2012 Toyota Prius c: Urban Hybrid

Gary S. Vasilash

Consider a car that is sized for the city and can get an EPA estimated 53 mpg while rolling in the urban environment, a car that doesn’t come equipped with a plug. It’s the Prius c.

The car that was once sniffed at in Detroit as being a “marketing gimmick” went on sale in Japan in 1997, then in the U.S. in 2001. It was the first-generation Toyota Prius. Satoshi Ogiso, a chief ngineer at Toyota Motor Corp., recalls that for the first model—and he recalls with first-hand knowledge, having been assigned in 1993 to the G21 development team, which was the Toyota program that gave rise to the first Prius—the goal was to achieve maximum efficiency. This explains the somewhat awkward high-roofline and boxy design. Still, the car from the point of view of the powertrain—which was also quite efficient—put the Prius on the map in a big way from the standpoint of engineering, both developmental and manufacturing.

Here’s a lesson to be learned that’s of benefit of anyone involved in product development.  Ogiso says that during early days of the Prius, he began to talk with people in the service departments at dealerships. They had extensive first-hand knowledge of what customers disliked (after all, odds are they wouldn’t have been in the service office if they didn’t have something wrong with their vehicles, routine maintenance notwithstanding). People talk about the “voice of the customer.” That’s what he was getting at. Ogiso learned what he could. Among the learnings was that people who were driving what was undoubtedly one of the most—if not the most—technologically sophisticated vehicles on the market, wanted a car that appeared to be more advanced than other cars on the road. So as a result of this, Ogiso conducted a survey of desirable vehicle silhouettes.

Based on what he learned he began to recommend that the second-generation Prius be significantly different in how it looked and what it offered. While he recalls meeting after meeting—let’s face it, Toyota management was taking a huge risk in producing a hybrid vehicle, as only Honda was also in the market with a hybrid at that time, so making radical changes to what was already a radical vehicle was somewhat inconceivable—his emphasis on the voice of the customer paid off. 

But when the second-generation Prius went on sale in October 2003, it was radically different inside and out. Notably, it had the profile that has become visually synonymous with “Prius” ever since. Inside, the car was equipped with a power button to start and stop the vehicle; the gearshift was akin to a joystick from a video game, which was accentuated by the LED gauges. Motor Trend made it the “Car of the Year.” Automobile named it “Design of the Year.” Consumer Reports reported it as the “Most Significant Vehicle of the Year for 2004.” 

Gen three—now known as the Prius Liftback—was launched in 2009 as a 2010 model (autofieldguide.com/articles/2010-prius-the-not-so-little-car-that-can). And in October 2010 Toyota Motor Corp. proudly announced that it had sold more than two million Priuses on a global basis. Six months later, in April 2011, it was announced that one million Priuses had been sold in the U.S. 

Clearly, they had a good thing going. But there was one issue: It was just one model. You could buy a trim package, but essentially a Prius Liftback was a Prius Liftback. 

So Toyota engineers went to work on broadening the portfolio. In January 2011 at the North American International Auto Show in Detroit, Akio Toyoda unveiled the “Prius Family” that was going to be rolled out within the following two years. The first line extension was the Prius v, a larger, wagon-like variant (autofieldguide.com/articles/a-familyprius-for-the-prius-family).

There is a Prius Plug-in (based on the Liftback), offering the ability to drive 15 miles purely on electricity, coming in the second half of 2012.

But now there is the smallest member of the family, the Prius c, for which Satoshi Ogiso is the chief engineer. He’s also the chief engineer for all of the vehicles in the Prius family. Looks like his efforts toward improving the product via the voice of the customer has paid-off vis-à-vis his career.

Looking at the Prius c

The “c” is for city. This is a small car. Toyota considers it a aubcompact. It measures 157.3-in. long, 66.7-in. wide, 56.9-in. high, and has a 100.4-in. wheelbase. However, given its interior volume of 87.4-ft3 for passengers, 17.1-ft3 for cargo), the Prius c is categorized as a compact by the EPA.

The biggest claim to fame for this small car is that with its estimated EPA 53 mpg in the city, it offers the highest fuel efficiency of any vehicle without a plug.

This efficiency is predicated largely on the use of the Hybrid Synergy Drive, the system that Toyota engineers have architected for use in its hybrid
vehicles. In this case there is a 1.5-liter inline four that uses the Atkinson cycle (the intake valve opening events are setup so that there is delayed closure during the compression stroke so a portion of the intake charge is forced back into the intake manifold so that it is used by the next cylinder; this improves thermal efficiency and maximizes fuel use) mated to a new transaxle developed for the Prius c.

This transaxle uses two motors. The 56-hp motor acts as a starter/generator; the 60-hp motor acts as a motor. There are a power split-mechanism, a speedreducer gear set, and an open-type differential. The total system output is 99 hp and 82 lb-ft of torque. There is a 144-v nickel-metal-hydride battery pack located under the rear seat of the vehicle (not behind the rear seatback, which is the case with the Liftback.

The Prius c has an EV mode that allows the vehicle to be driven on electric power. This capability, dependent on the state of charge of the battery, is for speeds under 25 mph and for a distance of one mile or less.

Overall, the goal was to reduce the weight of essentially all aspects of the vehicle. So, for example, the battery pack weighs 67.2 lb. compared to the 91-lb. battery pack in the Prius Liftback (although that is a 201-v pack); the power control unit for the c is 3 lb. lighter (10%). The transaxle is 16% lighter.

Structurally, the vehicle is produced with a variety of steels, including ultrahighstrength grades. The body panels are steel, as well. There is an aluminum rear bumper reinforcement.

The curb weight is 2,496 lb., which is 19% lighter than the Prius Liftback.To reduce parasitic losses, there are both an electric water pump and electric power steering deployed in the c. You don’t get numbers like 53/46/50 city/highway/combined mpg without taking everything into account.

Ogiso says that in order to provide a nimble driving capability (prior to joining G21, he was a chassis engineer, and worked on the last-generation Celica) they made efforts to place the weight low in the vehicle where they could, not only as in the battery pack horizontally below the rear seat rather than parallel to the back of the seat, but even to the extent of lowering the location of the engine by 0.8 in. in the vehicle.

“My goal was to create an attainable compact hybrid that would be fun to drive, have youthful, edgy styling, and not compromise the technologies, fuel economy, and environmental friendliness the Prius was known for,” Ogiso says. It’s worth noting that the MSRP for the base model Prius c is $18,950—which is lower than the MSRP for the firstgeneration Prius 12 years ago.