# Effect of Performance by Excessive Advanced Fuel Injection Timing on Marine Diesel Engine
## 1 Introduction  
The output of a ship diesel engine for propulsion can be measured using the pressure measured inside the cylinder, and if the pressure inside the cylinder cannot be measured, the shaft horsepower (SHP) or brake horsepower (BHP) can be calculated through the torsion meter of the propulsion shaft. Indicated horsepower (IHP) calculation by measuring the combustion pressure of fuel inside the cylinder requires a crank angle sensor and a cylinder pressure sensor. Research and devices have been developed and applied to measure accurate output performance and reduce combustion analysis errors by supplementing top dead center (TDC) errors [1; 2; 3; 4; 5; 6; 7]. The reason for the discrepancy between the calculated engine output through combustion analysis and the measured engine output is due to TDC error. The causes of TDC error can include errors in the encoder pulse waveform, errors in the flywheel TDC mark, loss-angle error due to heat loss caused by the compression process of the actual engine not being adiabatic, loss-angle error due to pressure loss caused by blow-by gas, torsion of the camshaft, and errors in the connection between the encoder and the camshaft [1; 2; 5; 8]. When measuring engine output, a TDC error of approximately 10% in diesel engines and approximately 4% in gasoline engines can cause errors in the indicated mean effectivepressure of about 1.0 \({}^{\circ}\)CA and in the rate of heat release (ROHR) of about 25% [1]. Therefore, it is necessary to ensure at least a 0.1 \({}^{\circ}\)CA accuracy range for the TDC position. Fuel injection timing greatly affects the performance and emission characteristics of diesel engines. The timing of fuel injection varies with engine speed, and in the case of low-speed engines, the injection timing is slower than it is in high-speed engines. Various studies have reported the effects of different fuel injection timings on engine performance and combustion characteristics. [PERSON] et al. investigated the influence of fuel injection timing on the ignition and combustion characteristics of dual-fuel engines with a large bore [9]. [PERSON] et al. reported on the combustion and emission characteristics by varying the fuel-spray angle and fuel injection timing conditions in a high-speed diesel engine [10]. [PERSON] et al. presented research results on the reduction of NOx emissions by retarding fuel injection timing in an engine using biofuel. However, this was accompanied by a slight decrease in brake thermal efficiency [11]. On the other hand, [PERSON] and [PERSON] achieved simultaneous improvements in brake thermal efficiency and a reduction in NOx emissions by using higher fuel injection pressures and faster fuel injection timing in an engine using biofuel [12]. For optimal combustion in diesel engines, fuel injection occurs before TDC, resulting in a period of ignition delay until compression ignition occurs. The extent of ignition delay significantly affects the subsequent combustion state. On the other hand, excessively advanced fuel injection leads to a sharp increase in combustion pressure, causing diesel knocking and thermal stress, reducing the reliability and durability of the engine [13; 14; 15]. To improve combustion conditions at low loads, a variable injection timing (VIT) system is applied and used in ships, which advances the fuel injection timing compared to the normal setting [16]. Furthermore, excessively advanced fuel injection timing can generate a torque in the opposite direction of the crankshaft due to the peak pressure occurring at before top dead center (BTDC) during the piston's upward motion. In multi-cylinder engines, if the injection timing varies between cylinders, it can unevenly affect the rotational force on the crankshaft [17]. To obtain the most efficient rotational power of the crankshaft, it is necessary for the fuel to be injected before TDC, allowing for a period of ignition delay. Afterward, the combustion should initiate at TDC, ensuring that the explosive pressure is fully utilized in the expansion stroke.