[PhullD]

In order:

I know the Long Ranger kit is for a Frontier. At the time I wasn't sure if it could be made to work with the Xterra. @idn88 confirmed this so ya that is a no go it looks like for anyone wanting a compete kit.

While you have a good thing started, I am concerned about one thing. The frame flexes a bit offroad. By tying the tank to that cross-member and into the spare brace (the tank being the connection between those two sides), won't it flex at two different locations and warp the tank? Just something to think about. It might not, but maybe something worth testing.

As for over-filling the OEM tank and the gas going into the evap lines, I don't think that is a problem. The plan right now is a tie-in line to the OEM filler neck near the OEM tank, so worst case you'd just fill the aux. tank line coming from the aux. tank fuel pump. The fuel pump only flows one way so you'd fill up that line pretty fast. It should continue to fill up normally afterwards.

The aux. tank should fill up normally as well as the filler neck will be isolated. It will be as though the tank is in a Chevy Blazer. Hoping to have the filler neck on the rear plastic quarter panel or the rear bumper. As long as pressure is maintained I think you can also tie-in to the evap system with the aux. tank vent line. Still working out the details, but this is a slow going project.

The gas tank that we've settled on seems to be the 2002 Chevy Blazer tank (19 gal). Here are some test fitting pictures. Keep in mind the spare tire brace has not been modified yet, just testing to see if the tank fits.

There is also a chance we make a few kits afterwards with the pre-fabed brackets/skid but haven't discussed this at length yet.

I'll update when I know more!

 

[Nasarno]

Gas tank is not tightened to The front bracket (welded on crossbar tube), it just sits on it. So, it can move in that point. But the two side brackets are were your point applies to. I'll discuss it with the welder friend to see how flexible is the aluminum tank he built. Worst case is, we can modify the brackets and open the room for rubber mounts to handle the stress.


About the tank you found, what a nice find!! That's cheap also and fits so good. It won't fit my car though, I have a small air tank of the OBA and the water pump and hoses of onboard water system right behind the bumper.


Talking about overfilling the main tank, I asked because the bottom of my tank sits almost in the same height of the input port on main tank. So, I'm thinking of a gravity feed solution, trying to avoid the pump.


My initial plan was to put this aux tank in the middle of filler pipe/hose. In other words, the filling neck connects to the input port of the aux tank and drain port of it goes directly to main tank. The vent line will be split to a Y connection, so both tanks' air vent will join to the same pipe that goes up to the filler neck. But I'm afraid using this way, I'll defeat the designated mechanism that protects the main tank from overfilling.


The welder friend recommended me to make a dual filler neck joined just below the cap (similar to the LongRanger ) from day first, but I insist on simpler less intrusive solution, if there is any.

 

[ChrisHaynesUSA]

armor considerations?

heat from exhaust considerations?

 

[PhullD]

Talking about overfilling the main tank, I asked because the bottom of my tank sits almost in the same height of the input port on main tank. So, I'm thinking of a gravity feed solution, trying to avoid the pump.

My initial plan was to put this aux tank in the middle of filler pipe/hose. In other words, the filling neck connects to the input port of the aux tank and drain port of it goes directly to main tank. The vent line will be split to a Y connection, so both tanks' air vent will join to the same pipe that goes up to the filler neck. But I'm afraid using this way, I'll defeat the designated mechanism that protects the main tank from overfilling.


The welder friend recommended me to make a dual filler neck joined just below the cap (similar to the LongRanger ) from day first, but I insist on simpler less intrusive solution, if there is any.

I looked into the gravity feed. I couldn't find a tank that would be oriented in such a way to make it work. Then, every forum I looked at said it was more trouble than it is worth. I can't remember the exact reasons, but it was either that it was slow to feed and drain unless it was situated above the main tank (plus the evap stuff), or that there was a desire to isolate the systems. If you have a tank that can make it work, it would be like running one big OEM tank I guess when connected. You could have a valve on a switch to initiate the feed and still isolate them if you wanted to, but you'd need them to fill separately.

 

[PhullD]

armor considerations?

heat from exhaust considerations?

Definitely planning on a steel skid. An exhaust shield would be easy to do around the exhaust, but it has a decent amount of space from the tank. I don't have the exact numbers on me right now. Can also slightly bend the exhaust out a bit.

 

[Nasarno]

I looked into the gravity feed. I couldn't find a tank that would be oriented in such a way to make it work. Then, every forum I looked at said it was more trouble than it is worth. I can't remember the exact reasons, but it was either that it was slow to feed and drain unless it was situated above the main tank (plus the evap stuff), or that there was a desire to isolate the systems. If you have a tank that can make it work, it would be like running one big OEM tank I guess when connected. You could have a valve on a switch to initiate the feed and still isolate them if you wanted to, but you'd need them to fill separately.

Isolating the feed line from aux to main tank using a electric valve is exactly my plan B. Using a pump is the last solution, plan C.

 

[ChrisHaynesUSA]

I too have been thinking a long time about an aux tank.
what I am currently looking at is a custom tank mounted on the roof for extended expedition off-roading.

I think the rear of my Gobi is a good place and a gravity feed to the regular tank is easily done.

I currently can put 6 NATO jerrycans across the rear area of the Gobi.
which means to me that I need to have a custom fab tank that can hold 30-35 gallons of fuel up there.

Been looking at a company in Florida to fab the tank and Arabias overkill has used them for years..

https://www.boydwelding.com/

 

[AdventureRider81]

I too have been thinking a long time about an aux tank.

what I am currently looking at is a custom tank mounted on the roof for extended expedition off-roading.



I think the rear of my Gobi is a good place and a gravity feed to the regular tank is easily done.



I currently can put 6 NATO jerrycans across the rear area of the Gobi.

which means to me that I need to have a custom fab tank that can hold 30-35 gallons of fuel up there.



Been looking at a company in Florida to fab the tank and Arabias overkill has used them for years..



https://www.boydwelding.com/

Nice find, thank you all for sharing! Sub'd.

Sent from my SM-G950U using Tapatalk

 

[PhullD]

I too have been thinking a long time about an aux tank.
what I am currently looking at is a custom tank mounted on the roof for extended expedition off-roading.

I think the rear of my Gobi is a good place and a gravity feed to the regular tank is easily done.

I currently can put 6 NATO jerrycans across the rear area of the Gobi.
which means to me that I need to have a custom fab tank that can hold 30-35 gallons of fuel up there.

Been looking at a company in Florida to fab the tank and Arabias overkill has used them for years..

https://www.boydwelding.com/

Are you going to run the lines along the back side of the vehicle? I’m sure going through the roof and into the cab would not be the safest idea. If that’s your plan to have a tank up top, you might as well just have a hose you can pull out to feed the stock tank filler when needed and save all the complications of the plumbing. When I worked in the bush plenty of pickups had a seoarate fill-up tank in the back they could re-fill the main tank with. You still have to fill up the main tank manually but no big deal.

How would you fill that tank up there?

 

[ChrisHaynesUSA]

I would have a standard tank cap up there and climb to the rear ladder when filling.
when using to fill the main tank have a hose coming from a shutoff (lockable) valve.
Gravity fill.

 

[Nasarno]

As I mentioned earlier, the bottom of my AUX tank is level or slightly upper than the main tank's filler port. So, I'm trying to find a gravity feed solution. I always prefer the most stealth and less intrusive approach.


Therefore, my early plan was simply place the aux tank at the middle of filler pipe/hose and connect the filler vent line of both tanks to the same line using a T connection. There are some concerns for this approach, though. To understand it, first I need to know the main tank behavior and features.


Following picture shows the main tank during filling, to the best of my knowledge. Gas station nozzles have an embedded air-suction pipe inside the nozzle and it shuts off the valve if cannot freely suck the air. When tank is not filled up to filling vent port, the air inside the tank is sucked in freely and filling continues.



When gas comes up to the height of the filling vent port, it takes more power to suck in the liquid fuel through the vent pipe. That triggers the filler valve stopper in the nozzle.


The filling vent port is located lower than tank's top in order to keep a gap on top of the tank. One reason is to keep room for the liquid expansion in higher temp. The other reason seems to keep the sensors and other equipment which are placed on the top of the tank from being drowned in fuel. Some articles I found say if the tank is filled to the top, gas may enter the evap line and ultimately fill the canister with liquid that kills the charcoal. Some other articles say there is a liquid/vapor separator that prevents fuel from entering the evap line; I couldn't verify if that exists on Xterra tank or not, and in that case, what other potential damage may happen if the tank is filled to the top.


There is another ambiguity about the evap control system. Almost all articles say the fuel tank and evap control system of modern cars is designed to seal the gas and its vapors from ambient air, because gasoline vapor is big source of emission. The same articles then say the evap vent valve is normally open! FYI, evap vent path provides the air for the tank when engine is running and fuel is pumped out from the tank. All other ports are connected to a sealed end except the evap vent line that breathes in the air to replace the empty space of tank. Evap vent valve is only closed during the test of evap system per all available articles.

But then if the valve is normally open (while the engine is off and car is parked for days), doesn't it leak the gas vapor to ambient? doesn't it defeat the whole purpose of evap control system?!


If evap vent valve is normally open and can leak the air out, then I cannot use my initial plan:



The main tank will be ultimately filled to the top and if the liquid/vapor separator does not exist or exists but cannot hold the pressure of the gas from higher mounted aux tank, gas will leak into evap line which is a disaster.


So, I had to change my plane to a safe one.

 

[Nasarno]

I modified the initial plan by adding solenoid valves to both aux tank vent line (before the T-connection) and drain line (connected to main tank's filler). A 1" normally closed valve for drain/filler pipe, and a 1/4" normally closed valve for vent line. Both valves are driven by the same control switch.


Switch is OFF normally, so valves are in their normal position. Switch shall be ON during filling main tank. This setup allows the nozzle stopper work as intended and it will shut off the filler when main tank is full.



Then switch shall be turned OFF to fill the aux tank, using the same filler neck. Again, it will let the nozzle stopper do its job, this time for the aux tank.



Finally, when the main tank is running low, turning the switch ON lets the gas transfer from aux to main tank. Just need to watch it and turn OFF the switch once transfer completed.



I think this is a safe method and keeps all the systems and protections working, while it's easy to use and pretty much hidden.


Please let me know if you see any problem or point of concern on this plan.

 

[PhullD]

I had this discussion last week with the shop that's helping me with this. It's quite the conundrum isn't it? They came up with the following to remove the evap system from the equation. The tanks will be filled at the same time essentially but they must be more equally leveled. If this can't be maintained with where I want the auxiliary tank then I'll have to abandon the idea (see bottom of post) and opt for a slightly more costly method of separate systems. Anyway plan A is as follows:

The auxiliary tank will be tied into the filler neck in two places. One point below to fill the auxiliary tank, and one above where the fuel from the auxiliary tank fuel pump comes in. If the OEM tank is full the fuel just recirculates. The OEM vent line will be tapped also by the auxiliary tank. When the OEM tank is filling-up you automatically begin fueling up the auxiliary tank. The fuel nozzle at the station should still work the same when the threshold is reached just like OEM. This is about the same exact system as some of the Chevy trucks with dual tanks employed.

However, if the tanks can't be filled at the same time, plan B is to make the tanks two separate systems with two separate filler necks. This negates all issues of the evap system but requires an extra filler neck and needs a provision to recirculate the fuel if the pump is accidentally turned on and the OEM tank is full. The fuel pump from the Blazer should have a return line, I suppose that can be tied in above where the fuel sending line is.

Next thing we are working on is power to the auxiliary fuel pump. If it goes on with the OEM systems it will run dry when the auxiliary tank empties. You can have a master switch to turn it on in the cab, but what if you forget to turn it off?

This is where we are at right now. What I am thinking is since the fuel level sends a signal in ohms to the fuel gauge from 0-90 ohms, perhaps you can get an auto-shutoff worked out for the fuel pump. I'd rather not be reliant on a manual switch in the cab for the power in case someone leaves it on by accident on a long trip (and by that I mean me).

 

[Nasarno]

Next thing we are working on is power to the auxiliary fuel pump. If it goes on with the OEM systems it will run dry when the auxiliary tank empties. You can have a master switch to turn it on in the cab, but what if you forget to turn it off?

This is where we are at right now. What I am thinking is since the fuel level sends a signal in ohms to the fuel gauge from 0-90 ohms, perhaps you can get an auto-shutoff worked out for the fuel pump. I'd rather not be reliant on a manual switch in the cab for the power in case someone leaves it on by accident on a long trip (and by that I mean me).

I'm afraid your plan A suffers from the same issue of my initial plan; risk of overfilling the OEM tank. When both tanks are directly connected and are filled together, filling continues till the fuel level passes the highest threshold level of the two, in this case it's the vent port of the AUX tank. If that is located higher than top of the OEM tank, you overfill it and get to the unknown zone of: does it damage the sensors? does it enter the evap pipe? and so on...


So, you shall either keep the AUX tank's threshold level lower than top of OEM tank, or fill them separately.


You can absolutely use the sending unit's variable resistor to detect the border condition and turn off your pump safely. It just needs a little bit of R&D, which is fine. What's the flow rate of the pump you gonna use (GPH)?

 

[PhullD]

I'm afraid your plan A suffers from the same issue of my initial plan; risk of overfilling the OEM tank. When both tanks are directly connected and are filled together, filling continues till the fuel level passes the highest threshold level of the two, in this case it's the vent port of the AUX tank. If that is located higher than top of the OEM tank, you overfill it and get to the unknown zone of: does it damage the sensors? does it enter the evap pipe? and so on...


So, you shall either keep the AUX tank's threshold level lower than top of OEM tank, or fill them separately.


You can absolutely use the sending unit's variable resistor to detect the border condition and turn off your pump safely. It just needs a little bit of R&D, which is fine. What's the flow rate of the pump you gonna use (GPH)?

The diagram is not to scale, I’m not sure where the tanks sit relative to each other at the moment. The OEM tank is pretty tucked up there. When the auxiliary tank is mounted I’ll have to update this.

I’m just going to use the GM pump for the 2002 Blazer.

 

[Majcolorado]

This thread has been fantastic so far. Looking forward to seeing how this ultimately gets solved.

 

[AndrewVK]

it might be easier to just add a single larger gas tank. i know the titans are only like a 28 gallon or something.

arent the xterras 21?
im not sure truly how much front and rear room the xterra has compared to the frontier under there but the titan tank physically fit under it no problems.

the mounts arent that far off, some welding would be needed but it may be a better overall solution to the whole 9 yards that comes with this type of setup.

 

[PhullD]

it might be easier to just add a single larger gas tank. i know the titans are only like a 28 gallon or something.

arent the xterras 21?
im not sure truly how much front and rear room the xterra has compared to the frontier under there but the titan tank physically fit under it no problems.

the mounts arent that far off, some welding would be needed but it may be a better overall solution to the whole 9 yards that comes with this type of setup.

I would still put an Auxiliary tank in even if the Titan tank was installed >

 

[bluez]

it might be easier to just add a single larger gas tank. i know the titans are only like a 28 gallon or something.

arent the xterras 21?
im not sure truly how much front and rear room the xterra has compared to the frontier under there but the titan tank physically fit under it no problems.

the mounts arent that far off, some welding would be needed but it may be a better overall solution to the whole 9 yards that comes with this type of setup.

The Titan tank may fit under the frontier as you seem to say it does... but it definitely wont fit under the XTerra.
So on the Frontier forums ppl have swapped in 28 Gallon tanks from the Titan?

 

[Nasarno]

I just noticed that all my photo from Photobucket are disappeared. I should find a better host for my photos, then edit the links in all recent posts.