Factory ECU Dual Pump Control
Apr 16, 2009, 10:44 AM
#1
Factory ECU Dual Pump Control
It seems like it should be fairly straight forward to control twin pumps with the factory ECU and a little rewiring. Has anybody tried this?
Below is the wiring diagram for what is supposed to be the 2003 EVO. The pin diagram appears to be for a 3 plug ECU, but I would imagine the 4 Plug ECU based car is wired very similarly. I have annotated what the corresponding pin is likely to be in the EVO 8.
It looks like Fuel Pump Relay 3 is a normally closed relay. Which makes sense as in stock form you would want the car to run the pump with full voltage if the relay did fail to function. I would assume there is a table or value in the ECU related to when the ECU energizes/deenergizes fuel pump relay 3. Because it is normally closed, this makes it pretty simple to set everything up and maintain the same control scheme.
As far as rewiring, I think it might be best to just scrap much of the factory wiring as this way, you can rewire the supply line with a large main power wire. Here is how I am thinking, but there is probably a better way.
The only real concern I see is under certain conditions, the factory ECU may try to turn the fuel pump to full power when you may not expect it. Possibly low battery voltage, cold start, emission related, etc. It would be nice if something as simple a LOAD < XXX and pin 39 breaks the ground.
Below is the wiring diagram for what is supposed to be the 2003 EVO. The pin diagram appears to be for a 3 plug ECU, but I would imagine the 4 Plug ECU based car is wired very similarly. I have annotated what the corresponding pin is likely to be in the EVO 8.
It looks like Fuel Pump Relay 3 is a normally closed relay. Which makes sense as in stock form you would want the car to run the pump with full voltage if the relay did fail to function. I would assume there is a table or value in the ECU related to when the ECU energizes/deenergizes fuel pump relay 3. Because it is normally closed, this makes it pretty simple to set everything up and maintain the same control scheme.
As far as rewiring, I think it might be best to just scrap much of the factory wiring as this way, you can rewire the supply line with a large main power wire. Here is how I am thinking, but there is probably a better way.
The only real concern I see is under certain conditions, the factory ECU may try to turn the fuel pump to full power when you may not expect it. Possibly low battery voltage, cold start, emission related, etc. It would be nice if something as simple a LOAD < XXX and pin 39 breaks the ground.
Last edited by 03whitegsr; Apr 16, 2009 at 04:19 PM.
Apr 16, 2009, 11:52 AM
#2
Just FYI, RRE wrote up a quick blurb on the stock dual-circuit configuration a few years ago, drawing on the FSM:
http://www.roadraceengineering.com/e...elpumpinfo.htm
I don't see any reason why that configuration couldn't be adapted to kicking on a second pump under load, rather than drawing voltage down on the first pump at idle. You'll almost certainly need an AFPR to overcome the return overrun at idle, but anyone running dual pumps is already at that point anyway.
http://www.roadraceengineering.com/e...elpumpinfo.htm
I don't see any reason why that configuration couldn't be adapted to kicking on a second pump under load, rather than drawing voltage down on the first pump at idle. You'll almost certainly need an AFPR to overcome the return overrun at idle, but anyone running dual pumps is already at that point anyway.
Apr 16, 2009, 01:27 PM
#4
I think the only thing you have wrong is that you would want to find what controls the output to pin 55, not 36. I would think that 55 is what controls the hi/low load operation since the resistor jumps around that relay. You would then need to jump into that line before the relay so that you had control, rather than on the output where you would still get signal from the resistor.
Apr 16, 2009, 04:28 PM
#5
I think the only thing you have wrong is that you would want to find what controls the output to pin 55, not 36. I would think that 55 is what controls the hi/low load operation since the resistor jumps around that relay. You would then need to jump into that line before the relay so that you had control, rather than on the output where you would still get signal from the resistor.
I'm suggesting eliminating that entire line and going straight from the battery with large gauge wire to a primary relay and then secondary relay. You would run a new line from the ECU pin to the new relay. No factory wire involved at all.
What I'm after is what are the conditions that control pin 39/pin 55 in the ECU and are they programmable? Other than that, I am 99% sure it will work. I think it is a far better solution than using a Hobbs pressure switch like the kits on the market use. Just like how the AEM takes care of business.
Apr 16, 2009, 07:30 PM
#6
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You got my attention try it and give us some feedback. I have a 255 in my car now and another sitting on the shelf just waiting to get brave enough to figure out how to put it in
Apr 16, 2009, 10:39 PM
#7
Pin 39 is the right pin for the 4 plug EVOs and what I meant to put in there, you'll see the diagram is correct. Pin 55 is (likely) the same output on the 3 plug ECUs.
I'm suggesting eliminating that entire line and going straight from the battery with large gauge wire to a primary relay and then secondary relay. You would run a new line from the ECU pin to the new relay. No factory wire involved at all.
What I'm after is what are the conditions that control pin 39/pin 55 in the ECU and are they programmable? Other than that, I am 99% sure it will work. I think it is a far better solution than using a Hobbs pressure switch like the kits on the market use. Just like how the AEM takes care of business.
I'm suggesting eliminating that entire line and going straight from the battery with large gauge wire to a primary relay and then secondary relay. You would run a new line from the ECU pin to the new relay. No factory wire involved at all.
What I'm after is what are the conditions that control pin 39/pin 55 in the ECU and are they programmable? Other than that, I am 99% sure it will work. I think it is a far better solution than using a Hobbs pressure switch like the kits on the market use. Just like how the AEM takes care of business.
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Apr 16, 2009, 10:48 PM
#8
I don't think you understand what I'm saying here. Having the resistor will not help you on a dual pump setup. You also need larger wire to run two pumps, as two Bosch 044s will pull almost 50 amps under full load, if I recall correctly.
I'd also rather not hack up the factory harness when all I would have to do on this method is de-pin the ECU on two pins and pull a fuse in the fuse box then wire everything else up without touching the factory wiring.
I'd also rather not hack up the factory harness when all I would have to do on this method is de-pin the ECU on two pins and pull a fuse in the fuse box then wire everything else up without touching the factory wiring.
Apr 17, 2009, 08:26 AM
#9
I don't think you understand what I'm saying here. Having the resistor will not help you on a dual pump setup. You also need larger wire to run two pumps, as two Bosch 044s will pull almost 50 amps under full load, if I recall correctly.
I'd also rather not hack up the factory harness when all I would have to do on this method is de-pin the ECU on two pins and pull a fuse in the fuse box then wire everything else up without touching the factory wiring.
I'd also rather not hack up the factory harness when all I would have to do on this method is de-pin the ECU on two pins and pull a fuse in the fuse box then wire everything else up without touching the factory wiring.
I'm thinking buschur / full blown setup rather than 044's. Either way it looks like the 044 is only rated @ 13amps / pump at crack pressure and the Walbro 255 is rated at 15.8 amp / pump at crack pressure. Thats still alot of current for the tiny OEM wires.
In any case, if you could find the resistance value then you could probably mirror the stock setup pretty easily. I also agree that a beefier wire and separate setup would be better, but alot of people would rather use what is already there.
Heck, I need to rewire my single walbro sometime anyway...
Last edited by fostytou; Apr 17, 2009 at 08:58 AM.
Apr 17, 2009, 08:55 AM
#10
Ooooo look what I found. This is interesting. I had heard about the boost-a-pump, but hadn't seen flow tests. It looks like @ 16.5v a single Walbro 255 with 30psi of boost should be able to support my 1200cc injectors still... (roughly 1105cc * 4 ~= 736*6 in the chart)
http://www.stealth316.com/images/flowtest-walbro.gif
Not sure how much the pump would be loving life at that voltage though.
http://www.stealth316.com/images/flowtest-walbro.gif
Not sure how much the pump would be loving life at that voltage though.
Last edited by fostytou; Apr 17, 2009 at 08:59 AM.
Apr 17, 2009, 09:17 AM
#11
Boost-a-pump i believe was used by mellon before he upgraded to the br double pumper. im not sure what injectors and hp levels he got while using that.
i guess the biggest problem of using this is that it would probably make the walbro overheat. probably not an issue if the fuel in the tank is above half but would probably be an issue if the fuel is below 1/4 tank.
i guess the biggest problem of using this is that it would probably make the walbro overheat. probably not an issue if the fuel in the tank is above half but would probably be an issue if the fuel is below 1/4 tank.
Apr 17, 2009, 12:02 PM
#13
If they're plumbed in series, it doesn't matter.
If they're plumbed in parallel (like a lot of aftermarket dual-intank setups), your pumps should have an integral check valve, or you should add one to the system. Ensuring each pump is protected by a check valve (integral or external) is good practice even if you don't actuate them individually, to protect the pumps from cavitation.
If they're plumbed in parallel (like a lot of aftermarket dual-intank setups), your pumps should have an integral check valve, or you should add one to the system. Ensuring each pump is protected by a check valve (integral or external) is good practice even if you don't actuate them individually, to protect the pumps from cavitation.
Apr 17, 2009, 06:47 PM
#14
Ooooo look what I found. This is interesting. I had heard about the boost-a-pump, but hadn't seen flow tests. It looks like @ 16.5v a single Walbro 255 with 30psi of boost should be able to support my 1200cc injectors still... (roughly 1105cc * 4 ~= 736*6 in the chart)
http://www.stealth316.com/images/flowtest-walbro.gif
Not sure how much the pump would be loving life at that voltage though.
http://www.stealth316.com/images/flowtest-walbro.gif
Not sure how much the pump would be loving life at that voltage though.
http://www.msdfuelinjection.com/efi_fuelpump.html
Increasing rail pressure will help your 1200's as well. Go to RC engineerings website and you will discover most 1200's on the market only flow 1200cc with over 50 psi rail pressure and only flow around 1070cc with our 43.5 psi.
PS I have 1200 cc injectors also
Apr 17, 2009, 09:25 PM
#15
You know, there is definitely a more simple solution.
Simply running a wire from before the fuel pump resistor (wire marked as 2R in diagram in first post) to the high side of a normally closed relay and then the low side to pin 39 (pin 55 on 3 plug ECUs) would provide basically the "perfect" switch setup. Basically like duplicating the Relay 3 setup but without the resistor.
This would allow Pump 1 to operate at a low voltage at low load, then under high load, it would switch pump 1 to full voltage as well as turn on pump 2.
Simply running a wire from before the fuel pump resistor (wire marked as 2R in diagram in first post) to the high side of a normally closed relay and then the low side to pin 39 (pin 55 on 3 plug ECUs) would provide basically the "perfect" switch setup. Basically like duplicating the Relay 3 setup but without the resistor.
This would allow Pump 1 to operate at a low voltage at low load, then under high load, it would switch pump 1 to full voltage as well as turn on pump 2.
Last edited by 03whitegsr; Apr 17, 2009 at 09:27 PM.