The sleek black race car tore off in such a hurry that its fat tires slipped and squealed in response.
Driver Cheryl Liu, her 130-pound frame clad in a jumpsuit and helmet, huddled with her University of Pennsylvania teammates on the asphalt. On a cool day when the roadway was slightly damp, should she hand over the wheel to someone with a little more heft?
It was a good call. For the second time in three years, Penn's team of student engineers boasted the top-performing electric car at the international Formula SAE competition in June, taking the gold medal in a field of 21 collegiate entries.
The students spent months designing, building and testing their precision machine before the event in Lincoln, Neb., where they finished first in five out of eight categories.
One of those was acceleration, after junior Matt Mendivil took over the cockpit, driving the 75-meter course in 4.095 seconds — equivalent to going from zero to 60 mph in a brisk 2.6 seconds.
That is much faster than most production cars on the market — in part because, unlike internal combustion engines, electric motors can instantly generate maximum torque. In better conditions, the Penn vehicle can hit 60 mph in just 2.5 seconds. (Tesla's Model S, a top-of-the-line electric car, has been clocked at 2.3 seconds.)
Driving the Penn car, nicknamed REV 3, is a gas, said team co-manager Connor Sendel, a dual major in mechanical engineering and business.
"It's pretty crazy," he said. "It's fast. It's fun. And it's a race car."
More than 50 students played an active role in creating this year's car. Though she did not post the winning time as a driver, Liu, along with team member Alex Shea, played a crucial role in building the car's body panels out of carbon composite material.
The two made molds for the panels out of a wood-based material called medium-density fiberboard, and shaped them using a giant router at Leading Edge Composites, a team sponsor based in Coatesville. Then they laid on the sheets of carbon, which were infused with resin so they would cure into race-ready hardness. Eventually, the carbon panels were attached to the car's tubular steel frame, for a total weight of 400 pounds.
Among the vehicle's special features: an aerodynamic contraption jutting from the back that untrained observers have referred to as a spoiler. The correct term is "rear wing," said Liu, who earned her undergraduate and master's degrees this year and now works for a robotics startup in Utah.
"It gives you more downforce," Liu said. "It helps with cornering."
Other students devised the car's electrical system, led by Johnathan Chen and Jay Fleischer, while Sendel and co-manager Sina Golkari handled the business and operations side. The mechanical component was overseen by Mendivil and Liam Cook, while the overall team captain was Dan Shanks, who also took a turn as driver at the competition.
The budget for the car was just $85,000, Golkari and Sendel said. The true cost ran into the millions, including sponsor donations of parts, software, and expertise, the students said.
Each year, competitors have to enter a new vehicle, but that does not mean the car has to be built entirely during that calendar year. Over the years, the Penn students have learned that it makes sense to have teams working on several years' cars at any one time, said faculty adviser Andrew Jackson.
"We don't just go 'Phew' at the end of the year and start again from scratch," Jackson said.
He said Penn already has a good start on 2018, as the students finished the frame for that year's car several months ago.
These racing cars bear only a passing resemblance to the typical electric car on the highway, but lessons from the racetrack can be useful in the real world, Jackson said. Auto-manufacturer representatives who help judge the competition have been known to hire students on the spot, he said.
A professor of mechanical engineering, Jackson came to Penn in 2010 after a long career working with lubricants in the automotive industry, most recently at ExxonMobil. Though he has a background with an oil company, Jackson predicts that with ongoing improvements in batteries, electric cars will continue to gain in popularity.