc injectors for an STi? Also do you still feel the Walbro pump is the best choice or should we look for something with more flow?

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Old 07-07-2005, 09:09 PM   #20
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suscribed
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Old 07-07-2005, 10:05 PM   #21
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Quote:
Originally Posted by offset
Hey, I bet this is one of the local Dayton guys. Sounds like I need to track him down for a ride to see what the 450hp feels like. Anyway what would you say is a good choice for 1000cc injectors for an STi? Also do you still feel the Walbro pump is the best choice or should we look for something with more flow?

offset
For those who experience colder climates a single Walboro and 800cc injectors are just enough for the 375-400 whp on pump fuel and about 500 whp on VP C16. Keep in mind the AFR has a lot to do with the maximum achievable power for a given injector.

It will be interesting to see whatís capable with a single Walboro and 1000cc injectors. I know for certain that I was loosing around 1.6 psi of fuel pressure at 550 whp running 30 psi of boost pressure (70 psi fuel pressure). So even though fuel pressure will not hold constant, with all that head room running 1000cc injectors it would be interesting to see what sort of power could be supported.

At this point I do not have a recommendation because I havenít tested any of the 1000cc injectors as frankly Iím not looking forward to retuning our car. LOL! I can say now with conviction, bigger injectors will be my first step and not the pump.

Now if the goal is 650+ whp then a fuel pump solution is a must. A dual Walboro setup and 1000cc injectors should be a solid choice but may require running a stand-alone such as the Hydra for appropriate control. At this point I am still uncertain what path I will take.

Thanks,
Phil
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Old 07-07-2005, 10:30 PM   #22
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Thats good advice Phil.

What I found was the issue with a single walbro and 850's was that once you really started to run some boost the fuel pressure would get up to 70psi. At 70 psi the walbro starts to fade off in the flow dept. All fuel pumps do this.They flow the most at 0 pressure. I knew larger lines would help for sure. But I dont like running SS lines on a street car. So my simple solution was to simply use two walbros. At this point the investment is cheap and you get lots of flow at 70psi. You can use the stock lines and with this setup 525whp shows no fade in pressure. Great for the octational C16 Drag race fun and MORE then enough for Pump gas at lower boost/fuel pressures.

No doubt that larger injectors is a good way to go. But they are hard to find and if you need High imp units you are pretty much forget it. So what we are doing on a car we have at the shop now thats goal is 600-700whp is running 8 injectors. 4 stockers and 4 PE850's. The stocks will run up to 80% or so and then I will map the others in. Twin walbros is plenty as you have a ton of injector.

I bet that Aeromotive was loud!

Clark
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Old 07-08-2005, 09:16 AM   #23
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Thanks for the info guys!

Clark: What about the RC Engineering 1000cc low impedance injectors? These can definately be used with a stand alone capable of handling both low / high impedance injectors.

I "think" it is less work than installing 4 additional injectors. Indeed there is more tuning involved and specially in the idle/low boost area... but once done... it should be OK.
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Old 08-02-2005, 05:10 PM   #24
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My plan is to run a Denso Supra pump @ 14 vdc to a spare tire well surge tank, install -6 supply/return lines to my Perrin rails and Aeromotive RRFPR, utilizing modded WRX injectors.

I had emailed Pavlo a while back asking for pics of his fuel system, but he is slammed at work.

As a side note: Why would one be afraid of using SS lines for the fuel? I crashed one of my projects at 133 mph back in '94, and the fuel line was the only thing holding the differential in. Much safer than the stock plastic lines, unless of course you don't know how to make the AN connections. It's okay. I'm afraid of tornados.
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