Ricardo built this HyBoost with two goals in mind: topping Toyota Prius fuel efficiency while skirting the cost, bulk, and weight of the Prius's two electric motor/generators and battery pack. The experiment is a timely one—every carmaker sees 2025's 54.5-mpg CAFE requirement looming, and most need help meeting it.
To create the HyBoost, Ricardo replaced the original 1.6-liter four-cylinder engine with a 1.0-liter EcoBoost three-cylinder and augmented that engine's turbo with a Valeo electric supercharger. Two years ago we speculated that BMW might use an electric supercharger to sharpen throttle response at low engine speeds. While that has yet to come to fruition, Audi has one under the hood of its RS5 TDI concept car.
Source: Road and Track