New Toyota Prius: The inside story

Published Oct 13, 2015

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By Dave Abrahams

Las Vegas, Nevada - Toyota's Prius enjoys a high profile amongst America's eco and image-conscious 'greenies', including Cameron Diaz, Matt Damon, Salma Hayek, Harrison Ford, Tom Hanks and even Miley Cyrus.

So it's not surprising that the fourth generation of 'the original hybrid' was given its world premiere in the glitz capital of the world.

Nevertheless, Toyota's mission is to penetrate new markets with what it claims is a completely redesigned Prius, featuring a re-engineered 1.8-litre Atkinson-cycle petrol engine, a more compact electric drivetrain and smaller, more energy-dense batteries that have been moved from under the floor of the boot to under the rear seat - improving both weight distribution and luggage capacity.

Yes, batteries: the Prius will be available with a choice of either nickel metal hydride or more expensive but higher-capacity lithium ion amp-holders.

The maker claims that, under ideal conditions, the petrol engine converts a remarkable 40 percent of the heat generated by combustion into power at the crankshaft, by improving gas flow and reducing losses to internal friction.

The intake ports have been re-shaped to improve gas-flow (and thus clean, efficient combustion) inside the cylinder head, while a large-volume exhaust gas recirculation system reduces pumping losses. The engine runs a special low-viscosity oil, and piston skirts, bearings and even the oil-pump have also been revised to reduce friction.

The coolant passages in the head and block have been redesigned to keep the engine temperature close to optimum, and an active grille shutter has been added to open and close the grille as necessary in response to ambient temperatures.

A revised, more compact exhaust heat recirculation system helps warm up the engine quickly from cold, controlled by a new engine coolant selector valve - a complicated electronic device that serves the same function as the bi-metal thermostat in a 1960s engine.

ADDING LIGHTNESS

The electric motor and transaxle have been re-engineered with parallel gears in place of the previous planetary gears, reducing friction losses by as much as 20 percent.

The electric motor is also lighter and more compact, as is its power control unit, which is now mounted directly on top of the transaxle, reducing power losses in the high-voltage cables by about 20 percent.

Updated hybrid-system software makes acceleration from low revs smoother and more linear, and a new active hydraulic booster makes the regenerative braking system feel more like conventional brakes while also reducing noise.

Anybody who has ever created an origami will know that folding a crease into any material makes it much stiffer. Toyota has used this principle, along with laser screw welding, structural adhesives and a more than six-fold increase in the percentage of high-tensile strength steel - from 3 to 19 percent - to make the Prius 4.0 body-shell 60 percent stiffer than its predecessor.

That improves handling and steering precision, as does the all-new double-wishbone rear suspension, which was made possible by the relocation of the battery pack further forward.

The new body retains the Prius' signature triangular profile, but overall height has been reduced by 20mm and the high point has been moved forward 170mm, increasing headroom for front-seat occupants and improving aerodynamics.

The more compact hardware under the bonnet has also allowed its front edge to be lowered by 70mm and the rear, at the bottom of the windshield by 62mm, improving the driver's forward view.

EUROCENTRIC

After many years of using separate projectors for low and high-beam headlights, the new Prius has bi-LED headlight clusters that use one lens for both beams, giving the front end of the car an uncomplicated Eurocentric look.

Inside, the slim, minimalist instrument panel has white accents on the steering wheel and front console tray for a futuristic look, while the seats have been redesigned with different thicknesses and densities of padding to take the stain off your hips and make long journeys more comfortable.

The same applies to the rear seats, while a clever head-lining design increases rear headroom despite the fact that the rear roofline is actually lower than on the previous Prius.

The multi-information display in the nstrument panel is now presented in high-resolution colour on two 4.2-inch multi-information screens - speed, fuel level and other basic data on the right and a scrollable (using a control on the steering wheel) page of ancillary information on the left.

The essentials - plus navigation alerts such as speed limit changes and important intersections - are also shown in a head-up on the lower section of the windshield.

A new aircon system called Smart-flow detects which seats are occupied and adjusts ventilation and cooling accordingly, minimising airflow around empty seats and thus saving energy.

Also available for the new Prius will be the Safety Sense package, including a pre-collision system with pedestrian detection, and adaptive cruise control, as well an automatic parking system.

Toyota SA says the new Prius will “in all likelihood” be released in South Africa during the second quarter of 2016, but this is still to be confirmed.

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