2010 Prius chief engineer Akihiko Otsuka and his car. Otsuka said that they spent 4.5 years—“and countless man-hours”—developing the third-generation car that has become synonymous with “hybrid.” More than 2,000 engineers were involved in the development, and he had 100 team leaders reporting to him during the vehicle’s development.
The 2010 Prius had more hours in the wind tunnel than any other Toyota vehicle. Note the flat sides of the fender flares and the edges of the bumper.
On the left is the transaxle for the second-generation Prius; the third-generation model is on the right. Notice that the new one is more compact and that the chain drive has been replaced by the gear drive.
Akihiko Otsuka said that all things considered, it is rather unexpected. With a bachelor's in electrical engineering, he joined Toyota Motor Corp. (TMC) in 1986 in the Noise and Vibration Development Div. There, he had the opportunity to work on cars including the Supra, Celica, and Carina. (As you may recall, the Supra and the Celica were once available in the U.S. No more.) As time passed, he was moved to Europe, where he worked on testing and tuning vehicles for that market. He returned to Japan in 1998 and worked in the Product Planning department, where he became the assistant chief engineer for the Prius and Estima Hybrid. In 2007, he was made chief engineer for Prius. Which, as he said, is something that he never expected. Otsuka said that he spent four-and-a-half years working on the Prius. One thing about that time. Otsuka joked that "TMC" has another meaning other than the official acronym: "Toyota Meeting Corporation." Apparently, you don't develop the third-generation of the world's leading hybrid car without having lots of meetings.
One thing that is somewhat amusing about the discussion of the 2010 Prius: the issue of "performance" comes up, not in the context of fuel efficiency (although is certainly part of the discourse, and a very large part of it), but vis-à-vis 0-to-60 mph time. While no one is going to confuse it for, say, the aforementioned Supra, as it is a vehicle with a net horsepower (i.e., combining the internal combustion engine and the motor generator) of 134 hp, the rated time is 9.8 seconds, or a speed improvement of 1.1 seconds compared with the second generation. The top speed is up 9 mph, to 112 mph. All things considered, that's not bad. But the fuel efficiency is good. Really good.
A combined 50 mpg. Forty-eight highway. Fifty-one city. If there is one thing that is completely characteristic of Toyota, it is that continuous improvement is the way of work. So consider: the first-generation Prius (available in Japan in 1997; in the U.S. in 2000) provided a combined EPA fuel-efficiency number of 41 mpg. The second-generation Prius, which went on sale in 2004, has a number of 46 mpg, combined. And now it is 50.
Odd, Isn't It?
While much of what makes the 2010 Prius more efficient comes down to shrinking things-the transaxle is lighter than the previous model (but torque losses are reduced by up to 20%); the inverter has a direct cooling system, which makes it smaller than its predecessor-oddly enough, the internal combustion engine used is actually bigger and more powerful than that used in its predecessor. There is a 1.5-liter, 78-hp four under the hood of the second-gen Prius. The third-gen has a 1.8-liter Atkinson-cycle four that produces 98 hp at 5,200 rpm. Overall, the combined net horsepower of 134 is an improvement from the 110 hp of the second-generation model. Which might seem counterintuitive.
So are a couple other things that are available for the car. One is a sliding-glass moonroof. Nothing particularly odd there. But what is out of the ordinary are the solar panels packaged within the roof. The power generated by these panels is used to power a fan that cools the interior of the car. The solar panels don't put electricity into the battery. They run the fan. The benefit is said to be of making the cool-down of the vehicle shorter, thereby reducing the amount of air conditioning required at start up.
But in the realm of air con, there is something that is certainly out of the norm: On the smart fob (for cars so equipped; it is part of the solar powered ventilation system package) there is a button that allows remote start not of the car, but of the air conditioner. In this case, the car's air conditioner will run for up to three minutes, drawing energy from the nickel-metal hydride (NiMH) battery pack (assuming that the controller determines that there is sufficient charge in the battery). Bill Reinert, Toyota's national manager, Advanced Product Technology, explains that the calculations show that by doing this pre-cool of the cabin there is actually less energy used than would be the case if the air conditioner compressor was put under full load upon ignition.
From a design point of view, the third-generation Prius looks pretty much like the second-generation Prius. (Does anyone want to remember what the first-generation Prius looks like?) Doug Coleman, Prius product manager, says that when they surveyed customers-and they're calculating that there will be plenty of Prius owners who will continue to be Prius owners (there are some 700,000 Priuses rolling around in the U.S. at the moment)-and asked what they were interested in the new one having, they said, "Don't change the roof line but add more character." Thus, while there is a greater amount of wedge and a more definite beltline, the 2010 Prius resembles its immediate predecessor. However, it should be noted that the new Prius is more aerodynamic, having spent more time in a wind tunnel than any other car in Toyota's history. The coefficient of drag for the '10 is 0.25, an improvement of 0.01. Of course, this is not just about the exterior sheet metal, although modifications were made to the upper grille opening, the front below the bumper, sharper corners and flat surfaces on the wheel flairs, and a larger grille opening. There is the extensive use of covers beneath the car, including a fin near the back that helps guide the air.
Bigger in Back.
The new Prius is essentially the same size as its predecessor, although it is based on the Toyota MC platform, which is used for vehicles including the current Camry. Looking at the third-generation's dimensions compared to the second's: the 106.3-in. wheelbase is unchanged; the 175.6-in. overall length is up just 0.6 in.; the 68.7-in. width is a 0.79-in. increase; and the 58.7-in. height is the same. Inside, however, there is more room, with the EPA passenger volume going from 96.2-ft3 in the '09 to 93.7-ft3 in the '10. Particular focus was placed on providing more room for the rear seat, by doing such things as making the front seat back 1.38-in. thinner and by reducing the front seat headroom by 0.3 in. and increasing the rear headroom by the same amount.
Although Otsuka and his team worked hard at minimizing the weight of the vehicle-for example, the drive train for the '10 is 20% lighter than in the previous model, which is largely the result of a smaller motor and inverter-the overall car actually weighs slightly more: 3,042 lb., up from 2,932 lb. Otsuka said that much of the additional mass is accounted for in the structure of the vehicle for purposes of safety (although it should be noted that high-tensile strength steel is used in the rocker inner, B-pillar and roof reinforcement, so care was taken to minimize mass while providing strength for security).
Then there is the available technology. A new version of the parking assist that debuted on the Lexus LS 460-a simplified version. There is dynamic radar cruise control. There is a lane departure warning system (a camera looks at the lane markers and if it detects a drift sounds a buzzer and a slight inward torque to the steering wheel). And there is "lane keep assist," a system that is debuting on the Prius: it uses the lane recognition camera and integrates with the electronic power steering system such that when in cruise control, it actually makes slight steering torque adjustments to reduce driver input (i.e., those slight adjustments that you need to make to keep a car going straight), although it does perform a steering wheel torque check to make sure that the driver has hands on the wheel.
When the Prius first appeared, some dismissed it as a marketing gimmick. At the Tsutsumi Plant in Toyota City and the Toyota Auto Body plant in Aichi, Japan, work is underway, building cars for consumers in 80 different countries. Bob Carter, group vp and general manager of Toyota Motor Sales, U.S.A., anticipates 2010 Prius sales of 180,000 for its first full calendar year, and he's factoring in (1) the current economic conditions and (2) the new Honda Insight (see AD&P, February '09 Insight: Honda's Hybrid Puzzle). Clearly, what may have started out as something of a quizzical little car with seemingly limited appeal has turned into a model that has appeal far greater than many mainstream cars.
To learn about the first-generation Prius, see:
Prius: A Look at Toyota's Hybrid
And to learn about the second:
The Toyota Prius: The Most Important '04 Model? Yes.
Toyota and its Lexus brand are more than marginally committed to hybrid technology, as you can see in:
A Lexus Like No Other But Like The Rest
The Lexus LS 600H L: Not Just Another Production Car
Management Lessons of the'07 Toyota Camry
Introducing The 2007 Lexus ES 350 The Car From The "King of Kaizen"