Injection timing effects on combustion intensity redistribution and pressure-induced mechanical loading were evaluated for a turbocharged diesel engine using a calibrated Diesel-RK simulation model. Engine simulations were performed at multiple load conditions with systematic variation of injection timing. Advancing injection timing shifted combustion toward top dead center, accelerating pressure development and increasing the maximum pressure rise rate from approximately 1.2–1.6 bar/°CA to values exceeding 5 bar/°CA under advanced conditions. The maximum piston gas force increased from 55–70 kN to over 100 kN at high load. The results demonstrated that mechanical loading depended on both pressure magnitude and pressure-development rate, indicating a coupled combustion–pressure interaction rather than a single-parameter response. The results showed that mechanical loading depended on both pressure magnitude and pressure-rise behaviour rather than on a single pressure parameter. Increasing pressure-rise rate intensified piston gas-force response, particularly under advanced injection and high-load operation. The results also indicated that combustion-optimal injection timing did not necessarily correspond to mechanically favourable operating conditions.