BMW’s i8 concept pushes the modern limits of the sport hybrid. Two seats, no roof, and mid-engined, this is not what you think of when you think hybrid. But nor is it some rip-snorting fire-breather: the engine behind the driver is only a three-cylinder. But then again, it’s mated to a lithium-ion powered electric motor for a combined output just shy of 400 horsepower.