Dual Tanks and Fuel Surge Tanks

rusty_408

rusty_408

Rusty
I Support the NLOC
I got this idea from StruckBy and wanted to share. I think it was on FB someone showed a KB build with a single surge tank. I liked it, but it would take a long time to displace the fuel in one FST when switching tanks. I came up with this idea of two FSTRs to minimize the time it would take to swtich. Has the added benefit of keeping the in-tank pumps stock and no need to sump it or go with an aftermarket hat. Easy to change pump with the FST being accessible. I've done a lot of math on this setup and feel pretty confident. I'm running the lower arrangement with just the rear. I'll setup the E-85 later.

I showed @Blue Oval Forever last time he came over. Thoughts? And problems you can think of that I'm not foreseeing?
 

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Installed pic


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I run a single surge on my 94 with the stock in tank pumps - the install and lessons learned is in my build thread. It wouldn't take long to purge one fuel and change to the other. With a proper flex fuel tune and sensor, you'd be fine with one surge tank.

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FMOS Racing said:
I run a single surge on my 94 with the stock in tank pumps - the install and lessons learned is in my build thread. It wouldn't take long to purge one fuel and change to the other. With a proper flex fuel tune and sensor, you'd be fine with one surge tank.

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that's a good point. I probably could use the one FSTR and rely on the intank factory check valves. I have bad experiences with those failing though. I drew this sketch thinking i wouldn't use a flex fuel sensor.
 
rusty_408 said:
that's a good point. I probably could use the one FSTR and rely on the intank factory check valves. I have bad experiences with those failing though. I drew this sketch thinking i wouldn't use a flex fuel sensor.
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Even if you have dedicated E85 supply system you should run a flex fuel sensor, unless you're going to only use drum E85. But even then you'd want to test every tank.

Believe me, pump E85 varies a LOT.
 
Raymond_B said:
Even if you have dedicated E85 supply system you should run a flex fuel sensor, unless you're going to only use drum E85. But even then you'd want to test every tank.

Believe me, pump E85 varies a LOT.
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I actually was planning to use drum e85. I won't use much fuel because I plan to spend most of my time on 93. That was the beauty of the two onboard fuels.

I'm still on a Quarterhorse setup so for now, so flex fuel sensor is out for the time being. Planning to go Holly Term X one day, maybe I'll do it when I go E85 and keep the one FST.
 
rusty_408 said:
I actually was planning to use drum e85. I won't use much fuel because I plan to spend most of my time on 93. That was the beauty of the two onboard fuels.

I'm still on a Quarterhorse setup so for now, so flex fuel sensor is out for the time being. Planning to go Holly Term X one day, maybe I'll do it when I go E85 and keep the one FST.
Click to expand...
You still got Decipha tuning your truck?

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One thing I learned was that the shuttle valves require about 10 psi line pressure to work properly, so I actually have a cheap regulator in the surge tank return to the oem system to hold some pressure in the loop.

With yours, you could probably put it in the supply side, but on mine it quieted the surge tank pump dramatically to have a little pressure on it.

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rusty_408 said:
Yup! He's waiting on me right now.


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Interested to see how quick you go on track with stock ECU. I chased my tail a little bit trying to do that but Decipha probably has some tricks up his sleeve. Best tuner I know.

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FMOS Racing said:
One thing I learned was that the shuttle valves require about 10 psi line pressure to work properly, so I actually have a cheap regulator in the surge tank return to the oem system to hold some pressure in the loop.

With yours, you could probably put it in the supply side, but on mine it quieted the surge tank pump dramatically to have a little pressure on it.

Sent from my motorola edge plus 5G UW (2022) using Tapatalk
Click to expand...
What do you think about just running something like this on the supply side to hold some back pressure? It has a gauge port so i can measure the back pressure. I'll have to drill it out a little larger, but seem simpler than running a regulator.

www.vaporworx.com

AN6 Male-Male 0.041" Restrictor Fitting w/ 1/8" - NPT On Side - VaporWorx

AN6 M/M restrictor fitting. 1LPM @ 42psi gasoline. Gauge port sensor fitting. 1/8" - NPT female thread on the hex side. Black hardcoat anodized.
www.vaporworx.com www.vaporworx.com
 
Just to put my 2 cents. I've been running mine unrestricted for 4 years about 10k miles problem free. so although a restrictor or regulator will prevent the pulsing I'm not sure its actually needed. Restrictor does seem like the simplest solution tho so I may look into that aswell.
 
FlatOut said:
Just to put my 2 cents. I've been running mine unrestricted for 4 years about 10k miles problem free. so although a restrictor or regulator will prevent the pulsing I'm not sure its actually needed. Restrictor does seem like the simplest solution tho so I may look into that aswell.
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do you run both tanks? I was thinking that @FMOS Racing was talking about needing the back pressure it to trigger the shuttle valves to prevent crossflow. I do agree and i dont think i care too much about pulsing.
 
I can't speak to any other options. Once I had mine set and was happy with the operation, I removed the gauge and haven't thought about it further. ~5K miles on the setup so far.

It worked fine without the regulator, just had the continuous, very audible ~2 Hz pulse where the pump sound changes and you can hear the shuttle valve pop. A "pank pank pank pank" kind of sound. $30 of regulator and fittings was necessary for my sanity. :D
 
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