Extended capacity gas tanks: Any gripes about what's currently on the market?

[Tricky Dick]

I'm going to make a run of tanks. I have a couple prototypes designed to fit my needs, but just doing a last minute check if I'm missing any needs the market isn't currently taking care of before I do a bigger run.

Here's what I have now:

22 gallons
0.060 304 stainless
Clearance for up to 6" axle stretches
Fits no body lift or tucks higher for up to 3" body lift
2" inlet
Uses 2015 F150 fuel pump with integrated sump (10-180 ohm) or any USCAR pump of the right depth. Exploring other options.

 

[Yeller]

I’m interested in the final dimensions. Someday I’m going to do a larger tank. However my stuff isn’t normal lol.

What did you do about venting? My current tank has vents on both sides tied together to a single line. It never smells or leaks.

 

[904Bronco]

If you have the filler neck with the 5/8" return or burp line as Dad called it, They are not all on the same side of the inlet through the years...

 

[Madgyver]

we had to do this...

 

[Tricky Dick]

I’m interested in the final dimensions. Someday I’m going to do a larger tank. However my stuff isn’t normal lol.

What did you do about venting? My current tank has vents on both sides tied together to a single line. It never smells or leaks.

Overall rough dimensions are 20.5 x 13.5 x 22.5, the side profile is this shape. The current revision only has a single burp vent next to the filler.

If you have the filler neck with the 5/8" return or burp line as Dad called it, They are not all on the same side of the inlet through the years...

Is the hose flexible enough to cross over if there was only a single?

we had to do this...

And this is why I decided to put one out that's ready to run. Nobody is catering to the stretch crowd. I was looking at dropping a grand+ on a tank then still having to modify it.

 

[Yeller]

@Tricky Dick thanks! I need to do some measuring….

 

[ntsqd]

Does your capacity estimate include some expansion volume? I ask because I've been pondering building a tank for Snowball to push it up to a ~400 main tank range, and this is a concern. OEM tanks feature it, but I've not been able to find any suggestions or formula(s) for how much this volume should be. Some OEM tanks appear to have a huge expansion volume while others are maybe 5%-7% of the total.

 

[Tricky Dick]

Does your capacity estimate include some expansion volume? I ask because I've been pondering building a tank for Snowball to push it up to a ~400 main tank range, and this is a concern. OEM tanks feature it, but I've not been able to find any suggestions or formula(s) for how much this volume should be. Some OEM tanks appear to have a huge expansion volume while others are maybe 5%-7% of the total.

That calc is gross volume.

Always take AI with a huge grain of salt, but it's saying 2%. I would guess there would be some air space above the burp vent?

 

[ntsqd]

When I calc the actual volume of the tank in the FSB it comes out something like 42 gallons, BUT that isn't taking into account that it has rounded corners. (I should model it sometime and see what SW says the volume is.) Anyway, the FSB tanks are listed as a 33 gallon tank and the most that I've ever put in it was 32 gallons. Tanks in other vehicles that I've owned had their practical capacity much closer to the calculated capacity. Makes me think that maybe the OEM's don't know, but that seems highly unlikely.

Bechtold doesn't list volumetric expansion coefficients in his Alt. Fuels Guidebook, so I went looking for it. Engineer's Toolbox lists it: https://www.engineeringtoolbox.com/cubical-expansion-coefficients-d_1262.html When I work the formula I don't get a result that matches what I've casually observed. The calculated increase in 20 gallons going from 65°F to 100°F is .665 gallon. Maybe some tanks have large expansion volumes to keep them from pressurizing excessively?

 

[Tricky Dick]

When I calc the actual volume of the tank in the FSB it comes out something like 42 gallons, BUT that isn't taking into account that it has rounded corners. (I should model it sometime and see what SW says the volume is.) Anyway, the FSB tanks are listed as a 33 gallon tank and the most that I've ever put in it was 32 gallons. Tanks in other vehicles that I've owned had their practical capacity much closer to the calculated capacity. Makes me think that maybe the OEM's don't know, but that seems highly unlikely.

Bechtold doesn't list volumetric expansion coefficients in his Alt. Fuels Guidebook, so I went looking for it. Engineer's Toolbox lists it: https://www.engineeringtoolbox.com/cubical-expansion-coefficients-d_1262.html When I work the formula I don't get a result that matches what I've casually observed. The calculated increase in 20 gallons going from 65°F to 100°F is .665 gallon. Maybe some tanks have large expansion volumes to keep them from pressurizing excessively?

Being that mine has hard corners it's pretty easy to calc. My CAD program tells me the area of the side plate, multiply that by the width, divide by 231.

I think in practice you burn off enough after leaving the station that expansion never much of an issue.

 

[ntsqd]

I've been on trail runs where the fuel got hot enough to gurgle out of the filler, not just a trickle. Sometimes it was partially because the vehicle was side-hilled, but not always.

No notch or pocket for the fuel pump?

 

[Tricky Dick]

I've been on trail runs where the fuel got hot enough to gurgle out of the filler, not just a trickle. Sometimes it was partially because the vehicle was side-hilled, but not always.

No notch or pocket for the fuel pump?

There is a notch, the pump sits 2" below the top of the tank.

 

[Tricky Dick]

The F150 pump isn't set in stone either, any USCAR pump will fit. The F150 pump is 10-180 ohm, I'm trying to find one that does 10-70. 2008 ish GM looks like 40-250 which should work with my Intellitronix cluster, but I want a solution for guys with stock range fuel gauges.

 

[Tricky Dick]

Here's how the F150 pump is set up. Don't even need a burp vent on the tank if you use one of these, it's built into the pump.

 

[ntsqd]

Not sure that I understand what is meant by "burp vent". As I understand them a fuel tank has two vents, one that exits out the fill neck when the tank is being filled, and the other is the service vent that 'breathes' thru the charcoal canister (in late models anyway) for air that replaces the consumed fuel.

I see that that fill neck has a 'normal' vent in it. My FSB's fill neck is coaxial where there is a hose down the middle of the filler assembly that the fuel flows thru, and it vents around the outside of that hose. It's a PITA to R&R, only partly due to the routing.
It seems like the location (elevation above the tank bottom) of the vent tends to determine how actually full the tank can get before the fill nozzle shuts off. That's my working theory anyway, I'm not convinced of it yet. It makes sense that if air is trapped above the vent that fuel won't be able to get there unless the tank is pressurized.

 

[Tricky Dick]

Not sure that I understand what is meant by "burp vent"

Filler neck vent.

 

[Tricky Dick]

 

[stout22]

Looking forward to seeing it mounted and see how well it tucks up under a bronco.

 

[Tricky Dick]

Looking forward to seeing it mounted and see how well it tucks up under a bronco.

I'm going to do a video on it.

Pivoting back to stainless after learning about how ethanol reacts with aluminum. It adds about $150 per tank unfortunately.

 

[hyghlndr]

Need to have drain plug, biggest issue is what was $400-500 is now $1000+.