A new platform, new engine, new motor and new battery provide the biggest fuel consumption improvement between Prius generations

THIS IS THE next Toyota Prius, and its maker is gunning for an 18 percent improvement in fuel efficiency, from the current model’s already-impressive 4L/100km (or 25km/L). That should help the Prius remain one of the most clean cars in Singapore, and one of the few to score the maximum $30,000 CEVS rebate.

On a wider scale, it should also allow Toyota to keep its crown as the king of hybrid cars. Since 1997, the carmaker has sold more than 8 million hybrids, far more than any other manufacturer. 3.53 million of those have been Priuses.

The improvement to fuel consumption will be the biggest yet between Prius generations. To achieve them, the fourth-generation car is relying on a complete revamp, including a redesigned engine, a new hybrid system and an all-new platform.

The engine will continue to be a 1.8-litre, four-cylinder petrol with VVT-i, but extensive changes mean it will reach 40 percent thermal efficiency — that’s comparable to a diesel, and much better than most petrol engines, which only convert one-third of their fuel energy to forward motion.

Toyota reduced the engine’s internal friction, and redesigned the intake ports and pistons to create more swirl in the cylinders. Exhaust gas recirculation was also increased to boost combustion efficiency.

The electric motor and transmission have also been redesigned to cut weight and size, with new gearsets that reduce friction by 20 percent.

By itself the engine is now good for 98hp (or 72kW) and the electric motor can produce 72hp (53kW). Toyota hasn’t released details about the engine-motor system output, but for comparison the current Prius has 133bhp to draw on in total.

The battery will be a Nickel-Metal Hydride unit— Toyota calls it “the optimum choice to meet market requirements” —although some reports say a Lithium-Ion option will be available, too. Either way, the new battery is more energy dense and now fits under the rear seats.

That frees up boot space, so the fourth-gen Prius has 502 litres back there. That’s a handy 56-litre increase.

And that’s in spite of the new car’s double-wishbone rear suspension, instead of the space-saving (and cheaper) torsion beam in the current model. That should improve its handling, and ensure that it takes bumps more smoothly.

How it feels to drive will have big ramifications for Toyota, too. The new Prius is the first model to be built on the Toyota New Global Architecure (TNGA), the modularised frame that the company will use to build most of its cars from now on.

Using TNGA means the next Prius is 60 percent more rigid, thanks to 19 percent high-strength steel content (up from 3 percent). That should result in a car with more precise handling and steering.

A new hydraulic brake booster will help the braking feel more natural, too, while reducing noise.

There’s also a new adaptive drive mode that monitors the G-forces acting on the car to detect when the driver is in a hurry, and tweaks the engine braking and throttle response accordingly.

The new Prius’ body height is lower by 20mm but Toyota says headroom has improved because the highest point on the roof was moved forward, and the car’s aerodynamics have been tweaked to bring the drag coefficient down to 0.24Cd — marginally better than the current car’s 0.25Cd.

Inside, the interior gets full colour, displays on twin 4.2-inch high-res screens, along with a clever new feature: the air-con system senses which seats are empty, and saves energy by blowing less cool air at them.

Toyota says every seat has been redesigned for better long-distance comfort. That’s something the 1,700 cab drivers who use a Prius here can appreciate.

They’ll have to wait to try for themselves, though. Expect to see the new Prius in Singapore only in 2016 — indeed, full details of the car will only be out when it makes its first public appearance at the Tokyo motor show this month.

And as advanced as the next Prius will be, it remains to be seen how widely its new tech will be embraced here. At the moment, only one in a hundred cars on Singapore roads have petrol-electric propulsion.

CAN’T WAIT TILL 2016 FOR THE SINGAPORE LAUNCH? MORE PICS OF THE NEW PRIUS HERE: