Real-time Piston Temperature Measurement using Induction Telemetry System

The durability of a piston is an essential factor that limits the engine performance. The temperature of a piston, therefore, is valuable information for the development of an engine. As the conventionally applied material hardness method is not a direct measurement of temperature during operation, this method is useful only under constant-speed operating conditions and unable to satisfy various demands of piston temperature measurement. The authors have, therefore, developed the piston temperature measurement system that withstands high engine speed using the compact and light-weight electromagnetic induction method that permits direct measurements of piston temperatures with a thermistor and allows measurement information exchange near the bottom dead center. The system is applicable to motorcycle engines which often use high speed allows measurement up to 15,300 r/min and assures durability and reliability for more than 10 hours.

In this report we introduce actual examples of piston temperature changes measured by the electromagnetic induction system with the typical parameters altered when the engine is operating. The phenomenon that the piston temperatures become less sensitive to changes of parameters under high engine speed conditions is thus explained by the difference in the heat transfer rate of heat input side and the heat release side.