Cars today have more electronic content than ever, which means more circuits, more wiring, and more weight. At the same time, automotive semiconductor and networking technologies pack more performance into smaller space. How does that net out?
I posed the question to Paul Geyer, who has design responsibility for connectors, schematics and wiring tools in Chrysler’s Power and Signal Distribution group and is also one of Chrysler’s managers at the United States Council for Automotive Research (USCAR).
“The general trend in wiring is always to increase the number of circuits in the vehicle. Communication between modules has slowed the growth of circuits but the proliferation of new options on vehicles and higher emissions standards have balanced that out to the point that we still increase the number of circuits on every generation of vehicles by 3 to 5 percent, depending on vehicle class, with higher end cars adding more circuits,” Geyer says.
Networks mitigate that growth, but not by all that much. Geyer estimates that without networks, circuits would increase by 4 to 6 percent. “When a new feature comes in, the first generation requires a separate box. When the next generation comes into play, those functions typically get integrated into one box with a lot of communication between those features internal to that box. Over time, I see the number of circuits leveling out and electronic integration helping to keep those circuits at a manageable level,” Geyer says.
Geyer has seen enormous improvements in automotive wiring technology in the course of his career. “We’ve gone from very crude, large, bulky connector systems that we used to have in the early 1980s to very high tech connector systems that have very small pin-to-pin spacing, redundant features in the contacts, precious metal plating where required, backup systems for sealing, secondary locks to prevent push-out, and mate assists to keep the ergonomic effort low enough for the operators to handle,” he says. “It’s like comparing an old time car to a new car in terms of features – the same kind of change.”
And collaborative efforts at USCAR have helped.
“One of the best results out of the USCAR collaboration was a common test bed, SAE/USCAR-2. That allowed Ford, GM and Chrysler to come together with one set of common test parameters. Prior to that, the OEMs all had their own performance standards for electrical wiring and connections. Almost everything back then was a high current electromechanical device. Connector suppliers had their own specs. There was really no single, unified spec that every connector supplier could test to satisfy the requirements for the Big Three. This had a significant impact on cost, time to market, and reliability.”
Another spec, SAE/USCAR 21, provides a performance standard for crimping of terminals on the wire. “In the past, crimps were mechanically tested. Now, with USCAR 21, there is a very rigid set of environmental, conductivity and vibration profiles that crimps are subjected to, and that has gone a long way to help reliability of these electronic systems. The result is a cleaner and more electrically secure connection.”
Geyer says improvements in wiring and connector technology have had a significant impact on vehicle reliability. “With commonization and USCAR testing I don’t have to do a lot of testing on individual components. I know the part is going to perform and I will have a reliable system.”