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To clarify the effect of diesel fuel properties and engine operating conditions on engine exhaust valve sticking in the cold climate, we conducted bench engine tests on 6 sample fuels using a large size construction machine engine. From the results, it becomes clear that the ignition load limits are proportion as to the fuel cetane number and that the composition of discharged tar, generated by misfiring, agrees with a heavier part of fuel distillation region. The conditions under which discharged tar stiffens were also clarified. The intensity of valve sticking has a good correlation with 50% distillation point but does not correlate with cetane number. The heavier distillation fuel caused the valve train failure by the exhaust valve sticking.

New double-lip and dual-lip crankshaft seals for heavy duty diesel engines have been developed. The very low radial-load, double-lip design, incorporating a helix pattern, has been adapted for high speed (30 m/s) application. In this development, we established that the seal speed limit was reached when lip coking was generated due to breakdown of the oil. A bonded dual-lip seal, which can endure speeds above 20 m/s, has been developed by adopting a unique ventilating system to release the negative pressure between the two lips. From this development, a new seal design concept involving PV values has been established.