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Hino Motors has developed the new K13C, a 12.9 liter six cylinder in-line, heavy duty diesel engine that provides superior fuel consumption, extra low noise and excellent driveability together with a lower exhaust emissions. The initial K13C engine, whose production began in 1986 and about 30,000 units have been produced, is recognized all over the world for its good reliability and fuel economy. The new K13C is using the basic design and manufacturing/assembly processes of the previous one but includes a common-rail type fuel injection system with enhanced electronic controls to meet future regulation and customer requirements. Major design changes consist of a new cylinder head, a new front gear train, a new air intake system, a new turbocharger, a new compression brake system and electronic control module. The optimization of the intake system includes a new intake port and an electronically controlled inertia charging system.

This paper describes some of the advanced technologies designed for low fuel consumption in the new P11C in-line 6-cylinder, heavy duty diesel engine which has two power ratings of 239kW at 2100rpm and 221kW at 2150rpm. The new engine's displacement has been increased from 8.8 liters of the base engines (EP100, P09C) to 10.5 liters without an increase in either engine weight or overall dimensions. The turbocharger has a mixed-flow turbine which improves the fuel consumption by improving the turbine efficiency. The piston, made from ductile cast iron, improves the fuel consumption and reduces the exhaust emissions by heat insulation of the combustion chamber (i.e. the ductile cast iron has a lower thermal conductivity than the previous piston's aluminum alloy). Additionally, this engine achieves lower friction loss by an intake air system with low air flow resistance and by roller cam followers.

In heavy duty vehicles, a higher boost and/or smaller sized diesel engine is quite effective in achieving fuel economy. However, this causes an increase of pumping loss due to increased intake air and exhaust gas flow of the engine at high load and high speed conditions. It also causes a relatively poorer torque at low speed conditions due to a lack of boosted air. The authors investigated the pumping loss and volumetric efficiency of a high boosted turbocharged diesel engine and analyzed the effects of the turbocharger, inertia charging and the valve opening areas. An optimization of small geometry turbine housing was obtained for the improvement of both low speed torque and fuel economy. The effects of inertia charging were ascertained from the relation between engine valve timing and the amplitude and phase of intake air pulsation. Increasing the intake and exhaust valve opening area improved fuel consumption by reducing pumping loss.