Technology

Move to smaller, lighter cars continues Auto makers are using lighter

metals, more plastics, and

new technology to achieve

federal mileage and exhaust

emissions standards

Ward Worthy C&EN, Chicago

Downsizing is still the dominant theme in Detroit, as auto makers strive to meet ever more stringent federal fuel economy regulations. This year, the corporate av­erage fuel economy standard is 18.0 miles per gallon (mpg). For 1979 models, it's 19.0 mpg. The car companies say they'll beat that figure, but not by much. They'll have to perform even more drastic surgery on their products to achieve the 27.5-mpg average that will be required for 1985 models. However, increased use of plas­tics, aluminum, and other lightweight materials will make it possible to reduce vehicle weight—the main factor affecting fuel consumption—without completely sacrificing the soft ride, spacious interior, and roomy trunk that have characterized "the big American car."

For 1979, the new "full-size" cars from Chrysler, Dodge, Ford, and Mercury are a foot or so shorter and 600 to 800 lb lighter than the corresponding 1978 models. They have roughly the same weights and dimensions as the downsized Chevrolets, Pontiacs, Oldsmobiles, Buicks, and Cadillacs introduced by General Motors in the 1977 model year. Chrysler and Ford, like GM, have gener­ally managed to shrink the exterior

without reducing space in the passenger compartment and trunk. In some in­stances, interior dimensions are more generous than in the earlier, larger mod­els.

Also new from Ford are sporty, sub-compact Ford Mustang and its nearly identical twin, Mercury Capri. Both are now built on a shorter-wheelbase version of the Ford Fairmont chassis introduced in 1978. (Previous Mustang models were derived from the Pinto, and the Capri nameplate was applied to cars imported from West Germany.)

Chrysler has brought out sporty two-door models of its front-wheel-drive subcompacts, Plymouth Horizon and Dodge Omni. Like Mustang and Capri, Horizon and Omni are virtually identi­cal.

GM has downsized its front-wheel-drive specialty cars, Cadillac Eldorado and Oldsmobile Toronado. These cars are almost 2 feet shorter and 900 to 1000 lb lighter than the 1978 models. The new Buick Riviera also shares the same front-wheel-drive chassis; earlier Rivieras used the basic Buick rear-wheel-drive chassis. Otherwise, GM's 1979 models are all "carryover" cars, little changed from 1978. Early next year, however, GM will unveil its new downsized compact line. These cars also will have front-wheel drive.

Ford's Lincoln Continental is now the sole surviving highway behemoth. More than 19 feet long and weighing a little more than 4800 lb, it's about a foot longer and 1000 lb heavier than any other U.S. passenger car now being built, with the exception of Cadillac's stretched limou­sine models. And even those, although almost a foot longer than the Lincoln, weigh less than 5000 lb. The big Lincoln

probably will be replaced by a downsized version in the 1980 model year.

Auto makers could not have achieved the 19.0-mpg average without the downsizing that has already taken place. But if the 1985 requirement of 27.5 mpg is to be met, the average car can weigh no more than about 3000 lb, or about 1000 lb lighter than the current average. If that weight reduction were to be achieved by downsizing alone, the average 1985 car would be no bigger than today's subcom­pacts. To avoid such a fate, automotive engineers are turning more and more to lighter replacements for cold-rolled steel and cast iron.

Plastics are among the leading con­tenders. For example, Ford says that its average 1977 vehicle contained about 165 lb of plastics. Plastics use is expected to reach 280 to 350 lb by 1985, resulting in a reduction of 100 to 150 lb in average ve­hicle weight. Ford notes that substituting 1 lb of plastic for a heavier metal results in about 1 lb reduction in vehicle weight. Thus, although the absolute amount of plastics in a car will roughly double, the percentage of plastics in a car will triple, reflecting the overall reduction in car weight. In addition, Ford points out, there is a "domino effect"—not limited to plastics—whereby the initial pounds saved allow further reductions in the weights of engines, transmissions, and other chassis components.

Although there are dozens of plastic parts in each 1979 car, probably the most notable new technology to appear this year is the use of reaction injection molding (RIM) to make large polyure-thane body parts; specifically, the front and rear fascia of Mustang/Capri models and the front fascia of the Horizon/Omni two-door models.

In the RIM technique, polyol and iso-cyanate are mixed rapidly and injected at high pressure into molds, where the cur­ing takes place. The reaction generates heat enough so that little additional heat is needed. The product, according to Ford, is a flexible plastic material with a high-gloss surface. Thus, it doesn't require the extensive sanding and buffing sometimes demanded by other materials, including metals. RIM parts save weight; for ex­ample, the Mustang/Capri front fascia, with integral grille, weighs only 11 lb. But Ford points out that RIM also makes it possible to execute "distinctive" styling themes that would be impractical with sheet metal. And Chrysler notes that the soft urethane front end can resist impacts of up to 5 mph without damage to ap­pearance or function.

Ford boasts other new plastics appli-1979 Capri has front and rear fascia of injection-molded polyurethane

Oct. 16, 1978 C&EN 25

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Chrysler's large cars have aluminum bumpers and stamped aluminum wheels

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26 C&ENOct. 16, 1978

cations for 1979, including a door window channel bracket of molded polyacetal, a station wagon "load floor" of blow-molded polypropylene, and front fender aprons of injection-molded polypropyl­ene. Chrysler notes that its new full-size cars feature instrument panels made of two injection-molded sections of acrylo-nitrile-butadiene-styrene, ultrasonically welded together.

Aluminum often can provide greater weight savings than plastics. According to Ford, vehicle weight is reduced about 1.3 lb for every pound of aluminum used to replace mild steel or cast iron. Aluminum already is used extensively in engine components and for bumpers and bumper reinforcements. Chrysler says that the chrome-plated aluminum bumpers on its 1979 full-size cars save nearly 60 lb per car but are stronger than comparable steel bumpers. Similarly, stamped aluminum wheels on Chrysler full-size models result in a weight loss of 35 lb per car.

Despite the inroads being made by plastics and aluminum, much of the steel in today's cars will be replaced in tomor­row's lighter models by so-called "high-strength" steels. These steels, which are made by adding small quantities of nio­bium and other metals, have yield strengths one and a half to three times the yield strength of conventional low-carbon steels. The obvious advantage is that it takes less steel to perform a given func­tion. However, one disadvantage of high-strength steel is that it's tougher and more difficult to shape into complex parts. High-strength steels currently find application in such parts as side-impact beams, bumper support bars, and body panels—for example, the hoods of Hori­zon/Omni four-door models. This year Ford also is using high-strength steel in frame sections for its full-size cars.

Even glass provides opportunities to shed a few pounds. Ford notes that use of thinner glass in all its 1979 vehicles will result in an overall average weight saving of about 20 lb per car. As one example, the new Mustang's rear window is made of 0.156-inch-thick glass, instead of the 0.23-inch glass used previously for similar applications, for a weight reduction of 7 lb. Ford points out, however, that the thinner glasses must pass the same

strength tests as the thicker panes for­merly used.

Some of the weight-cutting tricks are less admirable. For example, "mini" spare tires have become almost universal. And the batteries in some of the new cars would look more appropriate on motor­cycles. Still, the pounds have to go, and those are among the ways of getting them off.

Drive trains also are changing. Big en­gines of 400-cu-in displacement (CID) and above are fast disappearing from the passenger car scene; the only ones left in 1979 are Cadillac's 425 CID and Lincoln's 400 CID. Otherwise, the largest available engines are GM's 350 CID, Ford's 351 CID, and Chrysler's 360 CID. And these are being "de-emphasized" in favor of smaller eight-, six-, and four-cylinder engines.

GM is extending the availability of the Oldsmobile-developed 350-CID diesel V8, introduced as an option in 1978 full-size Oldsmobiles and Cadillac Sevilles. This year the engine is also offered on inter­mediate Oldsmobiles, as well as on the Oldsmobile Toronado and the Cadillac Eldorado. Oldsmobile notes that a new fast-start system makes it possible to start the engine in about six seconds at 0° F. Last year's diesels needed 60 seconds to start at that temperature.

Oldsmobile also is bringing out a new 260-CID diesel V8, initially available on its intermediate coupes and sedans. This engine will be converted to the fast-start system sometime during the current model year. GM notes that the 350-CID and 260-CID diesels both meet current emission standards without the use of catalytic converters or exhaust gas recir­culation.

Of course, fuel economy is the diesel's forte. For example, according to EPA figures, the 1979 Toronado with 350-CID gasoline engine gets 16 mpg "city," 22 mpg "highway," GM says. With the diesel of the same displacement, the Toronado figures are 21 mpg "city," 29 mpg "high­way." However, "performance" does suffer; the gasoline engine develops 170 hp at 4200 rpm, whereas the diesel turns out only 120 hp at 3600 rpm.

Ford offers an optional turbocharged 2.3-liter, four-cylinder engine on its new

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Oct. 16, 1978 C&EN 27

Mustang/Capri models, and Buick has increased the availability of its turbo-charged V6 engine, introduced on 1978 models. According to the makers, the turbocharger (a compressor driven by exhaust gases) increases engine efficiency by "force-feeding" fuel/air mixture into the cylinders.

Exhaust emission standards for pas­senger cars are the same as for 1978 models. However, more three-way cata­lysts are showing up this year, particularly in cars destined for California, where emission standards are stricter than for the rest of the U.S. The three-way cata­lysts oxidize hydrocarbons and carbon monoxide and simultaneously reduce oxides of nitrogen. Doing this effectively requires a near-stoichiometric fuel/air ratio, and achieving that condition in an engine operating under varied conditions calls for some pretty complicated hard­ware.

One example is Ford's new EEC-II electronic engine control system. A sensor in the exhaust manifold measures the oxygen content of the exhaust gas. Other sensors constantly monitor crankshaft position, throttle position, coolant tem­perature, manifold absolute pressure, barometric pressure, and exhaust gas re­circulation valve position. A digital mi­croprocessor uses that information to calculate spark advance, exhaust gas re­

circulation flow rate, and fuel flow trim requirements; at the same time, it sends electrical signals to control the solid-state ignition module, the exhaust gas recircu­lation valve actuator, and an electric stepper motor (in the carburetor) that controls the fuel flow rate and thus the fuel/air ratio. According to Ford, the new system provides improved fuel economy as well as lower emissions. It also elimi­nates the need for special calibrations in high altitudes, since the system auto­matically compensates for changing at­mospheric pressure.

Hardly any approach is overlooked in the campaign to improve fuel economy. Axle ratios are lower. Overdrive trans­missions are reappearing in a number of models. Chrysler is extending the use of its lockup torque converter, which, at highway speeds, eliminates the energy loss caused by slippage of the fluid cou­pling of an automatic transmission. Since air drag can waste a lot of fuel, all the car makers are giving more attention to the aerodynamics of their car bodies. Also, tire pressures are going up, to reduce losses from rolling friction. Cadillac, for example, notes that recommended tire pressures for its cars have been increased from 26 psi to 32 psi. However, Cadillac assures potential buyers "a sophisticated retuning of the structure" has preserved the traditional Cadillac ride. Π

On-line coal and oil analysis developed A noninvasive, nondestructive system to analyze coal streams for 12 elements on-line by neutron-induced gamma ray spectrometry will be delivered to the Homer City, Pa., plant of Pennsylvania Gas & Electric Co. at the beginning of 1979. And, Herbert Deich of MDH In­dustries, Monrovia, Calif., told a recent conference on utilization of californium-252 in Atlanta, a similar system for oil streams will be installed at a refinery next spring.

Rapid, on-line sulfur analyses with the new 252Cf devices will enable plant oper­ators to respond at once with measures to meet air emission standards. Determi­nations of ash-forming elements will allow engineers at coal-burning facilities to adjust burning conditions quickly. Oil refinery technicians will benefit from detection of elements that poison cata­lysts.

A close second in developing such de­vices is Science Applications, La Jolla, Calif., which expects to deliver its first instrument to a coal-burning utility late in 1979. Also at the conference, Dr. Caroline Herzenberg of Argonne National Laboratory described her work to adapt 252Cf technology to coal conversion plants.

The MDH system will be able to detect carbon, hydrogen, nitrogen, sulfur, silicon, aluminum, iron, titanium, calcium, po­tassium, sodium, and chlorine, Deich says. The instrument contains a 200-micro-gram 252Cf source, which emits 2.3 million neutrons per second per microgram.

28 C&ENOct. 16, 1978

M

Neutrons cause bombarded atoms to emit gamma rays at energies characteristic of each element. A microcomputer analyzes radiation intensities averaged over many determinations and prints out results in minutes.

Oxygen, phosphorus, and magnesium are other elements important to fuel analyses, but neutron cross sections of these elements are too low for accurate determinations. Sodium and potassium are also difficult and require averaging over about an hour for accurate determi­nations, Deich says.

Herzenberg also has studied carbon/ oxygen ratios in simulated coals to de­velop methods to determine oxygen. She says semiempirical formulas exist to convert elemental content of coal to heat content. These formulas may facilitate use of such instruments as "Btu me­ters."

Neutrons also induce radioactivity in elements, and Herzenberg has used this radioactivity to measure flow rates. This technique will be useful in coal conversion plants where two-phase coal streams in gas or liquid must be followed in hot, abrasive, corrosive, high-pressure envi­ronments, she says.

Fuel analyzers thus may become an important use of 252Cf outside the nuclear industry, where most of it is used to manufacture isotopes or to start up nu­clear reactors. In addition to operating a 252Cf loan program, the Department of Energy's Savannah River plant shipped 30 mg of it to buyers in 1977. Π

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