How about a Hobbs switch for second fuel pump

[Randy87T]

I am installing dual pumps in the tank. Can I leave pump 1 wired into the ecu with the stock wiring then use a hobbs pressure switch to turn on pump 2 (wired to battery) at 10psi ? This way I am running on only one pump with normal driving and the second pump kicking in when needed under boost. Seems like this would be a simple wire job and easy way to contol both pumps. Any thoughts ???

Better mention that I will be running E85 and trying to get to 600whp. Am heavily considering the MS3 later for the ems. I want to keep the t61 but will change it out if necessary to get 600whp. Also adding 120lb injectors (will intall today) that have been turned for easy install.

 

[Crypton2006]

What kind of fuel pumps? It seems like a good idea except it would make a nasty little spot in the tune. If u where to use a rpm activated switch the spot could be tuned out, but with a pressure switch the spike in fuel pressure will never be in the same place. I ran dual walbros for about two years and had them both running all the time. They seemed to get very loud after a hour or two drive.

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[IJ.]

This was how I used to run them way back in the late 80's, these days you can use an electronic fuel pump controller to ramp the 2nd pump in so there's no ugly transition as Crypton pointed out.

Current project car will use the stock ECU and fuel pump to feed a 2 gal surge tank that has 2x Denso Mk4 pumps and 2x Aeromotive fuel pump controllers, only other suggestion is to make sure the pumps have good non return valves or use aftermarket AN ones in the lines.

Have noticed the loud thing as well and put it down to heat soak in the fuel as running 2 pumps all the time means you're bypassing a HUGE quantity through the return line, this is why I like to boost control pump #2 and PWM pump #1 to half speed for cruise/idle.

 

[Randy87T]

Aready had a walbro and am adding another as soon as my fittings get here. Never heard of walbros getting loud. My one never did. Always a first though. I have a friend that uses the hobbs switch setup in his grand national and it seems to run great but will ask him if he has any tuning issues.

Merry Christmas to all.

 

[Randy87T]

This was how I used to run them way back in the late 80's, these days you can use an electronic fuel pump controller to ramp the 2nd pump in so there's no ugly transition as Crypton pointed out.

Current project car will use the stock ECU and fuel pump to feed a 2 gal surge tank that has 2x Denso Mk4 pumps and 2x Aeromotive fuel pump controllers, only other suggestion is to make sure the pumps have good non return valves or use aftermarket AN ones in the lines.

Is this the fuel pump controller you have ? http://www.summitracing.com/parts/AEI-16306/

That's a bit out of my league. I see some of the others going for much less... will they work ok?
Your saying that adding pump #2 only under short 1/4 mile boost conditions DOES eliminate any heat soak conditions or loud pumps as
Crypton mentioned. I saw a wiring diagram for dual pumps on 2009 thread but both pumps ran continously. Knew there had to be a better way.
Is there a time other than race conditions that someone would want both pumps running continuously?
As far as good non return valves go walbros should be just fine for now... right?





Have noticed the loud thing as well and put it down to heat soak in the fuel as running 2 pumps all the time means you're bypassing a HUGE quantity through the return line, this is why I like to boost control pump #2 and PWM pump #1 to half speed for cruise/idle.

 

[Randy87T]

Crap !! my text didn't add . lol. Will do later. gotta go.

 

[IJ.]

Yep I have 2 of those Aeromotive's, they do one that's based on boost as well but as my car is Blown and not Turbo RPM based is fine for me.

 

[Crypton2006]

I just bought a aeromotive fp controller to controlled my sx pump. I always thought they where getting loud because of what ij said, heat soak. I think running them both all the time off of the fp controller would be a simple and effective solution. Not a cheap one though. The controller will cost u more then the pumps.

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[JStoked]

Im about ready to do the dual pump mod to. So this is great info. Aromative is the best way to go? My single walboro is so loud so I can't imagine how 2 would sound.

 

[Randy87T]

Another question. What causes the fuel pump ecu to energize the relay to switch from 9v to 12v... is it rpm ?

 

[Randy87T]

What I want to do is remove the wire from pump #1 to the 12v point on the fuel pump relay. Now pump #1 will only run on 9v through the resistor which would be fine for cruise/idle.

Next parallel in two bosch relay coils ( for pumps 1 & 2 ) to that same 12v point on the fuel pump relay. The bosch relays are fused and wired to the alternator. Contacts from the bosch relays are wired to respective pumps 1 & 2. Everything grounded as necessary.

When the fuel pump ecu switches from 9v (cruise) to 12v ( in boost ) then the fuel pump relay (the 12v point) will trigger both bosch relays.

So under normal driving only pump #1 is running on 9v. Pump #2 is not operating. Under boost conditions then both pumps go to alternator volt/amps.

Hope I explained this well enough. Anyway what do you think ???

 

[te72]

Is an in-line pump an option here? That was what I was thinking about doing...

 

[Randy87T]

Is an in-line pump an option here? That was what I was thinking about doing...

I think it would work with any dual pump arrangement.

You actually understood what I was trying to say?? lol.

 

[te72]

Vaguely, I'm not very experienced or knowledgeable about wiring. My thought about the in-line pump was that it might alleviate some of the heat/noise from the gas in the tank, hopefully that makes sense?