It will deliver emphatic improvements in fuel efficiency, environmental responsibility and driving performance.
When Hybrid Synergy Drive made its debut in the current Prius, it was voted 2004 International Engine of the Year, and went on to win the Green Engine of the Year title for the last five years in a row. For new Prius it has been comprehensively revised and improved, with more than 90 per cent of its components redesigned to create a lighter, more compact system, with a focus on increased power, further reductions in real-world fuel consumption and improved cold weather operation.
The result is that new Prius remains the undisputed reference point for mainstream vehicle hybrid technology, setting new standards in innovation, design and driving enjoyment.
System power output has been increased by 22 per cent, from 109 to 134bhp and, with performance to match a conventional 2.0-litre petrol vehicle, new Prius will accelerate from 0 62mph in 10.4 seconds.
At the same time overall fuel economy has been improved by 10 per cent, new Prius returning 72.4mpg in combined cycle driving. The adoption of a larger, 1.8-litre engine reduces the rpm during high-speed driving to give a 10 per cent gain in long-haul cruising fuel efficiency. And with more torque produced at lower engine speeds, new Prius offers more relaxed cruising performance, too.
Prius easily exceeds the Euro 5 emissions standards, producing 89g/km of CO2. And when operating in EV mode at speeds up to 30mph, it uses no fuel and produces zero exhaust emissions.
Hybrid Synergy Drive System
Components
Unlike parallel or ‘mild’ hybrids, which use
additional electric motor power purely to boost
petrol engine performance, or ‘series’ hybrids,
which rely on electric power alone to drive the
wheels, new Prius is a full hybrid capable of
running in petrol and electric modes alone, as
well as a combination of both.
That means it delivers the
energy-saving benefits of a series hybrid
combined 
with
the performance benefits of a parallel hybrid.
It gives new Prius seamless acceleration and
remarkably quiet operation, while also returning
class-leading fuel efficiency and ultra-low
emissions.
The system comprises a 1.8-litre VVT-i petrol engine, a powerful electric motor, a generator, a high-performance battery, a power control unit and a power split device, which uses a planetary gear set to combine and re-allocate power from the engine, electric motor and generator as required.
The key to the successful installation of Hybrid Synergy Drive within Prius’s front-engine platform is the housing of the electric motor, generator and power split device on a single, lightweight and highly compact transmission casing that is little bigger than a conventional gearbox. The new transaxle itself is smaller, 20kg lighter and benefits from a 10 to 20 per cent reduction in driveshaft energy losses compared to the current system.
1.8-litre VVT-i Atkinson Cycle
Engine
A new four-cylinder, 1.8-litre VVT-i Atkinson
cycle petrol engine replaces the 1.5-litre unit
in current Prius. Generating 97bhp at 5,200rpm
and 142Nm of torque at 4,000rpm, it delivers
higher torque at lower revs – a reduction of
300rpm at 75mph – and combines quieter running
with a 10 per cent improvement in long distance
cruising fuel economy.
Adopting the Atkinson cycle and a new, cooled exhaust gas recirculation system brings significant gains in fuel efficiency and emissions reduction.
80bhp Electric Motor
New Prius has a 80bhp (60kW) electric motor that
works in tandem with the petrol engine to
improve acceleration, and which powers the
driven wheels alone when the vehicle is
operating in EV mode. Compared to the motor used
in the current Prius, it is 20 per cent more
powerful, yet 33 per cent smaller.
During deceleration and under braking, the electric motor acts as a high-output generator to produce regenerative braking. This optimises energy management in the Hybrid Synergy Drive system by recovering kinetic energy that would normally be lost as heat as electrical energy for storage in the high-performance battery.
New Prius’s seamless transmission has three ‘on-demand’ driving modes: EV, ECO and POWER to increase fuel economy, driving efficiency and performance according to driving conditions.
From start-up and at speeds of less than 31mph (50km/h), new Prius automatically operates in EV mode. The driver can also select EV mode manually, with the car’s driving range determined by the level of battery charge.
In ECO mode, throttle response to aggressive accelerator pedal inputs is reduced and the air conditioning control is adjusted for improved fuel economy. Depending on driving conditions, ECO mode can help drivers achieve a 10 to 15 per cent reduction in fuel consumption.
Finally
POWER mode modifies response to throttle inputs,
boosting power to improve acceleration and give
greater driving pleasure.
