The Tango was never designed to be the most fuel-efficient car in the world. To do that, safety and rollover threshold would be compromised. The fact that the 3,300-pound Tango made it to finals in the Automotive X-Prize competition is quite remarkable.
Following is the official data from the efficiency event. Note that although the Tango was less than 1% short of the required MPGe to go to Argonne for the Validation Stage, it needed 104 MPGe, because of the emissions requirement. They use a national grid average to calculate the emissions from creating the electricity for the grid. It's obviously very unfair when considering solar charging, but even if the California or Washington grids were used because of the predominance of hydro and natural gas, it would not be an issue. It's all of the electricity generated from coal that skews it against EVs.
Following is a breakdown of the Tango's efficiency for each cycle independently.
89.07 MPGe. (387.269 Wh/mi.)
This was a combined Urban, City, and Highway cycle.
The Urban Cycle was 74.34 MPGe (464.75 Wh/mi.)
It was 16 miles of start and stop many times per lap at lower speeds.
The City cycle was 58.86 MPGe (586 Wh/mi.)
This was 30 miles of acceleration to 50 mph and brake twice per lap, and then 40 mph in-between. It's a 2-mile oval.
As you can see, the starts and stops w/o regen and a 3,300-lb car really hurt efficiency. The motorcycles that competed in our class were getting 180 to 200 MPGe, but only weigh 1,300 lbs. The way the rules were written, there was no way to beat them.
The Highway Cycle was 112.21 MPGe (307 Wh/mi.)
This was 90 miles of 50 mph, but stopping once every 5 laps (10 miles).
All of the above Wh/mi calculations are reading from the meter on the wall, and includes all inefficiencies including losses at charging and at the cells.
During the Urban Cycle, I had to run the A/C constantly. The rules were that if the cabin temp exceeded 95°, a full penalty lap would be added. In the driver's meeting, they pleaded with us to follow the rules and not allow cabin temp to rise above that limit. The other teams in our class did not run A/C. One or two used buckets of ice to keep their cabins cool. Many of the teams went to the competition with cars built especially to win the competition, so the purpose of the competition, to provide vehicles that people want to drive, was virtually ignored in many cases
Durability was an event at Shakedown. It was 40 miles of the roughest track you can imagine. I was within 2 seconds per lap of the fastest car which was a Factory-5 electric race car. I had a blast driving lap after lap pushing the limit at every turn, and then rewarded by never having to stop. I lapped all the other cars in my group several times.
In the finals Range Test, I ran out of juice at 99 miles. I was half way around the final lap when I ran out. I heard that the temperature was recorded at 120° on the lawn that afternoon. I ran with A/C on full blast, but it seemed to lose efficiency. The evaporator might have frozen up. In any event, drawing 8 amps for nearly 2 hours ate up 5 kWhrs or 20 miles of range. I thought that I had plenty of margin, but miscalculated. Being eliminated because of efficiency, I didn't have a lot to lose, and thought that I could at least run the 100 miles without cabin temp penalty. So 49 1/2 laps is all she wrote with the A/C compressor running at 6,500 rpm.
The final event was a tie-breaker for all of the teams that made it through the qualification runs. It was run at any speed between 45 and 70 mph, but had a very tight chicane midway around the track. They let me run with the other eliminated cars in a demonstration run. Driving at 60 to 65 mph, I lapped every other car at least 3 times in my group during the 100 miles, which I finished with 10% of charge remaining. Luckily, it was not so hot so I never ran the A/C.
I got exactly 100 MPGe on that run of 100 miles using 34 kWhrs, or 340 Wh/Mi at the meter and had 10% state of charge left at the end.
Those of us that were eliminated also got to run the acceleration, braking, and emergency lane change events as a demonstration class. The Tango passed these with huge margins.
David Champion, Director of Consumer Reports Automotive Testing said that I had the fastest time of any of the cars in the X-Prize competition by running the emergency lane change at 51 mph. The test had to be completed at 45 mph to pass. I passed the test on the first try at knockout, but forgot that there was a camera attached on the side at the finals and took out a cone (and the camera) on the first run. The second was at 51 mph.
The CO2 numbers for the national grid today have little to do with CA where many times more EVs will be sold than elsewhere in the country, and doesn't account for the fact that the grid gets cleaner every year with added wind, solar, and even improvements to coal burning plants.
All in all, the Automotive X-Prize competition was a very worthwhile event. I look forward to the awards ceremony at the White House on September 16, where I'll be with the Tango, the winners of the 3 prizes, and the other finalists.