Toyota provides some details on Yaris Hybrid-R 420hp powertrain; three 45 kW motors

The Yaris Hybrid-R features three 45 kW electric motors, one on each rear wheel and a third between the engine and transmission that operates as a generator. This third motor can act as an advanced traction control system. Click to enlarge.

At the Frankfurt Motor Show, Toyota will showcase the Yaris Hybrid-R concept, created as a showcase of possible ideas for the development of hybrid technology for maximum performance and increased driving pleasure. Toyota has now provided a few additional details about the powertrain in advance of the show.

The front wheels are driven by a 300 hp (224 kW) 4-cylinder 1.6 turbo gasoline direct injection engine specifically developed by Toyota Motorsport GmbH (TMG) according to the rules of the International Automobile Federation (FIA) for a Global Race Engine to be utilized in various motorsport disciplines.

1.6L GRE engine. Click to enlarge.

At the rear, each wheel is individually powered by a 60 hp (45 kW) electric motor—the same as those used in the standard Yaris Hybrid. Taken together, the hybrid powertrain system develops a total system output of up to 420 hp (313 kW).

The two electric motors work as electric generators during the braking phase, and supplement the petrol engine during the accelerating phases.

Just as in the TS030 HYBRID, the energy recovered during the braking phase is stored in a supercapacitor. Compared to the standard NiMH hybrid battery, the supercapacitor has a higher power density and a fast power charge / discharge speed. It is well-suited to the requirements of sporty driving on track, which requires brief and immediate bursts of power, Toyota said.

The level of power depends on the duration of energy delivery desired. In road mode, the supercapacitor releases the energy recovered under braking for a maximum duration of 10 seconds per charge and the total power of the two electric motors is reduced to 40 hp (30 kW). In track mode, the rear electric motors reach a combined maximum power of 120 hp (89 kW) for up to 5 seconds per charge, reflecting the higher frequency of braking and acceleration events during circuit driving.

A third 60 hp electric motor, located between the engine and the 6-gear sequential transmission, operates as a generator in two different cases: during deceleration to feed the supercapacitor and during acceleration to directly power the rear electric motors.

The latter will only happen when the engine power and torque exceed the grip potential of the front wheels. The generator behaves like an advanced 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.

Rear electric motors—one per wheel—can greatly influence the Yaris Hybrid-R handling characteristics during cornering by altering the distribution of torque between the left and right rear wheels.

Each motor can be used independently as a generator or a motor to achieve the same effect as an intelligent torque vectoring differential.

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, to limit steering angle, and understeer.