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Future for Powertrains


Global vehicle population is growing at a faster rate than world population, from about 720 million units today to a little over 1.1 billion vehicles projected in 2020, according to Edward P. Becker of General Motors Powertrain Division. And while internal combustion engines that use conventional fuels and lubricants wont disappear overnight, drivers are seeing a greater array of propulsion technologies to choose from.

In a January webinar sponsored by the Society of Tribologists and Lubrication Engineers, Becker, who holds a Ph.D. in mechanical engineering from the University of Michigan, described the splintering variety of new automotive technologies as well as their benefits and issues.

Currently, Becker pointed out, world population is about six billion people, while vehicles of all type represent about 12 percent of that number (or about 720 million units). Over the next 10 years, world population is expected to shoot past seven billion, and vehicle population will reach 16 percent of that figure, or just over 1.1 billion vehicles on the planet.

The relationship between per capita income and number of vehicles per 1,000 population is significant, added Becker, a licensed professional engineer and past president of STLE. The higher the per capita income of a country, the more vehicles per 1,000 people.

Interestingly, this ratio tends to peak at about 800 vehicles/1,000 population when average income reaches the $30,000 to $35,000 mark, he said. The United States and Japan are in that position already, and others are still climbing the prosperity ladder to a greater or lesser extent. The obvious implication is that developing countries will see growth in their vehicle populations, while the more developed nations settle into a stable replacement mode.

Turning to engine design, Becker noted that over the last 35 years or so, engine design has gone through growth of horsepower and displacement, with a sharp decline in the energy-sensitive early 1980s, and then a continuation of the horsepower gains – but without the growth in displacement. This is the result of government intervention to improve fuel economy and minimize emissions. Due to these mandates, engine efficiency has steadily increased, as measured by the ratio of horsepower to displacement (HP per cubic inch). In 1975 an output of about 0.5 HP/ of displacement was typical. By 2005, this had passed 1 HP/, and new engines currently get about 1.15 HP.

There were a number of innovations in engine and vehicle drivetrain design over that time, continued Becker. However, the impact of most innovations usually is not felt for about 15 to 20 years. Theres a very consistent time lag between when a technology is introduced and when it reaches its maximum penetration in the market, he observed.

For example: American-made, front-wheel-drive vehicles debuted around 1980, but after five years, only 20 percent of vehicles sold were front-wheel drive. It wasnt until about 1995 that market penetration reached more than 80 percent of production. Today, primarily SUVs and pickup trucks still retain rear-wheel-drive powertrains.

Variable valve timing, port fuel injection and multi-valve engine designs are further examples of technologies that gradually penetrated the marketplace, Becker said. New technologies being studied include more advances in variable valve timing (including lift and duration), cylinder deactivation, direct gasoline injection, six- and seven-speed transmissions, continuously variable transmissions and hybrid engines. Each of these innovations promises better fuel economy and performance.

The technology thats been getting an awful lot of press is the hybrid powertrain, Becker continued. This is a combination of an internal combustion engine, either gasoline or diesel, with an electric motor.

GM, he pointed out, has chosen to focus on larger hybrid vehicles, such as SUVs and pickups, as opposed to the smaller vehicle mix of other automakers, because SUVs offer greater potential fuel savings than small passenger cars. As well, GM has a significant presence in the larger vehicle market so it is anxious to protect and even enhance that area. For 2011, the company is offering five hybrid configurations – three SUVs and two pickups – in its Chevrolet, Cadillac and GMC lines.

At the upper end of the power scale, GMs Allison Transmission segment has developed a hybrid bus for commercial use and has more than 600 of these in service worldwide, including Seattle municipal buses and shuttles used in Yosemite National Park. These 600 buses save as much fuel as 34,000 gasoline hybrids, Becker stated.

All-electric vehicles also have a great future, he went on. In the early days of the automobile, electric-powered vehicles were considered a very formidable challenge to internal combustion engines. Only when internal starters on engines replaced hand cranks did the economy of the internal combustion engine outweigh the convenience of electric power.

The latest electric vehicles such as the Nissan Leaf offer ranges of about 100 miles on a four-to-six-hour battery recharge, Becker noted. For many, that is sufficient for daily use since most commutes are less than 20 miles one way. However, as the vehicle approaches its range limitation, a phenomenon called range anxiety overtakes the owner. Consumers are used to the 350-plus mile range of most internal combustion engines, and want the same from electrics. All-electric vehicles cannot deliver such distances at present, Becker said, and some breakthrough in battery technology will be needed to achieve this goal.

General Motors own entry in this field is the 2011 Chevrolet Volt, an electric car with a small gasoline engine aboard to drive a recharging system. The Volt can go about 40 miles on its fully charged battery alone, Becker pointed out, but when the battery charge drops to a low level, the engine engages and runs a generator to recharge the battery. That pushes the range to about 360 miles in all, and does not eliminate the need for engine oil: According to the owners manual, the Volt needs 3.7 quarts.

There remain a lot of unknowns about electric vehicles, Becker indicated – battery life and replacement cost among them. This led him to predict that in the 2020 to 2030 time frame, all-electric vehicles will still be a niche product.

Faster growth will be seen in alternative-fuel or flex-fuel vehicles, he indicated. Flex-fuel vehicles can use gasoline-ethanol blends up to 85 percent ethanol, well beyond the 10 percent ethanol blends currently used in the United States. GM has 23 models with flex-fuel capability available now, and plans to have the option available for 50 percent of its new units for 2012.

Another alternative fuel available is compressed natural gas or liquefied natural gas. Conversion kits have been sold for a number of years which allow a gasoline-fueled engine to run on gaseous fuels, and GM has this fuel option available on its Chevrolet Silverado/GMC Sierra pickup truck line, Becker added.

The ultimate alternative fuel is hydrogen, which is not as dangerous as many believe, Becker said, even though the Hindenburg disaster of 1937 continues to cloud hydrogens prospects. Being a gas, he noted, hydrogen burns upward, not outward as does gasoline or other liquid fuels. Presumably, ground vehicles would not face the same falling-from-the-sky risk that the ill-fated dirigible encountered.

Hydrogen fueled engines would be emissions-free since the combination of hydrogen and oxygen would produce only water as exhaust, he said, and would be a great addition to the automotive product mix. He pointed out that former California governor Arnold Schwarzenegger had his own Hummer converted to hydrogen power, which shows it is possible to build the vehicles. They consume around 10 kilograms of hydrogen for a 300-mile range, too, so range anxiety would probably not be a major concern.

The biggest drawback is the lack of a distribution system to supply hydrogen to the driving public. Given the rule of thumb that it takes 20 years to fully incorporate such technology into the general marketplace, we might expect to see hydrogen-fueled vehicles on the road in quantity by 2030, Becker added.

Another and better use for hydrogen may be fuel cells, he said. What the GM engineers did is they asked themselves the question, If we were designing a hydrogen fuel celled vehicle from the ground up and we didnt have 100 years of vehicle design behind us, what would it look like? The answer was GMs Autonomy concept car, powered by a hydrogen fuel cell and having a projected range of 300 miles using about 5 kg of hydrogen. That makes it twice as efficient as the hydrogen-burning engine. But the uniqueness of the Autonomy doesnt stop with a fuel cell power plant.

The Autonomy is designed so that all of the running gear, powerplant and fuel are confined in a chassis that is about 14 inches high. The body and passenger compartment occupy a separate unit which attaches to the chassis. This makes it possible for drivers to attach more than one kind of body to the same chassis – a passenger car body for daily use, a pickup body for special hauling projects, a mini-van body to take the soccer team to its game, and even a two-seater body for some high performance fun on the road. The garage may be crowded but will only have to house one powerplant.

On the subject of automotive lubricants, Becker foresaw little change ahead in the shape and direction for internal combustion engine oils. Fuel economy, durability and improved emissions performance will continue to drive engine oil development and standards. Ethanol could have an impact, but only if blend levels in gasoline increase substantially. Older engines in particular could feel this impact.

Automatic transmission fluids will continue to evolve, with the emphasis on newer transmission designs and as a lubricant for the electric motors, said Becker. Chassis lubrication will remain the same.

The fuel mix, however, seems destined to be more diverse. The challenge will be to make sure that the vehicles out there are capable of running on the fuels that are available, he emphasized. The average vehicle in the U.S. now is 11 years old. Its a matter of developing confidence in the consumer, that when they buy a vehicle that runs on a particular fuel, that fuel is going to be available in quantity, not just today but in a decade from now as well.

Which of the future propulsion systems will be successful in the end? Beckers answer was succinct: Economics and availability will determine the winner.

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