# Effect of Performance by Excessive Advanced Fuel Injection Timing on Marine Diesel Engine
## 2 Methods  
### Experimental Methods  
The target engine used in this study was an inline 8-cylinder medium-speed diesel engine commonly employed for propulsion, exhibiting abnormal noise and vibration phenomena during operation. The target engine had the following issues during starting and operation.  
* The flywheel's TDC mark and the piston's TDC did not align, and the fuel injection timing was adjusted based on the flywheel TDC mark of each cylinder.
* While diesel engines with 6 or more cylinders could start at any crank angle, the target engine had a specific crank angle, where air running was not possible. Therefore, it was set to turn after the TDC mark by 10 \({}^{\circ}\)CA before attempting to start the engine.
* Two to 3 failed start attempts occurred before the transition to fuel running. This phenomenon was more pronounced when the engine's preheating was insufficient.
* Compared to other engines, the target engine exhibited more vibration and noise, especially a dull noise, such as knocking during no-load (idling) operation.  
Table 1 presents the detailed specifications of the target engine. According to the normal continuous rating (NCR), the engine operated at a speed of 620 rpm, and the maximum continuous rating (MCR) output was 3310 kW. The fuel injection pump was a spill port type with a mechanically controlled fuel injection method, in which the injection timing was determined by the camshaft.  
Figure 1 illustrates the configuration of the experimental setup used for diagnosing the target engine. The crank angle sensor, an encoder, was installed at the front end of the engine to acquire pulse signals in the data acquisition system. Combustion pressure data from each cylinder were collected using combustion pressure sensors. A damper was installed at the front end of the engine, where the encoder was positioned to counterbalance torsional vibrations and axial vibrations.  
\begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Model Engine Specification**} \\ \hline Type & YANMAR 8N330-EN (4-stroke diesel) \\ Bore/stroke & 330/440 [mm] \\ Cylinders & 8 \\ Fuel injection pump & Spill port type mechanically controlled by camshaft \\ compression ratio & 13.5:1 \\ Firing order & 1-4-7-6-8-5-2-3 \\ Normal rated speed & 620 [ rpm] \\ Maximum output & 3310 [kW] \\ Maximum pressure & 12.2 [MPa] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Engine specification.  
Figure 1: Schematic diagram of the experimental device.  
Figure 2 shows the waveform of the angle encoder. The encoder used in the experiment was an incremental encoder with a reference pulse (Z pulse). The A and B pulses had a phase difference but the same resolution, while the Z pulse had a pulse width of 1/4 of the A and B pulse widths. With the engine in a stopped state, the reference pulse of the encoder, Z pulse (which occurs once per revolution), was aligned with the No. 1 cylinder TDC mark on the flywheel. By utilizing the A and B pulses, the TDC of the eight cylinders, following the firing order, could be obtained at intervals of 720 \({}^{\circ}\)CA (2 revolutions, 1 cycle) relative to the TDC of the No. 1 cylinder. The data sampling was triggered by the \"A\" pulse of the angle encoder, and the sampling was performed using a 720-pulse encoder per revolution, acquiring data at intervals of 0.5 \({}^{\circ}\)CA.