A pair of motors drives the Karma's rear wheels through a fixed-ratio limited-slip differential. Straddling the rear axle, the two motors are rated at a combined 402 hp and 981 lb-ft of torque. The motors are the Karma's sole means of propulsion, but the power used to turn them can come from either of two sources.
Like the Chevy Volt, the Karma is primarily an EV, powered by a 600-pound lithium-ion battery pack mounted longitudinally along the center of the car. It also serves as a structural member and results in a high center console running the length of the cabin. The pack contains a maximum of 20 kWh of energy, which it can deliver to the rear wheels in bursts as high as 241 hp. The capacity is sufficient for fifty miles of all-electric travel, says Fisker.
Once the battery pack reaches a 10 percent state of charge, the Karma switches automatically to its secondary power source: a direct-injected, turbocharged four-cylinder under the hood. The GM-supplied 2.0-liter engine was previously used in the Pontiac Solstice GXP and the Saturn Sky Red Line. As in those cars, it's rated at 260 hp-but this engine will never turn a wheel. Instead, it's connected directly to a 235-hp generator. The gasoline engine exhales through the front fenders the spent gases from combusting 9.5 gallons of premium unleaded stored onboard-enough for an additional 250 miles of range.
Combined, that's a total range of 300 miles-but the pocket-protector crew might have noticed something strange: neither the battery pack nor the gas engine can produce enough juice to fully power the electric motors. To get the full 402 hp that the two motors are capable of delivering, the Karma's driver needs to switch from Stealth (EV) mode to Sport mode by tapping the left steering-wheel paddle. Then, the Karma's power-management system uses both the battery and the generator to send the full monty to the motors.