Reading the quick setup guide, it says not to add additional relays to the fuel pump setup. First of all, why is this. Secondly, to safely run my dual fuel pump setup i need two fused relays controlling each fuel pump INDEPENDENTLY (as im running independent fuel for each rail).

anyone know more on this? im going to call haltech tomorrow at some point but i thought id ask here first for suggestions/clarification. thanks, heath

 

I think the idea behind what Haltech is saying is that if you add another relay you're probably adding more load and potentially pulling more load through the fuel pump circuit than what it is designed for. I'd see no reason what you couldn't run one pump directly off the Haltech circuit just as it's designed and then use a separate fused relay run directly from the battery that is switched by the fuel pump control output from the ECU. Simply gang the second relay control wire onto the existing one. This way you're not pulling any more amperage through the Haltech fuel pump circuit and the second pump will run just like the first one. It'll prime the same and shut off when the Haltech sees 0 rpm.

 

Its better to set up the relay for the pump to the secondairies on a pwm for aux fuel pump such that its not active at idle.

 

hmm maybe im not understanding.

Basically, my battery is in the trunk. I have an external 4 gang fuse block back there that gets constant power from the battery. I have two 30A fuses feeding two 30A bosch relays separately. These go to the fuel pumps independently.

Since haltech provides me a relay with a power output, can i just tie that in to the positive triggers of my independent relays? i still dont understand why they dont want me to add additional relays. another option would be eliminating their relay, extending that trigger wire, and connecting that to my two independent relays.

 

its not an aux fuel pump though.... one pump feeds the primary rail, and one feeds the secondary rail. There are two separate hard-lines from the tank to the rails.

i have it set up like that so if one pump fails it just kills one of the fuel rails instead of reducing fuel without me knowing, resulting in a blown motor. if the primary fails then the car will not idle, if the secondary fails then the car will fall on its face with lots of throttle.

 

this would work, but since i have a nice fuse block back there with the battery in the back, and virtually no resistance (and some super thick wires running to the pumps already) id rather keep it that way than to run their thin wire to the trunk and then hook up a second circuit. organizational wise... i kind of like the idea of having everything fuel related back there on it own block. it just makes it easier to keep track of and maintain. sorry im being difficult... -heath

 

As far as the motor at idle and low load is concerned it is an AUX fuel pump, setting it up as a second output allows you to eliminate significant heat which is added to the fuel under low load conditions from pumping in a circle, as well as un needed power draw of what 15 amps.

Further if either pump dies completly at high load even blowing a fuse there is still a very high likleyhood that the motor will blow, unless you have some sort of failsafe setup to monitor and react to changing pressure.

Also do you have 2 seprate FPR's?

Using a single FPR with 2 in ports and a single return channel (like most people set up a paralell system) will usually pressurize both rails with a single pump. Is like having the rails join at a Y block and then flow to a regulator. In other words if one pump does die, the other will continue to pressurize its circuit resulting in overall pressure drop.

 

good point regarding the FPR's... i only have one. i was contemplating adding check valves to each line before the FPR, though i dont know that this will solve the problem. theres not really any good way to run a dual pump system unfortunately....

ok im going to think about this a bit more. i looked through the haltech software and they have a nice aux fuel pump function. you may be right... yours might be the best solution. thanks

PS any other thoughts on a SAFE dual pump setup? ive read the numerous threads and they never come to a conclusion

 

If you have a single pump freeze under high load you are just about as likley to blow an engine. Having a second pump just conceptualy increases the chances of that fallure.

I suppose you could setup a failsafe somhow with a fuel pressure switch that would cut power to either the ign coils or injectors. But either the switch would have to refrence boost, or the FPR would not. Since the load on a haltech is boost it is possile to use a static fuel pressure providing its set high enough, the change in relative pressure with boost gets worked out in the fuel map.

 

FWIW, I blew the fuel pump fuse in my car on the dyno recently, thought something REALLY bad happened. It was winding out, about 5500 @15psi.....then BAM, just stopped.

Nothing happened to the engine though, it just shut off violently. I may have been lucky, but either way, I'd expect you could get away with it once or twice on a healthy engine before compelte destruciton.

 

how many amps was the fuse? i was planning on using a 30A fuse to give myself a good buffer (however I'll admit, i dont know the max current draw of a hard-wired pump).

-heath

 

so i was rethinking the option of adding check valves before the FPR and i believe that would eliminate the flow back problem if one pump goes out. aeromotive makes them in -6an... i know its not foolproof but maybe it would help my chances in a one pump failure situation

 

the 20AMP fuse that came with the haltech. I'm not sure adding a larger fuse would give you a very safe buffer zone. I don't know what the wiring on that circuit is rated for.......it blew my mind along with the fuse though, 20 amps dedicated to ONLY the fuel pump and it snapped - wow.

 

So then instead of reduced but constant volume and pressure throughout the fuel system, you would have a sudden wall where pressure for either primaries or secondairies would drop to zero, while the other continues functioning. I am not sure thats much of an improvment.

 

but without the check valves i would not stand a chance at all (unless i had a complex dual pump pressure monitoring system which could pull spark) as i would have no sign (other than a blown motor) that i had a failed pump/fuse/etc .

so your thought is, dont separate the primary and secondary rails correct? there seems to be no fool proof way to run a dual pump setup.

 

i called haltech, and they told me to use the power wire from their relay (he didnt think the ecu should ground *2* relays from the signal wire) and connect that to my two fuel pump relays/circuits. he also suggested adding a light/warning beeper to warn of loss of pressure

 

Your probably right, the checkvalves would probably help.

But as a real failsafe build or buy a simple cuircuit that cuts power to a solid state relay giving power to the injectors or coils or ign boxes for a pre dertimined amount of time (eg 2-3 second) in the event of pressure loss.