Double Tank Mileage Contest

I'm sponsoring a year long, contest for Prius, gas-only, hybrid owners to achieve twice the USA EPA estimated range on a single tank:

• Contest runs June 1, 2014 to May 31, 2015
• Gas-only, Prius, no plug-ins including after market
• International, open to anyone

The amount of fuel consumed and distance is documented by a photo of the ending trip meter. There is no need to overfill the tank or run the tank dry. Simply keep track of the gasoline consumed on the trip meter, miles/MPG or the metric equivalent. Once you've reached the required distance, stop and take a photo of the tripmeter and post in this thread by quoting your initial, entrance announcement . . . with the photo.

This table shows the requirements by Prius, gas-only model:

	EPA Range	2x tank	fuel(*)	model
1	488 mi	976 mi (1562 km)	11.9 gal (45L)	2001-03 Prius @82 MPG
2	547 mi	1094 mi (1750 km)	11.9 gal (45L)	2004-09 Prius @92 MPG
3	595 mi	1190 mi (1904 km)	12.1 gal (45.8L)	2010-current Prius hatchback @100 MPG
4	500 mi	1000 mi (1600 km)	12.1 gal (45.8L)	2012-current Prius v @84 MPG
5	475 mi	950 mi (1520 km)	9.7 gal (36.8L)	2012-current Prius c @100 MPG

(*) US gallons, not Imperial and any 'overfill' has already been added to the tank amount. Overfilling the tank adds unnecessary weight.

To enter the contest:

1. On or after June 1, post a start announcement in this thread with year and model of Prius and your Prius photo showing it is not plug-in or plug-in modified.
   1. Optional, identify your city and/or favorite Prius dealer. I will contact that dealer to give them the option of sponsoring your windbreaker or additional prizes which allows us to add more awards.
2. Drive until the 2x tank distance has been achieved on the equivalent of one tank of gas. Note, if you reach 1,000 miles but not the 2x tank distance, there will be runner-up, t-shirt prize.
   1. If your odometer is off, post a GPS or highway mile marker report showing the calibration constant. For example, if driving over sized tires, the indicated distance will be smaller than the actual distance which is the "2x" criteria.
3. Take a photo of the trip meter showing MILES (KM) and MPG (L/100KM) and reply with a quote to your first post.
   1. The calculated fuel burn can not exceed the tank capacity by more than 1.7%.
4. Tweaks: no plug-ins nor towing. Everything else is OK but please share. Team driving is OK but only one award per car.

To start the contest, I am budgeting 10 awards, one per Prius:

• Windbreaker jacket - your size and all colors at once (for men, black, women have other color options)
• Lettering on back showing something like this:
• I am looking for award sponsors so your entrance announcement with the City/State/Provence is important.

Robert J. Wilson
Huntsville, AL
256-961-9391 (work)

 

It is fair to ask where the numbers come from:

The EPA uses the combined MPG and the tank capacity:

• MPG = range_miles / tank_gallons
• tank_gallons = range_miles / MPG
• range_miles = MPG * tank_gallons

Here is the source data:


Nobody has to do this on just one tank, only the trip meter photo is needed. For example:

• 1000.8 miles / 91.8 MPG = 10.9 gallons
  • The 10.9 gallons could be entered in as many different station fill-ups as necessary. Although I was doing a full tank test last summer, a full tank is NOT necessary for this contest.

Since we are only using a photo of the tripmeter, there is no need to try this on a single tank. Visit a gas station as often as you want. This is why I clarified the rules:

Past driving stunts have described "burping the tank" and other tricks to get a maximum tank fill. But these risk flooding the carbon canister or getting gasoline between the bladder and the tank. Both are expensive repairs so DON'T DO IT. Just use the tripmeter to measure the amount of gas burned over the distance covered.

Using the tripmeter to measure the amount of gasoline burned takes math, dividing the tripmeter miles by the MPG. But it means you can add gas to the tank anytime. It also means, as you learn how to do the math, that you'll be monitoring the progress early enough to tell IF you'll meet the 2x tank threshold.

Last summer, I was doing an 'old school', stunt driving, an actual tank. Then I realized a photo of the tripmeter solves a lot of problems:

• No need to overfill the tank - so I've added 7% to the published, tank capacity to account for any overfill attempts.
• No need to run a tank dry - the fuel consumed is from the tripmeter photo. Add gas as often as desired.
• Pump variability - the tripmeter photo provides the amount burned and distance covered.

As the indicated miles and MPG reach the end, the MPG does not change rapidly. If the miles are close to either the 1,000 mile 'door prize' or the 2x threshold, take a photo and continue driving. You want the "miles / MPG" to be equal to or under the maximum for your car. Just calculate how many more miles at that MPG and you'll know if it is possible to meet the threshold. This is a fair reading of the tripmeter data so use it.

Bob Wilson

 

I've run our 2003 out of gas about 40 times and 7-8 times in our 2010 as part of my gasoline studies. I appreciate the concern but there are mitigations.

There is a small amount of unusable gas that as the inlet comes open still passes with vapor through the shaft connected pump and evaporation is a powerful coolant effect. Also when the pump is unloaded, it speeds up increasing the back EMF and reducing the heat load. But I am sympathetic to "heat is the enemy."

I was fully prepared to replace the tank in the 2003 or removable fuel pump assembly in the 2010. There are some questions that can only be answered by doing the experiment.

Bob Wilson

 

ANNOUNCEMENT

I'm entering our 2003 Prius:

• 976 miles
• 11.9 gallons

Bought in October 2005 with 49,300 miles, it has just passed 160,000 miles. But after 9 years in my hands, it is not quite stock any longer.

STRATEGY


The front tires are 106% oversized which means the indicated miles has to be multiplied by 1.06% to get the true miles which means an indicated, 921 miles, gives the 976 miles required. Tires at maximum sidewall for Sumitomo T4s, 51 psi.


Four-wheel alignment for toe and camber. This included a front camber bolt.

Cruise control speed target, 25 mph:

I'll shift my schedule to start early in the morning, around sunrise, so my slow speed won't lead to road rage. It will also avoid the heat of the day to drive without air conditioning.

Each trip will be extended to at least one hour by 'doing laps' such as on this loop:

There are others mapped around Huntsville. I'll use a Graham miniscanner to monitor engine performance and shift into "N" anytime traffic, and terrain makes it practical and the engine is off.

To reduce aerodynamic drag and accelerate warm-up:

Use the lower air inlet block but I may reinstall my engine thermostat hack:

This spoofs the engine thermostat circuit to allow hybrid mode to start at 40C instead of waiting for 70C.

Series of tanks, running dry each time to test different, local brands:

Right now, I'm thinking to test:

• straight gas
• Shell E10
• generic E10 Costco

OTHER MODIFICATIONS

• The traction battery is upgraded to NHW20 modules done in November 2009.
• The transmission oil is Type WS, the same as the NHW20, and not the original of Type T-IV.
  • It is on the 5th change with dropping and cleaning the pan each time and currently has ~20,000 service miles.
• The engine is using 0-20W, Mobil One, same as our 2010 Prius.
• The radio antenna is stowed since there is nothing on AM or FM worth listening.
• We also have a two-camera, front and back, dashcam recorder with GPS.
• It has a backup camera and GPS, rear view mirror.
• A 'beeping' LED backup light is on one side.
• There is a 2", tow receiver hitch.
• It also has a 1kW, modified sine-wave inverter and is on its 3d, 12V battery, an Odyssey 925.
• The tires are Sumitomo T4s with ~50,000 service miles
  • The front are larger diameter than the rear which improves high-speed stability
  • The front are about ready to be replaced.
  • The rear are showing excellent tread.

Bob Wilson

 

Just this one since the goal is to have a year long, world-wide contest . . . not against others but against the 2nd Law of Thermodynamics. <grins>

Now I realize I'm a little anal about documenting what I'm doing and that should NEVER stop anyone from posting what they feel comfortable. The main thing is the model of Prius and their intention to start the effort. With a year-long window, precision is not terribly important but we need to know someone is trying for a windbreaker.

Bob Wilson

 

Ok, I took this photo last night:

Due to the oversized tires, that is actually 105.8% * 68.0 MPG or 71.9 MPG.

• 159 mi / 68.0 MPG = 2.34 gallons burned
• 11.7 - 2.34 = 9.36 gallons left to burn in tank

So looking at my earlier benchmarks:

So at 25 mph, my target cruise control speed, we're looking at 80 MPG:

• 9.36 gallons * 80 MPG = 748.8 miles
• 159 + 748 = 907 miles (estimated total miles)
• 907 / 11.7 = 77.5 MPG (estimated ending miles)

At this rate, it does not look like I'll meet the 2 * 41 MPG = 82 MPG. But I have a cheat, oversized tires, 5.8% larger. So the true MPG would be 105.8% * 77.5 MPG = 81.99 MPG. I have a fair chance to meet the challenge. Driving in warmer weather, ~85F, should do it.

So right now, I've got a lock on reaching 500 miles and setting the bar for the 2001-03 Prius. With luck, I might hit my goal. I'm at 158/907 = 17.4% of the ultimate goal. But once I reach 500 miles, I'll be in a better position to determine if I continue this effort to the end or make one more change to the car.

Bob Wilson

 

A day later, another round trip to work:

• 205 mi / 69.7 MPG = 2.94 gal
• 2.94 gal - 2.34 gal = 0.50 gal fuel burned
• 205 mi - 159 mi = 46 mi (indicated)
• 105.8% * 46 mi = 48.67 mi (true)
• 48.67 mi / 0.50 = 97.3 MPG (true)

A couple of more days like this and I'll be well on the way to my goal.

Bob Wilson

 

Another day and:

• 238 / 70.2 = 3.39 gallons total
• 3.39 - 2.94 = 0.45 gallons burned this trip
• 238 - 205 = 33 miles indicated, 34.9 miles actual
• 34.9 / 0.45 = 77.6 MPG actual, matches expectation

There will always be an unpredictable, traction battery state of charge that can change between the beginning and end of each trip. This alone could account for significant, per trip variations in the shorter MPG metrics. Still the long term trend is as expected.

Bob Wilson

 

Back home again:

• 4.34 gallons
• 324.8 miles true
• 74.8 MPG true

Right now, it looks like (11.9 - 4.34) * 74.8 = 890 miles. I won't reach my goal on this tank . . . darn it!

Oh well, might as well see how far it can go.

Bob Wilson