Main Engine 4-Stroke · Main Engines (4-Stroke)
The 6L21/31 engine operates on a four-stroke cycle with a bore of 210 mm and a stroke of 310 mm. Manufactured by MAN Energy Solutions, this engine is designed for heavy fuel oil (HFO), marine gas oil (MGO), and marine diesel oil (MDO) applications, including biofuels and methanol variants. It features a turbocharging system with constant pressure, jet assist, and intercooling, ensuring efficient performance across various loads. The compression ratio of 15.5:1 and maximum combustion pressure of 200 bar contribute to its robust operation. While designed for active production as of 2026, the engine has a legacy of over 290 million cumulative operating hours with the L27/38 variant. Common failures include piston ring stiction due to carbon deposits, cylinder liner scuffing from inadequate lubrication, and water contamination in the fuel system, which can lead to premature failure if not properly managed.
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