''We're not ready to say that ceramics have arrived,'' says Albert H. Bell III, the executive engineer in charge of General Motors's advanced product and manufacturing engineering staff. ''But ceramic development is moving ahead fast.''
In a series of tests by Hitachi Ltd. of Japan, ceramic pistons and cylinders used on a 2-liter engine received a high grade from experts.
Made from a new silicon carbide ceramic developed by the Japanese company several years ago, the diesel-engine components were built ''as a means of proving the excellent properties of the new material,'' says a spokesman.
Hitachi has been working on possible practical applications for the highly tensile ceramic, which, the company says, has good insulating capability yet is also heat conductive. They plan to test the material in larger structures, such as gasoline turbines and large-capacity engines.
There are two basic types of ceramics. One is a strong, high-temperature material, while the other is a poor conductor of heat that is used for insulation. ''They are both very brittle,'' explains GM's Mr. Bell, who has been involved in turbine research for 37 years.
''Ceramics are extremely good in areas where heat resistance is important, because when you get up to, say, 2,500 degrees (turbine engines), you have to use high-cost exotic metals to withstand that kind of temperature,'' reports John D. Withrow Jr., executive vice-president of product development at Chrysler Cor-poration. ''When you start comparing ceramics against metals of that exotic nature, ceramics begin to look pretty good economically.''
In contrast to exotic metals, ceramics are very cheap.
''You'd do an all-new car for this kind of application because you wouldn't get the maximum advantage out of it otherwise,'' Mr. Bell explains. ''You'd want an engine that is very lightweight and free of vibration,'' he adds. ''What this means is a turbine, but it may not happen before the mid-1990s.''
''We no longer fly piston engines,'' he continues. ''A turbine has very high durability and an efficiency advantage as much as 15 to 1 over the piston engine , because it has a better temperature ratio.''
GM is currently developing a brand-new, compact turbine engine that is far smaller, and much lighter in weight, than anything else around. In output it would be equivalent to a small 4-cylinder piston engine. GM wants the ''baby turbine'' to be ready to go when the ''ceramic era'' arrives.
Besides GM, West Germany's Daimler-Benz also has a state-of-the-art turbine that its research engineers have run. Ceramic blades are inserted in a metal turbine wheel. Volkswagen and Volvo also are working in this field, as well as others.
Nissan, the Japanese carmaker, has a ceramic gas turbine that it plans to put into production sometime down the road. It's not an ''idea car,'' Nissan insists , but a pre-prototype concept car.
A year ago at the Tokyo Auto Show Isuzu Motors showed an experimental diesel engine with ceramic parts.
''In the automobile (piston) engine of today we don't work at those high-temperature levels (2,500 degrees F.) - not that we wouldn't like to, but the higher the temperature in the combustion chamber, the more difficult it is to control the oxides of nitrogen (NOx) levels,'' says Mr. Withrow.
''NOx doesn't form below 2,000 degrees F. One of the things we try to do is even out the temperature in the combustion chamber so that we don't get peak temperatures that create NOx.''
Ceramics may also play a part in areas of a car that are difficult to control by lubrication.
''I think we'll begin to see some of these kinds of things happen with ceramics, such as rocker arms and shafts, coatings on pistons and camshafts, and the like,'' Mr. Withrow predicts.
The trend once again is economic. Engineers are asking: ''When do ceramics begin to pay for themselves?''
''Mass-production technology of ceramics is still inadequate,'' says Yutaka Kume of Nissan, ''so it is unlikely that they will come into wide use as structural materials for some time to come.''
Even though the wide-scale application of ceramics in auto engines is far down the road, the ultimate advantages to the motorist are great.