Toyota said it had made significant improvements to its new generation full hybrid powertrain in the redesigned 2016 Prius, reducing losses, redesigning and relocating key components and reducing weight. Extensive changes to the transaxle, engine and combined hybrid system, generate an expected 10% improvement in US market EPA estimated MPG on core models, with an Eco model that will achieve an even greater improvement.
The latest Prius retains a 1.8-litre VVT-i petrol engine but it has been completely re-engineered to achieve a claimed ground-breaking maximum thermal efficiency of 40%. This was enabled in part through the use of a large-volume exhaust gas recirculation (EGR) system and improvements in combustion efficiency. Additionally, a redesigned air intake port improves airflow inside the combustion chamber, while the coolant passages have been redesigned to optimise internal engine temperature. Friction created by the piston skirts, rotating parts and the oil pump has been reduced, while the use of low-viscosity oil reduces friction between sliding engine components.
Fuel efficiency was also boosted by improvements to heating performance. An active grille shutter has been added to open and close the grille as necessary in response to outside temperatures. The exhaust heat recirculation system has also been improved and made more compact. This recycles exhaust heat from the engine into the coolant to be reused in the heaters and to warm the engine. Cold weather fuel efficiency has also been improved by introducing an engine coolant selector valve and adding a new system which accelerates engine heating.
Transaxle and electric motor
The transaxle and motor have been redesigned, delivering a reduction in their combined weight. The motor itself is considerably more compact and gains a better power-to-weight ratio. Notably there is a 20% reduction in mechanical losses through friction compared to the previous model. 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%. With a more compact design, the unit can now be positioned directly above the transaxle.
New lithium-ion or nickel-metal hydride hybrid batteries
The 2016 Prius will be available with either a new lithium-ion or a new nickel-metal hydride hybrid battery. While the batteries use established technology, Toyota has succeeded in increasing their energy density, which means more power can be obtained from a smaller unit. This in turn has allowed the battery to be relocated beneath the rear seat, increasing cargo space.
A hybrid that handles
The TNGA concept delivers an increase of more than 60% in body torsional rigidity, compared to the previous model, by using laser screw welding (with a greater number of weld points), structural adhesives and uniquely shaped frame structures. In addition, the amount of high-tensile strength steel has increased from 3% to 19%. These enhancements with a new double wishbone rear suspension and a lower centre of gravity result in a hybrid "with a sporty ride", the automaker claimed.
New updates to the hybrid system software improve the feel of acceleration, giving a smooth and direct response in a lower rpm range. To improve brake feel and reduce noise, the 2016 Prius utilises a newly-developed active hydraulic booster for its regenerative brakes.
The TNGA chassis allows for lower lines, while retaining the Prius's signature triangular silhouette. Body height has been reduced by 20mm and the high point of the roof has been moved 170 mm forward, ensuring plenty of headroom for front seat passengers while also contributing to excellent aerodynamics and an impressive 0.24 coefficient of drag (Cd). The lower centre of gravity has also allowed the nose height to be brought down by 70mm and the rearmost section of the bonnet by 62mm, improving the driver's forward view.
Standard bi-LED headlamps are fitted, which use a single lens for both high and low beam operation.
The new instrument panel has a slim, sculpted form, with optimum positioning of the gauges, displays and controls. White accents on the steering wheel and front console are used.
New seats provide more comfort and support. Innovations in the materials and thicknesses used for the cushion pads help take the strain off the hips and create a more comfortable feel for passengers.
Improvements have also been made to the cushioning of the rear seats in order to match the higher comfort levels achieved in the front seats. Although the car's height has been reduced, this is not at the cost of space; an innovative ceiling design has increased headroom compared to previous models.
New infotainment and comfort
Toyota has improved the look and performance of the multi-information display in the driver's instrument panel. Data and images are now presented in full colour with high resolution graphics on dual, 4.2-inch multi-information display screens. The right-hand section presents speed, fuel level and other basic data and the left-hand section is a multi-display where the driver can select preferred content using a switch on the steering wheel.
There is also a new colour head-up display, which projects essential vehicle data and alerts on to the lower section of the windscreen, making information instantly and easily readable.
The Smart-flow (S-FLOW) air conditioning system improves efficiency. It detects whether the front and rear passenger seats are occupied and adjusts ventilation and heating performance accordingly, minimising air flow around any empty seats. This results in making the cabin environment more comfortable and also helps improve fuel efficiency.
Optional advanced technologies
Toyota said the new Prius makes a significant advance in active and preventive safety measures with the optional Toyota Safety Sense P package that includes a pre-collision system with pedestrian detection. The system uses a millimetre-wave radar and a single-lens camera with integrated control to detect both cars and pedestrians. The package also comes with full-speed dynamic radar cruise control.
Intelligent parking assist uses ultrasonic sensors to detect surrounding objects and identify parking spaces.
The Prius reaches US dealerships early in 2016.