MIGHTYMOUSE

iTrader: (59)

Heres the deal, I have twin walbro 340's in the tank going to single -8 pressure line and billet rails blah blah; When I put everything on I just wired them both to cut on with the key like the stock one.

I have had some hissing sound through the lines which I attribute to the huge amount of fuel running through them, and more importatnly running back to the tank from the regulator.

Today I pulled each of the fuses one at a time for the heck of it and the hissing went away when only one pump is running. This was very nice because it was LOUD.

Now, I'm thinking I was probably heating the gas a bit and thats no good, so why not fix both problems... my question:

What should I use to turn on the second pump and why?
Wide open switch
Window Switch
Boost sensitive switch (hobbs?)

(i'd love some more info on where to get the the boost switch.)

The type of FI is single turbo.

I'm on the fence with all three because of the ease/cost/correctness of each way to do it.
fuel system pics

MIGHTYMOUSE

iTrader: (59)

..

xssive

iTrader: (123)

Wire it with a Hobbs switch. You can get em through summit at 5psi or you can probably find one at McMaster Carr too.

Switch

Black LS1 T/A

GWP used a Hobbs switch for my in-line pump.
Conceivably it should work for a 2nd in-tank pump.

Now, they use an Aeromotive pump controller. This keeps the normally-off in-line pump from being a restriction that drops the cruise fuel pressure down a tad.

Maybe the controller could also be better here; I've heard that just cutting the 2nd in-tank pump on and off can create priming issues for the 2nd in-tank pump. <img border="0" alt="[bang head]" title="" src="graemlins/gr_banghead.gif" />

MIGHTYMOUSE

iTrader: (59)

my fp jumps 2psi or so when the 2nd pump is cut in and out. and its on a complete separate circuit, so it doesnt prime when the first one does.. it just sits there until i get the output signal from my boost controller

SS00Blue

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MIGHTYMOUSE:
<strong> my fp jumps 2psi or so when the 2nd pump is cut in and out. and its on a complete separate circuit, so it doesnt prime when the first one does.. it just sits there until i get the output signal from my boost controller </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">OK, How's 'bout this?

Hobb's for the second pump, with an arming switch for anticipated use...

Or, how's 'bout a completely seperate SS fuel system running to a second FPR, THEN y-block just ahead of the fuel rails. Control it with the K-B Boost-a-pump (40 amp unit, of course) and an arming switch, and a throttle switch and boost controller and a... a... well, that's all I got... <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

SC-

Black LS1 T/A

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MIGHTYMOUSE:
<strong> my fp jumps 2psi or so when the 2nd pump is cut in and out. and its on a complete separate circuit, so it doesnt prime when the first one does.. it just sits there until i get the output signal from my boost controller </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I was trying to say that starting the pump from a completely off condition, I have heard, creates a lag with the additional fuel supply... possibly a priming lag? I don't know.

I was told someone tried to build their own dual in-tank with the 2nd pump coming on only under boost, and it would not work for them properly. :shrug:

MIGHTYMOUSE

iTrader: (59)

ooh.. i dunno its working good for me, though i have not pushed the limits of the 2nd pump yet.

if there is lag, ill just set the boost controller to turn on the pump sooner and sooner until it goes away i guess.