Auxiliary Fuel Tank Options

[Scott Brady]

Since range is one of the major considerations for an Expedition Platform, I wanted to start a comprehensive thread on the subject.

Essentially, there are four ways of gaining range:

1. Vehicle efficiency: The better the fuel economy, the better the range out of the stock tank. This can be improved by keeping roof racks off, monitoring air pressure in the tires, tire tread design, tire width, etc. There are also modifications that can be done to improve the motors efficiency, etc. (example: changing from 4.10 to 5.29 gears improved my fuel economy from 13.8 to nearly 17 mpg, I also closely watch tire pressure).

2. Portable fuel containers: Like the Scepter Cans and similar. Mount these low in the vehicle as possible and only use cans that will not leak so that you can arrange them down low even in the passenger compartment. Avoid use on the roof rack (avoid the roof rack too).

3. Larger Factory Tank: Companies like Long Ranger and Transfer Flow make larger tanks to fit in the stock position. Ground clearance is often compromised.

4. Auxiliary Fuel Tank: You can install an auxiliary tank, which can even be factory options. Land Cruisers have many options. You can also install and fabricate a custom solution. Typically provides the longest range solution and lowest COG.

So, what has worked for you? This thread will allow us to catalog different options.

 

[Scott Brady]

Isuzu Trooper Tank in Tacoma

My choice was to use an OEM tank and mount it where the spare tire was located. My selection came to an Isuzu Trooper 22 gallon tank which provided me with 40.5 gallons and about a 650 mile range.

Before:

After:

Installation Document: Tacoma Auxiliary Fuel Tank Install

 

[Scott Brady]

Samuria Oversized Tank for use in Tacoma/Nissan/Truck

My 22 gallon monster is not for everyone, so I have researched other options. This has led me to a discussion with Gary from Petroworks (Fallbrook, CA), a very cool supplier of Suzuki parts and accessories.

They have designed a 15 gallon replacement tank for the Samurai, which will also make a great platform for an auxiliary tank. It has a 3/16" integrated skidplate and all of the fittings and sending unit. I think this could be a killer solution and is extremely reasonable @ $360.

I am working with Gary to get more details, including sending unit resistance and overall dimensions.

 

[Suty]

Scott, That would be a sweet deal. Keep us posted on dimensions etc... Since moving my Air Tank under the bed it would be a consideration for sure. Tu Compadre, Suty

 

[BMAN]

As the 60 draws closer to the day she might actually run again I have found myself poindering this exact idea. What's really out there and why hasn't someone stateside come up with a real bolt-in solution? I have thought about a custom poloy tank with steel skids to use as a transfer tank. Not quite there yet but I'm deffinately interested in seeing what others have done.

 

[calamaridog]

Fallbrook? That's not far from here:jumping:

I could use a few more gallons myself...

 

[Mike S]

...example: changing from 4.10 to 5.29 gears improved my fuel economy from 13.8 to nearly 17 mpg

Hard to see how making more RPM would improve fuel economy. Maybe you drive slower or meant changing to 4.10 FROM 5.29?

Also, the idea of carrying fuel in a container inside the passenger compartment is not a good one. Better mounted low as you suggested, but OUTSIDE the vehicle.

Another, perfectly viable option, is to install an overdrive, or a transmission with an overdrive top gear. I install a 5 speed in my Landcruiser - mileage is much improved.

Your advice on tires is sound, but you should not overlook the impact of tuning the engine correctly for driving conditions, and running a good synthetic oil.

Just a thot.

Mike

 

[Life_in_4Lo]

Hey Scott I didn't know you did this. It's very cool
The Sammy tank looks really interesting. Do you think it would work on a fzj80 (spare removed of course)?

Question- can you connect the 2nd tank to the main one so you fill both from the stock gas fill and then use a pump to transfer to the aux tank and back again while out on the trail?

My 22 gallon monster is not for everyone, so I have researched other options. This has led me to a discussion with Gary from Petroworks (Fallbrook, CA), a very cool supplier of Suzuki parts and accessories.

They have designed a 15 gallon replacement tank for the Samurai, which will also make a great platform for an auxiliary tank. It has a 3/16" integrated skidplate and all of the fittings and sending unit. I think this could be a killer solution and is extremely reasonable @ $360.

I am working with Gary to get more details, including sending unit resistance and overall dimensions.

 

[Scott Brady]

Hard to see how making more RPM would improve fuel economy. Maybe you drive slower or meant changing to 4.10 FROM 5.29?

Mike

Vehicle is operating in the prime torque band at 65 mph. With the 4.10 gearing, the truck would shift in and out of OD frequently, which also takes the transmission out of lock-up. Out of lock-up the efficiency suffers from the torque converters parasitic loss.

 

[Scott Brady]

Hey Scott I didn't know you did this. It's very cool
The Sammy tank looks really interesting. Do you think it would work on a fzj80 (spare removed of course)?

Question- can you connect the 2nd tank to the main one so you fill both from the stock gas fill and then use a pump to transfer to the aux tank and back again while out on the trail?

With the FZJ, you are in luck, as Long Ranger makes a split filler for your stock filler door. With the FZJ, I would recommend a factory 12 gallon (I think) unit.

 

[Scott Brady]

Because of Mike's great question, I thought it would be beneficial to talk about axle gearing and its relationship to fuel efficiency (thereby increasing range). Contrary to popular belief in the 4wd community, axle gearing should not be selected because of tire size, but as a calculation of peak torque.

So what is peak torque: That is the point when the maximum about of air and fuel can be drawn into the engine, creating the greatest amount of peak cylinder pressure.

In smaller displacement 4cyl and 6cyl gas motors, peak torque occurs high in the RPM band, which requires greater RPM to maximize engine efficiency. But it is also important to note that peak torque may not be required to maintain 55mph, but very well could be required to maintain 75mph.

In my Tacoma 3.4L example, peak torque is achieved at 3,600 rpm. At cruising speeds, you want to be from 75 to 85% of peak torque RPM's for maximum efficiency. So, at 75 mph (my typical cruising speed) I am at 83% of peak torque. With the stock 4.10 gears, I was at 61% of peak torque, and the truck could not hold the speed, requiring me to downshift and lose the efficiency of the lock-up. It also made overdrive worthless, leaving me with a 3 speed. One fewer gear for the speed range I operated in made the engine even less efficient.

 

[Mike S]

Scott

So basically the gear change let you use you 4th OD gear more often, instead of 3rd, right? This is a reasonable solution. I find that a lot of people run tires that are too large, and don't take time to figure out the total valve train gearing issues.

I my FJ60, the engine is well tuned and delivers peak torque at 1800 and 2700 RPM. I run 31X10.50 MTRs which are about as big as can be run with the 3:73 stock gearing, runnig in 5th (OD) and still have adequate power for 4th gear driving in the hills. I could go slightly taller, and change to 4.11 RE gearing to get slightly more response from the throttle, but would see no net effect in mileage.

I think, for me, that the answer to better mileage is a more powerful and effiicient engine - turbodiesel or current generation 5.3L Vortec. I love the 2F, and, if I never pulled a trailer, I would stay wth it, as it runs great. But pulling the trailer over Lolo Pass at 35 in third makes me think about the Vortec solution. Faster, more power, better mileage. So there is yet another alternative that sounds wrong, but will probably deliver about 17 MPG in my truck with the H55F tranny, with 3:73 gears and 33X10.50 (metric equivilent) on 16" rims.

Toyotas are not known for power, anyway.

M

 

[HenryJ]

My choice was to use an OEM tank and mount it where the spare tire was located...
Installation Document: Tacoma Auxiliary Fuel Tank Install

I followed this install and it was the basis for my second auxiliary tank.
Auxilary Fuel Tank
It has been just over two years now since I installed the Isuzu tank and I finally get around to installing the auxiliary fuel tank shield.

It only took a couple hours to cut off the stock brackets and fab some to bolt it up. I don't know why I had put it off this long.

I guess the incentive to have things ready for Utah next year helps quite a bit. One less thing on the list.
All three tanks give me a range close to 800 miles.

 

[ntsqd]

With regards to peak Torque & most ideal engine operating operating speed; It has been my observation and the results of subsequent investigation that the best Brake Specific Fuel Consumption (BSFC) occurs at peak torque. This is extremely consistant in all of the dyno runs made by reputable shops that I've reviewed as well as those I've witnessed on the dyno I did the mechanical design & fabrication of.

BSFC is defined as the most Torque produced for the least fuel consumed.

With that in mind, I'm curious what drives the 75%-85% of peak Torque RPM recomendation?

In my own experimentation with this I have found that 95%-100%, but NOT 105% of peak Torque RPM yields me the best mileage ('84 22R - carb'd, 4.88's, 33-10.50's, G series trans, ~3" lift). With the current cam that is about 3200 RPM, under 3k in 5th is obviously lugging the engine.

 

[shortymav]

With my car being a SWB space is at a premium at the moment im getting round town 13-15l per hundred KM. the tank is a 95l one and im looking to expand my range on the highway i can get round 10-12l per hundred KM so based on this in order for me to get 1000km Plus with a comfortable buffer i need around 130-150l I was able to get a 60l tank custom made under the drive that sits next to the transfercase and chassis but doesnt rub or contact on anything.

now i have the ability to carry 155l of diesel, getting a 40l water tank fabbed up soon too