“The most interesting thing in the world,” says University of Michigan professor and dirt biker Anna Stefanopoulou, “is balancing trade-offs to control complex systems.” Stefanopoulou works on electronic valves that could boost the fuel economy of conventional car engines by an estimated 10 percent and make practical exotic designs that are 30 percent more fuel efficient and free of nitrogen oxide emissions. A conventional engine regulates power with a throttle that controls airflow into cylinders; the timing of valves stays mechanically fixed. But the timing of electronic valves can vary infinitely, allowing the engine to “gain torque so fast it can break the crankshaft,” Stefanopoulou says. The native of Greece is developing such controls using sophisticated mathematical modeling, while high-end car companies “rely more on intuition,” says her Michigan colleague Jessy Grizzle. Stefanopoulou is also devising automated gears that would use engine compression to brake vehicles. She was already modeling the control of cars powered by fuel cells when the Bush administration dismantled an initiative to develop hybrid gasoline-electric vehicles–in favor of fuel cell power.