New Regulations Spur New Technology New Regulations Spur New Technology

This article is excerpted from Technology Trends in the new AUTOFACTS Global Powertrain Strategies syndicated report. The 3,000-page, multi-volume study is the industry's first comprehensive analysis of the worldwide market for light vehicle engines, transmissions, and related components. Primary contributors to this article were Dean Bedford, Pete Langlois, and Karey McCann.

Powertrain technology is not only a determining factor in the light vehicle marketplace; the rate of development of that technology will influence the extent and timing of shifts in penetration of components - diesel engines, CVTs and semi-automatic transmissions.

Performance, Utility and Cost
Between now and 2005, the major driver of powertrain technology will be the increasingly stringent emissions and fuel economy regulations imposed on passenger cars and light-duty trucks in most major global market areas. The Climate Control Conference held in Kyoto, Japan, in late 1997 underlined the preeminence of environmental issues as drivers of powertrain technology. Paired with that is market pressure on VMs to make their products comply with environmental regulations without reductions in performance and utility. The driver of next importance is the necessity of keeping all powertrain costs under strict control to minimize the overall impact on vehicle market prices. This will push the development of less costly production technology for powertrain components, as well as the refinement of product designs to achieve cost reductions.

Emissions: Targets keep moving
Although notable strides have been made in the reduction of automotive emissions, pending regulations - especially in North America and Western Europe - require still further reductions. As a result of the Kyoto Conference and the subsequent climate control meeting in Buenos Aires, these regulations are receiving renewed scrutiny, which could both accelerate the timetable and toughen the restrictions. Technology to achieve the reductions must focus on the combustion process itself, as well as the design of major engine components and particulate traps. Emphasis will be placed on the start-up and warm-up phases of the operating regime, when most of the pollutants are emitted. Necessary technologies range from heated catalysts to changes in component material specifications to assist in reducing vehicle weight.

Low Mass and Reduced Friction
Mandated reductions in vehicle fuel consumption, either for resource conservation or abatement of greenhouse gases, particularly CO
2 , will also influence powertrain technology. Though reduction of powertrain mass is essential to improve fuel economy, technology also will be directed toward improving cycle efficiency through the further development of the direct injection (DI) combustion process for spark-ignition and diesel engines. Higher specific output will not only reduce the engine size and mass required to achieve a desired performance level, but also improve vehicle fuel efficiency through reduced friction horsepower.

TECHNOLOGY CHALLENGE:

Cheap may be expensive
Cost reduction will spur new developments in production technology for all components, and cause designers to re-think material specifications. Increasingly, cost reduction will focus on the entire vehicle, rather than proceed component by component. It might be more cost efficient to choose a more expensive but lower mass material for a particular component than to reduce weight in other parts of the vehicle: the best example is the increased use of aluminum to substitute for less expensive cast iron for engine blocks and heads.

Engine Technology
The internal combustion engine will remain dominant in light vehicles despite significant progress in automotive fuel cell technology. Hybrid internal combustion/electric vehicles will expand EV applications, but widespread use awaits commercial development of the fuel cell. Inline four-cylinder configuration will dominate engines of less than 2.5 liters displacement, with three-cylinder design increasing for engines under 1.0L and five cylinders for engines over 2.0L. For larger engines, the share of "V" configuration engines will continue to grow, frequently due to vehicle packaging considerations. Globally, the typical spark-ignition engine will displace 2.0L or less with four inline cylinders, using overhead camshafts and a multivalve configuration with aluminum head. For passenger cars, four-cylinder block composition will increasingly move toward aluminum for vehicle mass reduction. Fuel systems will be multi-point fuel injection, with electronic controls linked to the emissions system and transmission. Six-cylinder designs will continue to dominate between 2.5L and 3.8L, with some inroads by inline five-cylinder design for engines of 2.7L or less.

The continued development of NVH reduction technologies and more sophisticated powerplant mounting systems have freed engine designers from the restriction of an even number of cylinders and a limited number of "V" engine bank angles. The number of three- and five-cylinder designs will increase over the time period as more producers install "modular" engine production facilities.

Because of the sensitivity of the diesel combustion process to changes in combustion space dimensions, diesel designers have long treated the individual cylinder as a "module", to be combined in the required number to produce the engine output desired. Even though spark ignition engine designers have until now enjoyed more freedom in combustion space dimensions, their need for lower emissions and more efficient production have caused them to adopt the "modular" approach as well. This will increase the number of three-cylinder in-line engines with displacements of 1.0L and less and the number of five-cylinder engines with displacements between 2.0L and 2.7L.

Although the V6 configuration will dominate engines between 2.5L and 3.8L, the excellent NVH characteristics of the in-line six (if the crankshaft is designed with sufficient torsional stiffness) renders it ideal for those designs that can accommodate the additional length vs. a V6 of similar displacement. Therefore, some VMs are evaluating small I6 engines of approximately 2.5L displacement for use in transverse mounted, front wheel drive (TFWD) passenger cars. The impetus here is not only NVH (to which the TFWD layout is sensitive) but also the additional "crush" space within a given vehicle's sheet metal - especially important when a six-cylinder engine is a lower-volume option to an I4 engine.

Degrees of difference
V6 bank angle will not be restricted to the traditional 60 and 90 degrees. 60 degrees offers superior NVH (90-degrees needs a balance shaft) and better fore and aft crush packaging in TFWD. All this is obtained at the expense of the design environment for the intake manifold, due to the narrower space between the banks. Therefore, 60-degrees or less will be used in TFWD installations. 90-degrees will be used for longitudinal designs by VMs who develop "modular" six- and eight-cylinder production facilities, like those for the latest Mercedes M112/113 engine series.

Increase Everything But Cost Increase Everything But Cost

For car applications over 3.8L and light truck uses over 4.3L (mostly North America), the 90-degree V8 will remain the design of choice. There will also be the limited use of modular V10s in light trucks, and a small number of V12s consumed in specialty vehicles.

For eight-plus cylinder engines, packaging considerations, as well as crankshaft torsional rigidity, will continue to make the "V" configuration mandatory. While in-line six-cylinder designs offer advantages in balance and vibration, similar packaging considerations will favor the "V" for both spark-ignition and diesel engines. The 90-degree bank angle, which minimizes disturbing forces, will be used for most V8 engine designs. However, the V6 configuration will, in addition to the more common bank angles of 60 and 90 degrees, have its cylinders united in angles ranging from 15 to 75 degrees. A few VMs will continue to use the horizontally opposed (180 degree bank angle) design for engines of four and six cylinders. Almost all spark-ignition engines will continue to be fueled by gasoline. Some alternative energy sources, principally natural gas, will develop a minor market as a fleet fuel, spurred by political or economic incentives.

DI becoming more popular
The typical diesel engine for light vehicles will be an overhead camshaft I4. Improvements in combustion chamber design, injection systems and electronic controls will permit the more efficient direct injection combustion system to replace indirect injection systems. The capabilities of the modern DI diesel are leading some producers, especially Europeans, to develop full DI diesel lines, with most using common rail technology.

For the foreseeable future, the low energy density of available storage batteries will severely restrict the operating range of electric vehicles, rendering them useful only in niche markets. The fuel cell holds the promise of liberating the electric highway vehicle from an extension cord. The design currently under investigation is the proton-exchange-membrane (PEM) fuel cell. Current development has evolved much more rapidly than initially anticipated, but even if these vehicles are production ready, major improvements in infrastructure supplying the needed hydrogen or methanol fuels will be necessary before they occupy a significant share of the market.

Several manufacturers have produced vehicles with hybrid power-plants combining internal combustion and battery power. The hybrid powerplants that are currently showing the most promise and are undergoing the most development are of a "Parallel" design, in which the internal combustion and electric vehicle drive systems are completely independent. "Series" hybrid powerplants, in which the vehicle wheels are driven by an electric traction motor that can have multiple energy sources, incur higher costs at this time with the use of a larger electric motor and/or generator. Hybrid vehicles being tested now show promise to be production ready with little or no economic or convenience drawbacks in the next few years.

Transmission Technology
Little change is anticipated in manual transmission technology through 2005, primarily because their penetration in more technically sophisticated markets is expected to remain steady or decline slightly. Manual transmissions will continue to account for over 85% of transmission applications in West Europe and remain the transmission of choice in developing markets as well.

The major advances in automatic transmission technology through 2005 will be in controls rather than basic design. With very few exceptions (Honda, Mercedes-Benz, and Saturn) automatic transmissions will continue to use epicyclical gearsets. Those few exceptions are of two-shaft design, like a manual, with hydraulic clutches in place of the synchronizers and mechanical clutches of the manual.

Several VMs plan to use semi-automatic transmissions in applications all the way from small city cars (the MCC Smart) to exotic sports cars from Ferrari. Most semi-automatics use manual gearset technology with a friction clutch rather than a torque converter. Many will appear on economy cars to avoid the additional cost and mass of a conventional automatic or its negative impact on fuel economy.

Powertrain Technology Powertrain Technology

Two developments have unleashed the potential of the continuously variable transmission (CVT): electronic controls and push belts with high torque capacity. Belt development will soon raise the displacement limit above the current 2.5 liters, possibly to four liters. With electronic controls giving CVTs performance and economy close to a five-speed manual, the CVT could challenge the latter in market segments where fuel economy concerns have kept out automatic transmissions - although CVT penetration globally is expected to amount to only one-half million units annually by 2005.

Electronic Controls : more with less
Powertrain electronics are key to achieving compliance with the ever more stringent emissions and fuel consumption regulations of the next seven years. At the same time, more compact vehicles need these components to occupy less space. Powertrain controls are no longer stand-alone components, but must interact with chassis and body control systems - with ever-higher reliability and durability. As electronics control more critical functions, VMs are painfully aware of litigation exposure to malfunction of both hardware and software. Therefore, VMs will use separate control modules for critical functions such as throttle control, and use specific modules for engine and transmission instead of combining them.

 

The increasing number of functions under electronic control places more demands on control system input devices. Output devices also are expanding in type and complexity. Vacuum operation may be used for simple on/off operations with low power requirements such as manifold butterfly valves, but electric or hydraulic actuation will see increasing use. More multiplexing will be used, to reduce the complexity and cost of wiring harness needed for control functions.

Combustion
All but a very few spark-ignition engines operate on air/fuel ratios close to stoichiometric, with throttling of the intake air charge used to control engine output. Some utilize lean-burn technology with either conventional or DI fuel systems, the latter gaining in application because it improves fuel-economy - with increased fuel and emissions-system costs. Spark-ignition engines using this technology can rival an IDI diesel engine in fuel efficiency, but come up 15% short of a modern DI diesel. Unfortunately, since current technology makes their NOx emission control extremely difficult, increases in lean-burn, DI spark-ignition engines depend on development of "lean" NOx catalysts. Since most fuel economy gains achieved by DI "lean burn" technology result from the reduction of pumping losses due to the ability to operate unthrottled, DI is most effective when applied to larger displacement engines. Paradoxically, the lack of effective NOx controls has restricted the initial production use of this technology to small displacement engines in lighter vehicles.

 

AUTOFACTS' Global Powertrain Strategies includes: Regulatory Trends; Technology Trends; Engine & Transmission Consumption Outlook; Vehicle Manufacturer Powertrain Strategies; Powertrain Supplier Competitive Analysis. The complete study is available now in print and electronic formats. For more information, call Chris Benko or Pete Langlois at 800-729-4748.