So the big step would be to find the ecu control for this. If you can find which MUT addresses log which state the pump is in then the code to control it is only a short step away.

 

03whitegsr: I really like that approach. Depending on the pumps, you'd still want to relay home-run power to the pumps over heavier-gauge wire (think 044s, that can draw upwards of 20A at reasonable pressures). But overall, the configuration would be a lot less invasive, and the fact that we could control the cutover point in the ECU is very cool.

 

Yeah, finding the code that controls when it changes over is about all that's needed. It may even be high enough with the factory setting to work just fine as is.

I was thinking the 044s were up around 25A under high pressures, but as somebody mentioned, it's only 16-18A max. Rewiring both pumps would still be a good idea IMO.

The other thing I've been thinking about is for dual pumps in a surge tank system. I'm wondering if the factory resistor could handle a walbro 255 and a Bosch 044 pump wired in parallel. Basically a low/high system for the road race/auto-X type applications. I don't think I'll ever need dual pumps in parallel, but I do have the intention of doing a surge tank and 044 external.

 

I doubt very seriously that factory relay could handle that much current. You could use the factory relay to trigger a Bosch relay like the ones the car stereo shops use for their stuff. The relay uses about .2 amps to close either switch so... Why not piggy back onto existing high and low circuits by wiring a relay or two in parallel. If larger wiring were installed it would more than likely make up for the current used by driving the other relay(s)

http://cgi.ebay.com/ebaymotors/Bosch...22010010r12984


http://www.millionbuyplus.com/view_p...o=ACCRELAYKIT1

 

Does anybody have the part #'s on the factory relays? I use the 2g DSM fuel pump relays quite a bit and they are rated from the manufacturer at 15A constant duty. I have ran them upwards of 20A though without a problem for short periods of time (10-15 seconds).

 

I ditched that setup pretty quickly, it just didn't offer enough improvement. Buschur twin walbro kit did the trick up to 700awhp. Now I'm doing a fuel rail and going further soon.

 

What you have to keep in mind here is that the stock FPR is a rising rate unit, so for every 1psi of manifold pressure it raises fuel pressure by 1psi to overcome manifold pressure differences. So if (for example) base idle pressure is 30psi (not saying that it is, I'm not sure the exact number but I'm sure it's higher) adding an additional 20psi of boost pressure will allow an increase of 20psi of fuel pressure, netting you that 50psi rail pressure. The downfall with the fuel pump is that as pressure increases flow decreases, and thus it becomes necessary to find a way to increase flow either by an even larger pump or a twin setup to meet the demand of a fuel hungry build.

If there was a way to change values to that a second pump could turn on by means of a load % point, that would be great. But for now I'd say the Buschur type double pumper using a Hobbes switch comes in a close 2nd.

 

Bump.

I'm dealing with this idea right now. I'm on the Full-Blown setup, I've drilled the return fitting and installed an adjustable FPR but at idle with both pumps on my fuel pressure is still too high. I have the 1st pump running on the factory wiring, it runs at 9.5V at idle. The 2nd pump runs off a relay triggered by the 1st pump, it gets 14.5V at idle. This creates 55 psi of idle fuel pressure.

I just reviewed the factory wiring diagram at work with one of the EE's. We are thinking about triggering the 2nd pump with the factory ECU dual voltage setup as well. This would leave the 2nd pump off at idle and turn it on when the first pump hits 14V. The big questions is when does the ECU bump voltage from 9.5V to 14.5V? I'm going to go do some testing this weekend logging pump voltage in Logworks and see if it matches a load value. Hopefully it is high enough into the fuel demand that turning on the 2nd pump will be OK.

Right now I've got a hack I'm trying out. I have the 2nd pump running full-time through my relay, but the voltage has now been dropped to 7.5V through a large heat sinked 1 ohm resistor. My idle fuel pressure is now a livable 37 psi. I'm going to see if that's enough for 28 psi on the E85. My single modified Walbro could do it, so maybe one stock Walbro at 14 V and one at 7.5V can as well.

Stay tuned .

 

you guys are going about this in such a complicated way...hobbs switch ftw

 

Does anyone have that hobb switch part number?
After reading all this, its seems alot simpler with a hobb switch that works just fine.

Edit: I think I found it but not sure about the part number (76579)

Edit: I found the napa number and verified it. It comes with both normally close and normally open.
Tested out of the box. Normally open closes at 5-6 psi which is adjustable if needed.
Hobbs switch part number ( napa brand) 701-1591. Description- switch duel circuit.

 

Depends on the pressure you want to kick off at. Digikey list. Also, McMaster carries pressure switches as well.

 

Well, I did find all this to be too much of a hassle.

I put the Hobbs switch in that had been sitting on my desk for months. Seems to be working well.

 

Lol, it's actually very simple to trigger the second pump and only requires a single relay. It definitely doesn't need an EE to figure it out. I just want to use OEM connectors to make everything a clean install that I wouldn't have to cut any factory wiring with and finding the factory style electrical terminals is where I have the problem.

But I guess if it's too complicated for some, then don't worry about it and continue on with a Hobbs switch.

 

I'm mostly frustrated with getting both pumps to work running full-time. I tried a bunch of things to get that to work - but couldn't drop my fuel pressure at idle to where it needed to be. Adjustable FPR, drilling out the return fitting etc, it wouldn't cut it. So the hassle was mostly in the whole fueling in general - I've been throwing parts at it for a month now.

I wanted to be able to adjust the point where the 2nd pump comes on. Right now we can't do that in the ECU. So I'm using the Hobbs. If someone figures out how to adjust the trigger for the fuel pump in the ECU - I'm game.

 

Yeah, that's about the only reason I started this thread. I was hoping somebody may be able to find the trigger conditions.