Fuel Return Line on Bottom of Tank?

[wesinls]

I've always had all my return lines (for an FI system) on top of a tank - but curious if anyone has seen issues with adding it on the bottom? For a honda car I plan to use a spun aluminum tank and add a sump (pic below) - use one for supply and one for return, just never had a return on the bottom of a tank.

 

[Looney Duner]

My last 2 cars were that way. No issues

 

[Stinky]

Theoretically, as explained by my freshman math teacher, at "Taco-Tech," (AWC) it takes less effort to make it flow that way.

If it flows into the top,
you have to lift a column of gas the size of the line HIGHER THAN the TOP OF THE TANK
as the line goes above the top of the tank.

If it flows to the bottom, it takes less pressure as
you have to lift a column of gas the size of the line only to the TOP OF THE GAS LEVEL
(which is below the the top of the tank....duh). When full, this is gonna be w/in a few inches of being the same place. But, if your gas level is down 6 inches to a foot, from full, then you will have to raise the gas 6 inches to a foot less than the top of the tank (or actually 7-13" less than the top, assuming that you fill your tank to the top, and that your lines go 1" above that).

 

[Kat-A-Tonic]

Theoretically, as explained by my freshman math teacher, at "Taco-Tech," (AWC) it takes less effort to make it flow that way.

If it flows into the top,
you have to lift a column of gas the size of the line HIGHER THAN the TOP OF THE TANK
as the line goes above the top of the tank.

If it flows to the bottom, it takes less pressure as
you have to lift a column of gas the size of the line only to the TOP OF THE GAS LEVEL
(which is below the the top of the tank....duh). When full, this is gonna be w/in a few inches of being the same place. But, if your gas level is down 6 inches to a foot, from full, then you will have to raise the gas 6 inches to a foot less than the top of the tank (or actually 7-13" less than the top, assuming that you fill your tank to the top, and that your lines go 1" above that).

What you said is all true, but you are neglecting the exit losses of a submerged fitting vs free flowing into air.

 

[AlpineFunco]

My return is right next to my output. No problems.

 

[ChasingSand]

My Return is smack in the middle of my tank.

 

[Jtmoney714]

Only knock would be that you are heating up the fuel. As you are cycling the same fuel over and over again. But I doubt it’s an issue.

 

[Mac]

My fuel return is on the bottom and has no issues.

 

[punkur67]

Mine returns to the sump too. Never had an issue