During development of the 2014 model-year Accord Hybrid, for which the SPORT HYBRID i-MMD new model hybrid system was adopted, 2nd-order vibration transmitted to the steering became an issue. This occurred because the vehicle has higher engine net torque than a gasoline engine vehicle, so that there is larger crankshaft revolution 2nd-order fluctuation, which is the source of the vibration. There is concern that using only reduction of engine net torque as the means to lessen crankshaft revolution 2nd-order fluctuation could cause an increase in the brake-specific fuel consumption. Therefore the combustion control parameters, such as ignition timing and valve operation timing, were changed as a way of optimizing crankshaft revolution 2nd-order fluctuation, engine net torque, and brake-specific fuel consumption. These measures achieved the steering vibration target while also determining the optimal point where the amount of engine net torque reduction could be lessened by 5 Nm and 1% of the increase in brake-specific fuel consumption could be recovered.
Article of Honda R&D Technical Review Vol.26 No.2 (144 - 150)