The performance of four-stroke spark-ignition motorcycle engines is strongly influenced by the precision of fuel injection and ignition timing control. However, factory-set Engine Control Units (ECUs) generally apply fixed calibration maps that are not optimized for varying load and speed conditions, limiting combustion efficiency and output potential. This study investigates the optimization of injection timing and ignition timing using a programmable ECU to improve torque and power characteristics of a four-stroke motorcycle engine. Experimental testing was conducted by comparing baseline performance using the stock ECU configuration against multiple calibration variations executed through a BRT Juken 5 programmable ECU. Engine torque and power output were measured using a chassis dynamometer, while combustion behavior was analyzed through response trends across different engine speeds. The results indicate that advancing injection timing and ignition timing within a controlled range significantly improves combustion stability, leading to increased torque and power output, particularly at mid-to-high RPM ranges. The improvement is attributed to more effective air–fuel mixture preparation and more complete flame propagation during the power stroke. Conversely, excessive timing advance or retardation results in incomplete combustion or detonation tendencies, confirming the need for precise calibration boundaries. These findings demonstrate that programmable ECU-based tuning provides a practical and adaptive approach to enhancing engine performance without requiring mechanical modification, supporting the broader development of electronically optimized combustion systems in small-displacement motorcycles.
Purwanto et al. (Tue,) studied this question.