Toyota, aiming for new showcase, packs Prius with tech
TOKYO -- Toyota is packing the next-generation Prius with such a profusion of new technologies that it makes the best-selling hybrid truly worthy of its name, which means “to go before.”
It starts with a completely re-engineered 1.8-liter engine and two choices of denser batteries that boost fuel economy by at least 10 percent over the outgoing, third-generation vehicle.
Toyota Motor Corp. also promises livelier driving dynamics thanks to a body architecture that is 60 percent more rigid and software updates that provide smooth, more direct acceleration.
Also on tap: An electronic four-wheel drive option.
Indeed, the fourth-generation Prius aims to be a showcase for the brand’s latest powertrain, chassis and safety technologies.
The automaker unveiled the design of the car last month, but offered detailed specifications for the first time today in Japan.
The company did not outline grades or options. But availability of equipment, such as the four-wheel drive system or the new lithium ion battery, will likely vary by market.
Toyota’s U.S. press release, for instance, made no mention of the four-wheel drivetrain highlighted in the global materials.
Among its litany of new offerings:
- An overhauled engine achieving 40 percent thermal efficiency.
- New, denser lithium ion and nickel-metal hydride batteries.
- Active grille shutters to improve heating performance.
- A redesigned, lighter electric motor and transaxle.
- Extensive use of high-tensile steel for a more rigid body.
- Double wishbone rear suspension.
- A sleeker drag coefficient for better aerodynamics.
- Active hydraulic booster for brakes to improve feel.
- New seats to relieve hip strain during long journeys.
- Full color, 4.2-inch high-resolution display screen.
- New color head-up display.
- Toyota’s Safety Sense P pre-crash auto braking system.
"Our target was to ensure that there was significant improvement," Prius Chief Engineer Koji Toyoshima said at a briefing, adding that rival hybrids are crowding a segment pioneered by the Prius and long dominated by the nameplate. "The competition is getting fierce now … We want it to have an edge."
The next-generation Prius builds on the technology around which Toyota has cultivated its reputation as a leader in green cars.
Indeed, since introducing its first hybrid in 1997, Toyota has sold more than 8 million gasoline-electric vehicles globally. The Prius hatchback accounts for 3.53 million of those sales.
More fuel efficient
True to the hybrid’s roots, most of the next-generation’s innovations come in the form of improved efficiencies.
The 10 percent boost in EPA-estimated mpg compares with the 2015 Prius, rated at 51 mpg/city, 48 mpg/highway and 50 mpg combined. But an Eco model of the next Prius is expected to achieve an even bigger improvement, Toyota said.
Certain versions will achieve fuel efficiency of 40 kilometers per liter, as measured under Japan’s domestic testing cycle. That equates to around 94 miles per gallon, but the Japanese figure does not convert directly into an EPA rating because the testing cycle is considered less stringent that the EPA’s.
Toyota did not disclose an expected EPA rating.
The 40 percent thermal efficiency edges the 38.5 percent in the current Prius. Higher efficiency means more energy from internal combustion is captured to power the wheels and less is lost through heat.
Toyota said the new Prius engine has the world’s highest thermal efficiency in any mass-produced gasoline engine.
Toyota achieved the improvement partly through a large-volume exhaust gas recirculation system and redesigned air circulation through the combustion and cooling chambers.
Engineers also cut friction on moving parts such as piston skirts and the oil pump. The active grille shutters open and close the grille as necessary in response to outside temperatures. They also improve aerodynamics.
In fact, the overall design of the Prius delivers a slick 0.24 drag coefficient for cleaner airflow around the body. That too beats the outgoing version’s already impressive 0.25 figure.
The redesigned motor and transaxle achieve a 20 percent reduction in mechanical loss through friction. The outgoing version’s planetary arrangement in the reduction gear has been replaced with parallel gears to further reduce loss.
The engine delivers a maximum output of 72 kilowatts, while the motor chips in another 53 kilowatts for total power of 125 kilowatts. Toyota did not provide a net horsepower figure.
That compares with about 73 kilowatts for the current engine and about 60 kilowatts for the current motor. The combined net hybrid powertrain output of the third generation is 134hp.
Toyota says it is offering new lithium ion or new nickel metal hydride batteries. The outgoing version uses only nickel metal hydride batteries. Toyota says the new batteries use the same basic technology but have higher energy density.
Toyota did not disclose the energy output of the batteries, but the lithium ion battery and nickel-metal hydride alternative deliver roughly the same output, battery engineer Takanori Kumagai said. The main difference is weight: The lithium battery weighs 24.5 kilograms (54 pounds), compared with to the nickel-metal’s 40.3 kilograms (89 pounds).
But the higher energy density allows Toyota to pack more energy in smaller battery modules. And because the batteries are smaller, they can be placed under the rear seats.
This opens more cargo space in the rear.
Even inside the cabin, Toyota targeted better efficiency.
A smart-flow air conditioning system saves energy by detecting whether the front and rear passenger seats are occupied and cuts down on waste by reducing airflow to empty seats.
And despite the fact that the next Prius is 20 millimeters (0.8 inch) lower than the current version, a tweaked roof design actually delivers more headroom for passengers.
That is achieved partly by moving the high point of the roof 170 millimeters (6.7 inches) forward.
Total luggage capacity grew by 56 liters, to 502 liters.
The Prius is also the first Toyota vehicle to get the company’s new modularized platform structure, dubbed Toyota New Global Architecture, or TNGA. It boosts body rigidity by more than 60 percent through the use of laser screw welding, body adhesives and a new frame design. Engineers increased the ratio of high tensile use to 19 percent, from 3 percent in the outgoing car.
The stiffer body helps suppress vibration and noise. But so does extensive insulation added to the floor and engine compartment to dampen road noise and deliver a quieter cabin.
For sportier handling, Toyota also splurged on a double wishbone rear suspension, a more costly and sophisticated setup than the rear torsion beam in the outgoing Prius.
The driver’s hip point has been lowered by 59 millimeters (2.3 inches) to optimize the driving position.
The new Prius will also get a four-wheel drive option for the first time. Dubbed E-Four, the system will be powered by a high-output rear motor, which assists the engine and front motor to deliver power to both sets of wheels.
Thanks to its compact size and lightweight design, it minimizes impact on overall fuel economy and still allows for comfortable legroom, Toyota said. Luggage space is the same as in the two-wheel drive version, with a spare tire, the company said.
Toyota, which is playing catch up in rolling out advanced driver-assist safety features, is also loading the Prius with its latest pre-crash automatic braking system, Toyota Safety Sense P. It includes a function for pedestrian recognition.
The system, the higher grade of Toyota’s two Safety Sense packages, uses millimeter-wave radar and a single-lens camera that can detect both cars and pedestrians.
In Japan, at least, the Prius will be Toyota’s second vehicle to get the company’s new vehicle-to-infrastructure intelligent transport system, called ITS Connect. It enables vehicles to talk to each other, scans blind spots, warns of changing traffic signal and helps keep a safe distance from other cars.
Finally, the next Prius will also get Intelligent Parking Assist. This feature uses ultrasonic sensors to detect surrounding objects and identify parking spots, while also helping the driver slip the car into tight spaces.