Photodiode and Detector

The photodiode and detector control the capacitive discharge ignition system for the engine. The photodiode emits light at a single frequency. When this light is reflected from a coupon attached to the engine flywheel it returns to the photodetector and sends a signal to the capacitive discharge ignition which triggers the spark. The photodiode/ detector assembly can be rotated about the crankshaft, and the crankshaft position at which the reflection occurs therefore changes. This has the effect of advancing (before TDC) or retarding (after TDC) the spark with respect to the engine cycle. This change in spark timing will affect the maximum pressure reached in the combustion process and the work that can be extracted from the working fluid in the engine.