Abstract
Offsetting a crankshaft in the thrust side is adopted to some of gasoline engines is one of the schemes for fuel economy. Offsetting a crankshaft causes an improvement of combustion and a reduction in piston friction losses, but it also causes a geometrical change in the angle between a crank-arm and connecting-rod, and the efficiency of changing the force acting on a piston to engine output torque may change. The effect of offsetting the crankshaft in both the thrust and anti-thrust side on indicated mean effective pressure (IMEP), piston friction losses and engine output torque was investigated in a diesel engine. It was found that offsetting in the thrust side caused a reduction of piston friction losses. Under the higher engine speed, offsetting in the thrust side was effective for improving IMEP and an increase in engine output torque was showed. However, under the lower engine speed, no improvement of IMEP was found by the offsetting in the thrust side, and engine output torque improved by offsetting in the anti-thrust side.
