DETROIT - Aluminum, titanium and stamping have been yielding slowly to pressure from nylon and lost-core molding technology for making automotive air-intake manifolds. And, another dramatic change may come with conventional injection molding succeeding the more expensive melt-core injection molding process now used.
Three U.S.-built cars with the plastic air-handling systems - Cadillac's Seville and DeVille, and Oldsmobile Aurora - have strong appeal to carmakers because of qualities that include cost, noise management, reduced weight, and smooth surfaces, engineers say.
At least 37 manifold projects are in the works around the world, and more are expected.
European companies have taken more readily to the plastic systems. The manifolds were used as early as 1972, when they were installed on the German-built Porsche 911 V-6 power plant. BMW and Ford Motor Co. followed in later years with applications on high-volume cars.
Leaders in the field are BASF Corp. Plastic Materials Group of Mount Olive, N.J., and Freuden-berg-NOK's Plastic Product Division in Manchester, N.H. Executives with those companies discussed the manifold work at the recent SAE International Con-gress and Exposition in Detroit.
They predict that in five years, some 40 million pounds of reinforced nylon will be used annually around the world to make manifolds. There are about eight pounds of resin and glass per manifold.
Freudenberg-NOK is a 14-plant, 3,600-employee partnership of Freudenberg & Co. of Germany and NOK Corp. of Japan.
The company produces the 35 percent glass-reinforced nylon 6/6 intake manifold for the 1995 Cadillac Northstar V-8 engine on a 750-ton injection press in Manchester. That car had used a titanium manifold.
BASF is working on 26 manifold-development projects in Europe, nine in the United States and two in the Far East, said Reinhard Katz, group vice president for the materials producer.
``For the Northstar project we used the lost-core process. But, in the future not all manifolds will use this process,'' Katz said.
``Some will use the so-called clam shell, or welded, approach, which is less expensive,'' he said.
Others called the welding method less costly in terms of reduced equipment and tooling investment.
``Welding technology is improving steadily,'' Katz said. ``And, more complicated designs are being considered, including manifolds with more than two parts.''
Engine builders have said they expect to ask more of manifolds in coming years with the addition of molded-in parts like throttle bodies, fuel rails and fuel injectors.
Katz said glass-reinforced type 6 nylon may replace nylon 6/6 for manifolds because it is recyclable and easier to weld than nylon 6/6.
While saying welded parts loom large in the future, Katz said work is progressing on getting cost out of lost-core processing and speeding it up.
