GTTuner Posted August 19, 2010 Share Posted August 19, 2010 How many here have bypassed the fuel pump control module and replaced it with a relay when they did their Walbro install? Link to comment Share on other sites More sharing options...
f1anatic Posted August 19, 2010 Share Posted August 19, 2010 I would like to know that as well. Also please include any and/or all links to the said operation of using a relay. Link to comment Share on other sites More sharing options...
rao Posted August 19, 2010 Share Posted August 19, 2010 Making that change would be easy, but why would anyone do this? Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
GTTuner Posted August 19, 2010 Author Share Posted August 19, 2010 Making that change would be easy, but why would anyone do this? Thanks for chiming in rao. I figuired why run the pump at less than 100%? Why does Subaru do this? I just want smooth consistant fuel delivery from this pump before I tune since my IDC's are up pretty high. Your thoughts are apprecieated! ( Sorry, I'm going to make you type today:lol:) Link to comment Share on other sites More sharing options...
rao Posted August 19, 2010 Share Posted August 19, 2010 They do it to reduce the heating of the fuel and evaporative emissions. In a nutshell, the pump will run in 3 modes: 1/3 at idle or no load, 2/3 at low load and 100% at high load. There is ABSOLUTELY NO REASON AND NO BENEFIT to running the pump 100% at all times. Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
SubOperator Posted August 19, 2010 Share Posted August 19, 2010 Paul, have you looked into 08+ WRX & Sti pumps ? I was looking at 245lh ones AVO is selling for 05 LGT with variable voltage support, and they list it as compatible with 08+ Wrx, Sti and FXT. My thought was to get one of those and retrofit it into my LGT. I was wondering what the flow is on those pumps. Don't think I like the idea of fuel pump running at 100% capacity all the time. 2005 LGT Wagon Limited 6 MT RBP Stage 2 - 249K 2007 B9 Tribeca Limited DGM - 272K SOLD - 2005 OB Limited 5 MT Silver - 245K SOLD - 2010 OB 6 MT Silver - 205K Link to comment Share on other sites More sharing options...
holyjoetart Posted August 19, 2010 Share Posted August 19, 2010 +1. The life of your fuel pump will also be shorter. Link to comment Share on other sites More sharing options...
m sprank Posted August 19, 2010 Share Posted August 19, 2010 I have debated for a while installing a relay to make the Walbro get full power all the time. Only because the Walbro is not designed to run at different voltages. Sure any 12vdc electrical motor will operate at about 5-6 volts. Even many 110v motors will operate at less voltage (just hook them up to a light dimmer and watch). But I am hearing that the failures associated to Walbros (fewer than the rumors portray) are most likely due to feeding them low voltage and causing the motors to overheat and fail. Rao, any thoughts (honestly, not sarcasm). Link to comment Share on other sites More sharing options...
executor485 Posted August 19, 2010 Share Posted August 19, 2010 /subscribed... Interested to hear some real ideas and thoughts as I will be installing my walbro soon. If I pass you on the right, I'm flipping you off. Link to comment Share on other sites More sharing options...
GTTuner Posted August 19, 2010 Author Share Posted August 19, 2010 I have debated for a while installing a relay to make the Walbro get full power all the time. Only because the Walbro is not designed to run at different voltages. Sure any 12vdc electrical motor will operate at about 5-6 volts. Even many 110v motors will operate at less voltage (just hook them up to a light dimmer and watch). But I am hearing that the failures associated to Walbros (fewer than the rumors portray) are most likely due to feeding them low voltage and causing the motors to overheat and fail. Rao, any thoughts (honestly, not sarcasm). m sprank......exactly my thoughts on this. The OE pump is designed to run on lower voltage but can the Walbro stand up to this? sub op, I'll look into the Sti pump. Link to comment Share on other sites More sharing options...
GTTuner Posted August 19, 2010 Author Share Posted August 19, 2010 Another thought on this; Has anyone had one of the FP control units fail? Link to comment Share on other sites More sharing options...
Th3Franz Posted August 19, 2010 Share Posted August 19, 2010 The ECU can only deliver a limited amount of electrical power. If you put in a big pump or more than one that need a high current draw to reach its rated pressure, the stock ECU might not be able to supply enough juice. For now, on my friend's car with dual Walbros we have relays in place drawing current directly from the battery. I have a background in power electronics so I am designing a circuit that will use the stock fuel pump control to reduce the speed of the pumps for idle and low load situations. Why would lower voltage cause a motor to overheat and fail? -Franz The end of a Legacy http://www.youtube.com/th3franz Link to comment Share on other sites More sharing options...
John M Posted August 19, 2010 Share Posted August 19, 2010 NSFW has found the fuel pump duty cycle tables but right now it's not a standard definition. Apparently it's different in each ROM revision so he's got to manually locate it for each ROM. Once it's been made available for all ROMs, it's simply a matter of typing in 100% for all values -- no hardware change required. I'd want to do this even if I went to a relay so it'd have a steady trigger input. Link to comment Share on other sites More sharing options...
rao Posted August 19, 2010 Share Posted August 19, 2010 I have debated for a while installing a relay to make the Walbro get full power all the time. Only because the Walbro is not designed to run at different voltages. Sure any 12vdc electrical motor will operate at about 5-6 volts. Even many 110v motors will operate at less voltage (just hook them up to a light dimmer and watch). But I am hearing that the failures associated to Walbros (fewer than the rumors portray) are most likely due to feeding them low voltage and causing the motors to overheat and fail. Rao, any thoughts (honestly, not sarcasm). That is complete BS. Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
Th3Franz Posted August 19, 2010 Share Posted August 19, 2010 NSFW has found the fuel pump duty cycle tables but right now it's not a standard definition. Apparently it's different in each ROM revision so he's got to manually locate it for each ROM. Once it's been made available for all ROMs, it's simply a matter of typing in 100% for all values -- no hardware change required. I'd want to do this even if I went to a relay so it'd have a steady trigger input. I think the switching frequency is high enough where the relay stays closed but I haven't had a chance to measure it directly yet. I'm waiting on a high-speed DAQ card to do it. -Franz The end of a Legacy http://www.youtube.com/th3franz Link to comment Share on other sites More sharing options...
GTTuner Posted August 19, 2010 Author Share Posted August 19, 2010 Ok, so what is the benefit of running the pump at a lower speed anyway? Would this screw with latency settings if you went 100%? Link to comment Share on other sites More sharing options...
rao Posted August 19, 2010 Share Posted August 19, 2010 Would you like me to type this 100 times? THEY DO IT FOR EVAPORATIVE EMISSIONS REASONS. It will not bother your latency settings or anything else- don't *^$#$#$% with it Rob IF YOU CARE ABOUT YOUR CAR YOU SHOULD NEVER DRIVE IT Link to comment Share on other sites More sharing options...
GTTuner Posted August 19, 2010 Author Share Posted August 19, 2010 Would you like me to type this 100 times? THEY DO IT FOR EVAPORATIVE EMISSIONS REASONS. It will not bother your latency settings or anything else- don't *^$#$#$% with it I'm sorry to annoy you rao, I did not know that. Please type it one more time and make it 101 times. OK, so I won't (*&^#$(*& with it! Link to comment Share on other sites More sharing options...
m sprank Posted August 19, 2010 Share Posted August 19, 2010 Thanks Rao. I too questioned why the pump could not take the lower voltage. Not like its pulling more current. But you know how the interweb is. Lots of good BS to read. I have not had an issue with just hooking mine up to the OEM electrical connection. Just read a bunch of crap about possible causes of failures. If its good enough for Rob, its good enough for me. Link to comment Share on other sites More sharing options...
integroid Posted August 19, 2010 Share Posted August 19, 2010 So if I wanted to use a Weldon pump or a Fuel Labs pump, would it be best to wire it to a relay and let it run at 100% all the time or hook it up directly to the factory wiring? According to fuel labs, you can run their pumps without an external controller and it can be run on the factory wiring. I dont know how true that is. Link to comment Share on other sites More sharing options...
Th3Franz Posted August 19, 2010 Share Posted August 19, 2010 You could start by hooking it up to the stock wiring and see if the pressure is high enough for your needs, since the supply current from the ECU might be limited. If not, then you can run it with a relay and run it at 100% with current drawn straight from the battery. Fuel pumps can get pretty noisy running at 100% all the time though -Franz The end of a Legacy http://www.youtube.com/th3franz Link to comment Share on other sites More sharing options...
Sarg Posted August 19, 2010 Share Posted August 19, 2010 Actually the Fuel Lab pumps have a built in controller so that you don't have to run it 100% all the time. It does 66% at low mode and 100% at high mode that is switchable through any 0-5v source. Link to comment Share on other sites More sharing options...
Boostin1657615274 Posted August 20, 2010 Share Posted August 20, 2010 Does the fuel pump controller vary the voltage through resistors? Or is the pump somehow pulsewidth modulated? On the search for a new DD... Link to comment Share on other sites More sharing options...
utc_pyro Posted August 20, 2010 Share Posted August 20, 2010 (edited) TI have a background in power electronics so I am designing a circuit that will use the stock fuel pump control to reduce the speed of the pumps for idle and low load situations. How about just use the stock ECU PWM output to drive a power mosfet? You really have no reason to run the thing at 100% most of the time (it will DECREASE the life of the pump), just let the ECU do it's thing but with less total inline resistance fore the pump? Does the fuel pump controller vary the voltage through resistors? Or is the pump somehow pulsewidth modulated? It's PWM. Edited August 20, 2010 by utc_pyro Link to comment Share on other sites More sharing options...
Boostin1657615274 Posted August 20, 2010 Share Posted August 20, 2010 On older 80s and 90s cars they usually have a two-speed system with a resistor. Bypassing that can help because resistance in the system increases as the car ages. But with a PWM design there's not much of a point in completely bypassing the fuel pump module. On the search for a new DD... Link to comment Share on other sites More sharing options...
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