Analysis of application of chosen methods for tdc determination in marine diesel engines

In the operating marine diesel engines the indication diagnostics tests are usually performed through a 0.5-1.0 me ter long indication channel which delays and disfigures the pressure signal being measured. the delay depends on the engine 's speed and load. the pressure sensor itself together with an amplifler is an additional source of delay and disfigurements, so the registered pressure curve is displaced even if theTDC piston's position hadbeen estimated with the highest accuracy. when the over exploited engine is being tested the angle of delay can achieve several degrees and differ for each cylinder. in that case cylinders' load is unequal and torsional vibrations occur in the engine operation. in case when some simplifying assumptions have been adopted the part of diagnostic information is lost what could lead to a false diagnosis. in the paper the attention is focused on the mistakes which could be made in the marine diesel engine diagnostics when different TDC assessment methods are used. TDC corrections with compression pressure analysis are possible only in case when crankshaft angle position is precise. in case of measurement with constant frequency such corrections are possible only when the engine is good balanced.