FiTech fuel system install question for dual tanks

[Broncitis]

I searched a bit but did not see much in the many threads specifically about how to best handle the install with an Aux tank, WITHOUT their no return Command Center.

That thing is huge and hideous looking under the hood IMO, and I saw a guy on the street cruise at this years LEBC Roundup having fits with his which had us stopped for about an hour or more.

We have the 400 hp unit with their inline fuel pump and filter kit.

The questions I have realized as we are about to install the kit that just arrived are:

1. if the return line goes to main tank, how much fuel is bypasses in the return line (i.e. will it quickly run the aux tank dry when I switch to that by returning the fuel to the main?).

2. Pump placement: They recommend placing the pump as low as the tank and within 2 feet of it.

Obviously, it can not get mounted as low as a 23 gallon main, but I think frame mounted a foot higher will be fine as I did on my trail rig with the same type pump.

I'm wondering if I should run the aux feed line back to a Tee in front of the pre filter, or if I should use a LP carter electric pump to feed the HP mounted on the frame up in front of the switching valve? I then need to be able to switch the LP pump off when running off the aux tank. (or, is it true that diaphragm pumps can be run dry and deadheaded without damage?)

Another thought was to install the HP near the main with the return to the main, then install a LP to the aux to act as a transfer pump to refill the main when it gets low or empty.

Then there is the issue of operator error which could cause an overflow if both tanks are full and the aux is used first. I guess this could be solved by connecting both filler necks with a small line so it transfers to the lesser one rather than fills up and overflows from the gas cap.

Anyway, that was some of the various thoughts I had since I started thinking about how to proceed, what are you guys doing that are running dual tanks and avoiding the Command Center?

 

[.94 OR]

I installed an electric valve for my dual tanks. Someone makes a 6 port valve for the purpose you describe. 3 ports are 2 tanks to one line forward, the other 3 ports are 1 return line to the corresponding tanks that you are drawing off of. I don't have a part #, but that would likely be your simplest option. Then mount the HP pump between the valve and the EFI.

 

[Broncobowsher]

My last EFI with dual tanks I just let 100% return to the main 23 gallon tank. Treated it as a transfer pump. Switched back to the main tank after the fill up. You just have to pay attention not to transfer into an already full tank, they can overflow.

There was also an accumulator and a LP pump involved. I could run the aux tank empty and catch it before the accumulator went dry. Or chicken out and switch back to the main tank early and go for a little more transfer at a later time.

 

[Alpacket]

I installed an electric valve for my dual tanks. Someone makes a 6 port valve for the purpose you describe. 3 ports are 2 tanks to one line forward, the other 3 ports are 1 return line to the corresponding tanks that you are drawing off of. I don't have a part #, but that would likely be your simplest option. Then mount the HP pump between the valve and the EFI.

http://tweetys.com/index.aspx/ImageGallery/Index?productId=13836

This is what I was thinking.

 

[.94 OR]

This is what I had in mind.