Toyota Yaris Hybrid-R concept, 2013 Frankfurt Auto Show
The Yaris Hybrid-R develops a total 414 horsepower from a gasoline-electric hybrid powertrain, consisting of a turbocharged 1.6-liter four-cylinder engine working in parallel with two electric motors to form a through-the-road all-wheel-drive system. The setup also makes use of a supercapacitor to harvest and store energy, just like the TS030 Hybrid prototype.
The engine, which rates at 300 horsepower on its own, is a turbocharged four-cylinder unit with direct injection and was developed by Germany’s TMG in accordance with various international sporting regulations. While the engine drives the front wheels, each rear wheel is powered by a 45-kilowatt (60-horsepower) electric motor--the same as that used in the standard Yaris Hybrid. The two electric motors work as electric generators when the car is braking, and supplement the gas engine’s performance under high load.
As mentioned, energy recovered under braking is stored in a supercapacitor. Compared to the standard nickel metal-hydride battery used in the Yaris Hybrid, the supercapacitor has a higher power density and a fast power charge/discharge speed. This makes it perfectly suited to the demands of track driving in delivering brief, immediate bursts of power.
The level of power depends on the duration of energy delivery required. So, when Yaris Hybrid-R is running in “road” mode, the supercapacitor releases energy for a maximum 10 seconds per charge, and the total power of the two electric motors is reduced to 30 kilowatts (40 horsepower). In “track” mode, the motors reach a combined maximum of 90 kilowatts (120 horsepower) for up to five seconds per charge, reflecting the more frequent braking and acceleration in circuit driving.
But the Yaris Hybrid-R has one more electric motor. This third unit, also rated at 45 kilowatts (60 horsepower), is located between the engine and six-speed sequential transmission. This operates as a generator, both during deceleration to feed power to the supercapacitor, and during acceleration to power the rear electric motors. The latter only happens when engine power and torque exceed the front wheels’ grip limit.
Thus, the generator works like an advanced traction control system, redirecting torque as electric energy to the rear wheels, to boost acceleration and improve handling rather than simply to limit engine power. A similar system is utilized in Ferrari’s LaFerrari supercar. The rear electric motors also improve handling; each motor can be used independently as a generator or a motor to achieve the same effect as a torque vectoring differential.
Such electrical systems will become commonplace in performance cars. Not only do they reduce fuel consumption but they also improve performance and handling.