Americans may love their huge and inefficient 4WDs, but a longstanding collaboration between the US government and three major car makers has led to the development of some highly efficient auto technology.
The Partnership for a New Generation of Vehicles (PNGV) is a historic public/private partnership between the US Federal Government and DaimlerChrysler, Ford, and General Motors. Announced at the White House on September 29, 1993 by President Clinton, Vice President Gore, and the CEOs of the domestic US car makers, the research program aims to hasten the development of US advanced car technology.
PNGV's long term Supercar goal is to develop an environmentally friendly car with up to triple the fuel efficiency of 1993 midsize cars - without sacrificing affordability, performance, or safety.
The target specifications of this Supercar include:
- Curb Weight - up to 40% weight reduction over 1993 baseline (1450kg)
- Aerodynamic drag - 0.20 Cd
- Friction (rolling resistance) - 0.005
- Engine - flywheels, batteries, or ultra-capacitors
- Fuel Efficiency - up to 80 miles per US gallon (Metro-Highway)
- Emissions - meet Tier II at the default levels of 0.125 HC, 1.7 CO and 0.2 NOx at 160,000km while complying with other Clean Air Act requirements.
- Safety - meet present and future standards.
- Recyclability - at least 80%, up from the 75% 1993 industry average.
In the seven years since the program began, car manufacturers have been active in the development of technologies and concept cars showcasing those technologies. Here's the latest crop.
DaimlerChrysler Dodge ESX3
The Dodge ESX3 builds on the knowledge and experience gained from its predecessors, the Dodge Intrepid ESX in 1996 and the ESX2 in 1998.
An all-aluminium, 1.5-litre direct-injected diesel is the primary propulsion unit, with additional power coming from a lightweight, high power, lithium ion battery. This "mybrid" (mild hybrid) powertrain minimizes demands of electric motor and batteries, therefore lowering the cost and weight of hybridization. A unique electro-mechanical automatic transmission (EMAT) developed by DaimlerChrysler engineers provides the fuel efficiency of a manual transmission with the convenience of an automatic.
The Dodge ESX3 weighs in at only 1022kg, while meeting all Federal safety standards and providing the roominess and comfort of a typical family sedan. A unique thermoplastic injection-moulded body system is estimated to reduce weight by 46% and cost by 15%, compared to steel structures.
The interior systems are optimised for light weight and efficiency, including seats that heat and cool the occupant. The car achieves 72 miles per US gallon gasoline equivalent and has a 250km driving range. With the ESX3, DaimlerChrysler engineers and designers have cut the cost penalty for a high-mileage vehicle in half in just two years. The ESX2 from 1998 cost about US$15,000 more than a comparable gasoline-powered car; with the ESX3, the cost differential is about US$7,500. (The ESX in 1996 carried a cost penalty of US$60,000.)
A total rethinking of the car's electronic and electrical systems cut about a kilogram from the weight of electronics while providing an ergonomically satisfying system of driver controls, vehicle monitoring and diagnostic indicators, high-performance audio and video systems, and a state-of-the-art telematics package.
"With the ESX3, we really are converging on the reality of an 80-mile-per-gallon family car that has the comfort, the utility, the performance and affordability that our consumers demand. PNGV is working - but there is still more work to be done. Consumers want us to produce 'moon-shot' technology at down-to-earth prices," said James P. Holden of the DaimlerChrysler Corporation.
Ford Prodigy
The Ford Prodigy features an aerodynamic design that enhances vehicle aesthetics while reducing air resistance. Prodigy's stunning 0.2 coefficient of drag is a 33 per cent improvement over prior versions of the vehicle. Such a major improvement helps improve the vehicle's fuel economy by 4 miles per US gallon. To enhance the vehicle's aerodynamics, side-mounted cameras and onboard monitors are used in place of conventional side-view mirrors. The cameras provide a needed side view for the driver while not hindering airflow around the vehicle. Variable ride height, grille shutters and shields under the car also add to the vehicle's aerodynamic improvement.
Prodigy's platform is based on Ford's extensive lightweight materials research. Prodigy's total weight is 1085kg, which is about 500kg lighter today's family sedan. The significant weight reduction was achieved without sacrificing package efficiency. Prodigy is 30 percent lighter than today's Taurus sedan, but passenger space and luggage capacity are the same.
Prodigy's low storage requirement hybrid electric propulsion system includes an aluminium DIATA (Direct Injection, Aluminium Through Bolt Assembly) engine, starter/alternator, automatically shifted manual transmission and high-power battery. The DIATA engine is about 35 percent more efficient than conventional gasoline engines. This four-cylinder, 1.2-litre compression-ignition, direct-injection engine generates 55kW at 4,500 rpm. Prodigy's starter/alternator, a small high-power electric motor packaged between the transmission and the engine, delivers additional power when needed. It delivers up to 35kW, for a total of up to 90kW.
The starter/alternator and power electronics module gives Prodigy the capability of shutting off the engine when the car is stopping or coasting to conserve otherwise wasted fuel. Prodigy's DIATA engine restarts in less than 0.2 seconds - literally the blink of an eye - after the driver touches the accelerator pedal. The instrument panel features an energy-flow display that continually shows the flow of the energy in the vehicle. When the engine is off, the display indicates the "ready" status of the engine and the state of charge for the battery electric drive system. Because the engine shuts-off when the vehicle is at rest - such as at a traffic light or when braking - the energy flow display assures the driver that power will be available when needed.
The automatically shifted transmission combines the operating ease of an automatic transmission with the efficiency of a manual transmission. It is 20 per cent more efficient than a typical automatic transmission. Prodigy provides family transportation with 80 miles per US gallon and 400km driving range on diesel fuel; 72 miles per US gallon gasoline equivalent.
"Prodigy goes a long way toward meeting our goal of an extremely fuel-efficient family vehicle. It represents an interim stage between our P2000 research programs and our plans for an affordable, production hybrid," said Neil W. Ressler of the Ford Motor Company
GM Precept
The parallel-hybrid Precept uses the most aerodynamically efficient design in the world, with a drag coefficient (Cd) of 0.163, an astonishing 20 percent less aerodynamic drag than the production record-holder, the GM EV1 (0.19). Such an efficient design accounts for 15 per cent of the vehicle's fuel economy performance. Three-camera rear vision system integrated into a single, central instrument panel display eliminates the need for both inside and outside rearview mirrors. Its four-wheel drive, dual-axle set-up features a 35kW three-phase electric motor driving the front wheels and a lean-burn compression-ignition, direct-injection (CIDI) heat engine driving the rear wheels. This powerplant deliver 80 miles per US gallon gasoline equivalent.
Highly intelligent heating and cooling system anticipates when fog could form on the windshield, and works to prevent it. Four-wheel brake-by-wire system incorporates blended regenerative braking to recover energy from all four wheels. Lightweight construction - including aluminium exterior panels and carbon fibre bumper beams - results in a body that is about 180kg lighter than its typical production counterpart. Energy efficient chassis design, including metal matrix composite mounting brackets and low rolling resistance tires, accounts for more than 15 per cent of the Precept's fuel economy performance.
The brain of the entire hybrid propulsion system is a power PC processor-based controller. This 32-bit, 266 MHz device conducts a two-way dialogue with the following equipment: accelerator pedal, brake pedal, PRND shifter, energy management system, electric traction system, multi-purpose unit, CIDI engine controller, transaxle controller, thermal system controller, and brake controller. As the driver's commands come in, efficiency and emissions optimisation constraints are applied, and digitally coded commands go out. It makes snap decisions to optimise all operations, such as the highly intelligent heating and cooling system. Specifically, the system moves otherwise wasted thermal energy automatically to where it's needed-it even anticipates when fog could form on the windshield and works to prevent it. Throughout the Precept, forty-seven distributed computer modules provide smart control to make this the world's most computerised vehicle.
A key component of the hybrid powertrain is a unique, high-efficiency, automatically shifted manual transaxle. To create the unit, located at the back of the vehicle, GM engineers began with a five-speed manual transaxle from an Opel Astra. By the time the design was finished, not much of the original gearbox was left. Fifth and reverse gears were eliminated (reverse operation is provided by the electric traction system in the front of the vehicle). Gear shifting via clutch was converted to an automatic, computer-controlled operation. As a result, the CIDI engine can be started in any gear, and skip shifting is also possible. In addition, the time required for a gear change, or to start the engine, is about 0.7 seconds. Most importantly, efficiency losses through this transaxle are substantially lower than what automatic or continuously variable transmission (CVT) alternatives would provide.
Another key benefit of the dual-axle, parallel-hybrid approach is that it offers maximum use of regenerative braking through all four wheels. When the driver lifts off the accelerator or taps the brake pedal, unwanted momentum is automatically converted to electrical energy and used to recharge the battery pack located under the front seat. That alone amounts to 13 miles per US gallon in combined city-highway driving, helping the Precept approach its target of 80 miles per US gallon. An ingenious multi-purpose unit handles regenerative braking through the rear wheels in addition to performing five other functions: it contributes 10kW of propulsion power when maximum acceleration is desired, it starts the rear-mounted engine, it powers the air-conditioning compressor when the engine is at rest, the engine can drive it as a generator to recharge the battery and it is used to synchronize the gears for clutchless shifting.
Two of the world's most advanced battery systems are being explored for use in the vehicle - the world's first application of lithium polymer batteries for hybrid vehicle propulsion, and a new generation of advanced nickel metal hydride batteries designed explicitly for the high power encountered in a hybrid propulsion system.
Aluminium is used extensively throughout the Precept's body and chassis components to reduce mass. Like the EV1, the Precept uses a light, stiff space-frame body structure constructed of aluminium stampings, extrusions and castings. Exterior panels are made of aluminium and composite materials. Bumper beams are fabricated with carbon fibre. The mass is 45 percent less than a comparable steel body design.
Since the weight carried by the front tires has been significantly reduced, no power steering assist is necessary. Computer-controlled air springs maintain a level ride height irrespective of passenger and cargo load changes. The springs' source of compressed air can be tapped to inflate the Michelin Proxima radial tires, which have a rolling resistance 10 percent less than the EV1's already low rolling resistance radials. The Precept's Hayes-Lemmerz wrought-aluminium road wheels each weigh only 3.8kg, distinguishing them as the world's lightest 16-inch wheels.
The zero-drag friction brakes for the Precept weigh less than half as much as comparable hardware in today's Chevrolet Impala. An advanced brake-by-wire system uses a small electrically powered hydraulic pump located in close proximity to each brake caliper.
A Motorola-supplied Driver Control Center provides a unique driver-vehicle interface used to operate the car. To start and drive the car, no mechanical key is needed. Instead, the driver enters a five digit security code using the electronic key pad positioned below the display screen, hits the RUN button, and shifts the vehicle out of park and into forward or reverse gear using another set of push buttons.
"Innovation and creativity cannot be forced. They must be allowed to flow freely, giving shape to the wants and needs of the consumer. Above all else, product leadership senses and responds to the demands of the market - and then offers more," waffled Harry J. Pearce, Vice Chairman of GM.
http://www.uscar.org/pngv
http://www.ta.doc.gov
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