What feature of the General Motors C.E.C. system is emphasized in the seminar discussion?

The highlighted feature of the General Motors C.E.C. system in the seminar discussion is its ability to provide vacuum spark advance. This function is important because it plays a crucial role in optimizing engine performance and efficiency. Vacuum spark advance allows the ignition timing of the engine to be adjusted based on engine load and speed conditions, enhancing power output and fuel efficiency under varying operating conditions. This system's capability enables vehicle engines to respond better to different driving scenarios, improving overall performance.

The effectiveness of this feature is particularly significant as it helps in reducing emissions and increasing fuel economy, which aligns with industry standards for environmental and economic performance in vehicles. The emphasis on this aspect in the seminar reveals its importance in the context of engine technology and the advancement of automotive engineering.