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When the 2016 Toyota Prius was unveiled last month, we saw in full the bold, avant-garde styling, but little in the way of actual specifications regarding the revamped powertrain. That time has come, with Japan’s largest carmaker posting more details about what moves the fourth generation of its iconic hybrid.

Firstly, there’s the internal combustion engine (ICE) – the current 2ZR-FXE 1.8 litre Atkinson-cycle VVT-i petrol four-pot has been retained, but is now completely reengineered. Power and torque remain near-identical – the former is actually a horsepower down, so the figures stand at 97 hp and 142 Nm. However, peak torque is now made 400 rpm lower in the rev range, at 3,600 rpm.

But the main improvements come in terms of thermal efficiency. As previously reported, the engine is now the world’s most efficient mass-produced ICE – with a maximum figure of 40% – thanks to a large-volume exhaust gas recirculation (EGR) system, a redesigned air intake port that improve combustion chamber airflow, revised coolant passages to optimise internal engine temperature and improvements in combustion efficiency. Internal friction has also been reduced, thanks to, among others, the use of low-viscosity oil.

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The two all-new electric motors are, strangely enough, also less powerful than the ones that came before. Power is now at 53 kW (71 hp) instead of 60 kW (80 hp) previously, while torque has decreased from 207 Nm to 163 Nm. It’s no wonder that Toyota has yet to release the total system power output figure, as it’s bound to be lower than the current 134 hp.

Despite the reduced output, both motors actually boast higher output densities, being smaller and lighter than before and incorporating a rolling-coil structure. The size and weight of other key components, such as the transaxle, power control unit and batteries, have also been reduced – improving fuel and space efficiency.

The power control unit, in particular, has been upgraded – including the use of low-loss components – to deliver 20% lower electrical losses, with a more compact design enabling it to sit directly above the transaxle. Speaking of which, the latter also possesses 20% fewer losses thanks to the motors’ multi-shaft positioning, as well as the relocation of the final drive reduction gear onto the same axis as the drive motor.

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Depending on where you live, the Prius will be offered with either nickel-metal hydride or lithium-ion batteries, both positioned under the rear seats. The relocation of the auxiliary battery to the engine bay from the boot floor increases cargo space by 52 litres to 502 litres, despite the rear deck now 55 mm lower than before. For the first time, the Prius will also be offered in E-Four guise, with a high-output rear electric motor providing four-wheel drive – without compromising boot capacity.

Fuel efficiency is improved further through the use of an automatic grille shutter (drag coefficient now down to 0.24 Cd), an improved and more compact exhaust heat recirculation system, an engine coolant selector valve and a new system that accelerates engine heating. Altogether, the Prius is targeted to achieve a fuel consumption figure of 40 km per litre on the JC08 cycle, up from 32.6 km per litre of its predecessor.

Under the skin, the Prius is the first car to ride on the modular Toyota New Global Architecture (TNGA), designed to lower the centre of gravity. Torsional rigidity is up 60% due to the use of laser screw welding, structural body adhesives and ring-shaped frame structures. High-tensile-strength steel content, utilising hot-stamped materials, has also been increased from 3% on the previous model to 19%

In conjunction with the new double wishbone rear suspension (which replaces the previous torsion beam setup), the increased rigidity not only improves handling, but is also claimed to deliver a firm, stable ride, as well as lower NVH – this can be felt, Toyota says, from the windows and doors down to less obvious areas such as the floor and ceiling.

Elsewhere, there are revisions to the hybrid system software to improve acceleration feel, an adaptive system in Power mode that engages a sportier acceleration and deceleration setting during enthusiastic driving, as well as a new active hydraulic booster for regenerative braking to improve brake feel and reduce noise.

Other measures to improve comfort include lighter and more space-efficient front seats with upgraded frames and cushioning to provide a snug fit and chiropractic control, repositioned back springs for improved posture as well as a 59 mm lower hip point that provide a more natural and comfortable seating position. At the back, there’s improved cushioning and a wider seating area, and while the roofline is lower than before, Toyota claims headroom has actually increased over the old car.

More improvements abound inside – the digital instrument cluster has been redesigned with two 4.2 inch full-colour TFT LCD screens – multi-info display on the left, basic vehicle data on the right. There’s also a Toyota-first full-colour head-up display (HUD) projected directly to the windscreen, a temperature-regulating synthetic leather steering wheel, as well as an S-flow air-conditioning system that focuses airflow only at where the occupants are seated, to maximise comfort and fuel economy.

Active safety features include the Toyota Safety Sense P suite with Pre-Collision System, Lane Departure Alert, Automatic High Beam and Radar Cruise Control, an Intelligent Clearance Sonar (ICS) that prevents collisions resulting from low-speed pedal misapplication, Simple Intelligent Parking Assist, a Blind Spot Monitor as well as the new Japan-only ITS Connect vehicle-to-infrastructure (V2I) and vehicle-to-vehicle (V2V) communication service, first fitted to the facelifted Crown range.

Oh, and remember the lurid green heat-reflective paint we reported a few weeks ago? Toyota has finally revealed what it is – a Thermo-Tec Lime Green paint option exclusive for the Japanese market, that helps “mitigate increases in exterior surface temperature.”