The technology behind the 4th generation Prius
Toyota has announced further technical details about the new, fourth generation Prius, ahead of the model being presented at the 44th Tokyo Motor Show, from 28 October.
In its design and engineering, the new Prius is a car that has been conceived to be in harmony with society. The application of a wide range of new technologies takes safety and driver assistance to a higher level, improves comfort and gives clear delivery of vehicle and performance data and information.
The foundation stone for creating the new Prius is the Toyota New Global Architecture, a concept that helps enable significant improvements in efficiency, while also delivering a vehicle platform with a low center of gravity, securing better driving quality, ride comfort, quietness and a more engaging, dynamic design.
Comprehensively improved Prius full hybrid system
Toyota has made significant improvements in its new generation full hybrid powertrain, reducing losses, redesigning and relocating key components and reducing weight. The result is an improvement in efficiency, achieved through detailed changes to the transaxle, engine and combined hybrid system. The new Prius is set to deliver an 18 per cent improvement in emissions and fuel consumption, the largest leap yet in cleaner running and efficiency in successive generations of the model. European homologated emissions and fuel consumption data will be announced later.
Petrol engine with world-leading thermal efficiency
The new Prius retains the 1.8-liter VVT-i gasoline engine featured in the current model, but changes to the unit have taken its level of thermal efficiency to a world-leading 40 per cent, a figure comparable to a diesel engine.
Key developments include a Toyota-first dual cooling system, which automatically reduces the coolant flow volume in the engine to enable faster engine warm-up and the adoption of a low-viscosity oil to reduce friction between moving parts. Fuel efficiency in cold weather conditions has also been improved thanks to a new system which uses a coolant water selector valve to accelerate engine warm-up, while maintaining cabin heater performance.
New piston and air intake port designs create greater tumble and swirl inside the cylinder, and the volume of the exhaust gas recirculation has been increased, which further helps reducing NOx emissions.
Transaxle and electric motor
The transaxle and motor have been redesigned, delivering a reduction in their combined weight. The motor itself is more compact and gains a better power-to-weight ratio. Notably there is about a 20 per cent reduction in mechanical losses through friction compared to the previous model. The reduction in size has been made possible thanks to the motor’s new multi-axle design: the length of the transaxle has been made shorter by locating the drive motor and electric motor/generator over multiple axles, instead of the previous single axle. The planetary gear arrangement in the reduction gear has been replaced with parallel gears, which further helps loss reduction.
Power Control Unit
The use of a loss-reduction device in the power control unit cuts losses by about 20 per cent. With a more compact design, the unit can now be positioned directly above the transaxle.
The auxiliary batteries have been moved from the trunk to the engine compartment and the relocation of the hybrid battery beneath the rear seats (see below) also helps free up more luggage space, Trunk volume has increased to 502 liters in the new Prius.
The new Prius features a new nickel-metal hydride (NiMH) hybrid battery, considered by Toyota to be the optimum choice to meet market requirements. The battery has been relocated beneath the rear seat, avoiding any intrusion in trunk space.
Technical specifications of the new Toyota Prius
4-cylinder in-line, DOHC
98 DIN hp/72 kW @ 5,200 rpm
142 Nm @ 3,600 rpm
72 DIN hp/53 kW
Hybrid battery material