TURIN, Italy – Toyota is ready to take the Frankfurt auto show by storm with a small hybrid powered by a big engine – 420 hp to be exact.
The Yaris Hybrid-R concept is not intended for serial production, but rather to draw attention to Toyota’s 5.5 million global hybrid sales since the introduction of the Prius in 1997. The auto maker says it also points to the future of its hybrids, which will be capable of faster speeds and sportier performance.
Renderings of the showcar are being released this week by Toyota ahead of Europe’s biggest auto show.
The hybrid’s muscle comes from Toyota Motorsport’s 1.6L 4-cyl. turbocharged global race engine that delivers 300 hp to the front wheels. Two 45-kW (60-hp) electric motors power the rear wheels. Energy is recovered from heavy braking and deployed to the rear wheels for extra boost.
As with the race car, the energy is stored in a supercapacitor, which has a higher power density and a fast power charge/discharge speed. The technology has been successfully employed by Toyota Racing’s TS030 Hybrid race car in the FIA World Endurance Championship.
The powertrain system is perfectly suited to the requirements of racetrack driving, which requires brief and immediate bursts of power. In track mode, the rear electric motors reach a combined maximum power of 120 hp for up to five seconds per charge, reflecting the higher frequency of braking and acceleration events during circuit driving, Toyota says.
A third electric motor, also 45/kW, is located between the engine and the 6-gear sequential transmission and operates as a generator in two different cases: during deceleration to feed the supercapacitor and during acceleration to directly power the rear electric motors.
This takes place only when engine output exceeds the grip potential of the front wheels. In this case, the generator works like a traction-control system, redirecting the torque as electric energy to the rear wheels to boost the acceleration and improve the handling, rather than to simply limit the engine power.
The rear motors greatly influence the Yaris Hybrid-R’s handling characteristics during cornering by altering the distribution of torque between the left and right rear wheels. On its turn, each motor operates independently as a generator or a motor to achieve the same effect as an intelligent torque-vectoring differential.
Toyota says depending on the radius of the curve, the system can send more torque to the outside rear wheel, allowing higher cornering speeds into the corner (middle-speed curves); apply more braking force to the inside wheel (fast curves); or even brake and accelerate each wheel independently (slow curves) to adjust the yaw effect for a better line, and to limit steering angle and understeer.