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Fuel-saving solutions

These days it seems everyone, from suburbanite to farmer, wants a pickup truck or an SUV — $50-a-barrel oil and $2 gasoline be damned. The trend has been a boon to American and foreign truck manufacturers, but it also puts truck-making companies in a bit of a pickle. The more trucks and SUVs they sell, the more difficult it is to meet the government's corporate average fuel economy (CAFE) standards for fuel efficiency and still build the types of vehicles their customers demand.

Successful truck sales are a problem for manufacturers because of the Energy Policy Conservation Act (EPCA), a relic of the 1970s energy crisis. Enacted into law by Congress in 1975, it established CAFE standards for passenger cars and light trucks. The stated near-term goal was to double new-car fuel economy by model year 1985. Today, passenger cars manufactured for sale in the United States are supposed to meet CAFE standards of 27.5 mpg. For light trucks (including vans and sport utility vehicles), the 2004 CAFE standard is 20.7 mpg.

Meanwhile, environmental groups are pressuring Congress to close what they call “the light truck loophole.” The Alliance to Save Energy argues that when CAFE was established in 1975, SUVs, minivans and pickup trucks were allowed to meet a lower fuel economy standard because they constituted only 20% of the vehicle market and were used primarily as work vehicles. But today light trucks are widely used as passenger vehicles and comprise more than half of new vehicle sales.

If you have checked miles-per-gallon ratings on new vehicles, you probably have noticed that a lot of them don't even come close to meeting today's CAFE standards. This is possible because the CAFE standards are applied on a fleet-wide basis for each manufacturer. Manufacturers earn “credits” for each vehicle that exceeds CAFE standards, and these credits can be used to offset fuel economy shortfalls in the three previous and/or three subsequent model years. Manufacturers have relied largely on high-mileage “econobox” models to earn those credits and atone for the sins of their top-selling gas guzzlers.

Industrywide total fleet fuel economy peaked in 1987 at 26.2 mpg when light trucks made up a mere 28.1% of the market. By 2001, with light trucks making up 46.7% of the market, total fleet fuel economy fell to 24.4 mpg. Subsequently, manufacturers are faced with tens of millions of dollars in fines.

Developing and selling a high-mileage roller skate might make for good public relations, but a few thousand tiny 40-mpg hybrid electric passenger cars won't make much of a dent in overall fleet fuel economy when more than half the vehicles a company sells are either trucks or SUVs. Toyota, General Motors and Dodge in particular have realized that they can make the biggest gains toward meeting CAFE standards by focusing on their biggest problem — the fuel economy of their full-size trucks and SUVs. The solution, they hope, lies in developing new fuel-saving technologies.

Cylinder deactivation

Cylinder deactivation, called displacement on demand (DOD) by General Motors, promises one engine that is a V-8 when you need power and a fuel-efficient four-banger during moderate driving. The first vehicles to get GM's new DOD 5.3-l V-8 engine will be SUVs in 2005 and then pickup trucks in subsequent model years. In the first vehicles, the all-aluminum V-8 will be rated at an estimated 290 hp and 325 lbs. ft. of torque and will offer towing capacities comparable to the previous 5.3-l small-block engine. With DOD engineered into this engine, GM promises fuel economy as well as seamless throttle response, power and towing capability. Three vehicles — the 2005 Chevy TrailBlazer EXT, the GMC Envoy XL and GMC Envoy XUV — will be the first to offer the engine in 2005.

However, DOD does have some credibility hurdles to overcome. The first attempt at cylinder deactivation was with the Cadillac 8-6-4 engine in the 1980s. Though it got better fuel economy, the Caddy engine was plagued with strange vibrations, noises, inconsistent performance and poor reliability. But GM says DOD is different this time and two decades of new technology and engineering have solved those old problems.

Marvel of innovation

The new DOD system is a marvel of electronic and mechanical innovation. When the engine is in four-cylinder mode, a computer disables both the intake and exhaust valves of four completely sealed, deactivated cylinders.

Sounds simple, but the Rube Goldberg machine complexity of the system becomes apparent when engineers try to explain how it works. Valves are disabled through a device called a switching lifter. This differs from a normal lifter in that there is an inner body and an outer body connected by a spring-loaded pin. For V-8 operation, the pin is fully expanded by the spring so the two pieces act as one and the lifter acts like a regular lifter.

To disable valve operation, high-pressure oil is delivered to a groove in the lifter that leads to the outside end of the pin, forcing the pin to collapse the spring. That leaves the two parts of the lifter free to move relative to one another. As the cam lobe pushes on the follower, the inner portion of the lifter pushes against another spring at the top of the lifter and does not transfer force to the pushrod.

And that's just a rudimentary explanation; no wonder it took GM engineers 20 years to get it right.

Imperceptible transition

GM says the key component that makes all this complexity work smoothly is a better computer for the electronic throttle control. As the driver presses the gas pedal, the transition from four to eight cylinders and back again is imperceptible. The computer determines when operating conditions are met to enable DOD and monitors engine vacuum as an indicator of customer power demand. When the computer decides to disable four cylinders, it calculates where the throttle needs to go so the torque will be equal during the transition. The driver doesn't feel a change under his foot or a hesitation in engine power. The computer closes or opens the throttle without the driver knowing it.

GM says DOD delivers fuel economy improvements of 6 to 8% on average and up to 20% better for certain driving conditions. When the technology becomes available on pickup trucks, it should be especially useful for farmers, who are required to use their trucks alternately as long-range commuter vehicles and heavy-duty towing machines. GM says the most dramatic fuel savings will be realized during steady-speed driving under 70 mph — just what you'd expect to encounter on a rural highway or country road.

Gas/Electric hybrid systems

No, you don't have to plug it in to charge it up. The vehicle recharges itself. You might even plug your power tools into the vehicle at a work site. Hybrid electric vehicles use a combination of an internal combustion engine, a massive battery bank and one or more high-torque electric motors to turn the wheels. The concept, while fairly recent for automobiles and trucks, has been around in diesel locomotives for years.

Hybrid synergy

A different kind of hybrid electric system from Toyota, called the Hybrid Synergy Drive, drives the wheels of an automobile or truck through a power-split device that couples a gasoline engine, electric motor and battery-charging generator. A computer determines when it is most efficient to power the car directly from the gasoline engine or from the electric motor. Generally, the electric motor kicks in during acceleration or when high-torque is needed. The gas engine drives the wheels at cruising speeds.

The Toyota Prius economy car already uses a Hybrid Synergy Drive. But Toyota has plans for upsizing the system in its SUVs and trucks, including a new version of the Tundra pickup truck fashioned after its recently introduced FTX concept truck. The truck will be produced in a new Toyota plant in San Antonio, TX, which is scheduled to open in mid 2006. The first FTX-inspired Tundras should be ready for the 2007 model year. Although engine details are still secret, Toyota says the FTX uses a large-displacement V-8 in a Hybrid Synergy Drive configuration, so expect lots of torque to go along with the aggressive FTX body panel styling.

Greater fuel efficiency

General Motors also will offer full-size hybrid electric SUVs and pickups, some in 2005 and more in 2007. GM says that, combined with its DOD cylinder deactivation technology, the technology will achieve a fuel economy improvement of about 30%.

One of Dodge's first hybrid electric vehicles was a full-sized Ram pickup introduced in 2000. The hybrid Ram is being sold in 2004 and 2005 with a 110/120v AC electric motor that provides additional power in certain driving situations. Dodge says the hybrid system could boost fuel efficiency by 15% compared to a conventional Ram truck. The electrical system also can be used as an electrical generator for power tools.

Nevertheless, DaimlerChrysler, maker of Dodge products, seems especially cautious about the future of hybrids, saying it will study the long-term success of hybrids before it moves forward with a high-volume project.

DaimlerChrysler's Thomas Weber says that a drive system so complex as one needed to power a hybrid vehicle can only be successful if it fulfills customer expectations in performance as well as exceeding the fuel efficiency of a diesel engine. “DaimlerChrysler views hybrid technology as an interim step on the path to introducing fuel cell technology,” he says.

DaimlerChrysler will focus its research and product development on clean-burning diesel engines for the near term, and fuel cell vehicles for a hydrogen-powered fuel cell future that could be decades away. The company says it is confident internal combustion engines will remain a vital part of the automotive industry for at least another 20 to 30 years.

Homogeneous-charge compression ignition

The research departments of Ford, GM, DaimlerChrysler, Toyota and other vehicle manufacturers are looking to the diesel engine for ways to improve gasoline engine efficiency. The concept, called homogeneous-charge compression ignition (HCCI), promises a 30% boost in fuel economy, nearly zero emissions and minimal extra expense. The HCCI engine is similar to a diesel engine in that there are no spark plugs. Instead, the piston compresses an air-fuel mixture until increasing heat inside the chamber ignites it. The system gets diesel-like fuel economy without problematic diesel emissions such as nitrogen oxide or soot.

Automotive engineers first conceived of HCCI engines in the 1970s, but those first attempts failed because the engine did not run smoothly. The problem with HCCI is that combustion of highly volatile compressed gasoline is much more difficult to control than combustion of diesel fuel. Engineers now think new electronic control systems can make HCCI engines a reality. GM says it has mastered HCCI combustion from idle to mid-range engine speeds, but it is still having trouble controlling combustion in higher ranges. The aggressive pursuit of HCCI by GM and other companies would suggest that success in making a gasoline engine run as efficiently as a diesel is only a matter of time. Until then, new diesel technologies continue to make the diesel engine itself cleaner and more desirable (see page 14).

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