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The characterization and operation of engines for hybrid-electric vehicles are reviewed with special attention being given to on-off engine operation and its effect on vehicle fuel economy and emissions. Rotary, two stroke, and gas turbine as well as four stroke gasoline and diesel engines are considered for hybrid applications. Various engine operating strategies are evaluated for range-extender and engine-electric series hybrid vehicles based on simulation results. The need for on-off engine operation to attain good fuel economy and low emissions in city driving is identified for series hybrids designed for unlimited range at highway speeds. Previous experience with the GE/JPL HTV-1 parallel hybrid vehicle in 1980-82 is reviewed as that vehicle successfully utilized on-off engine operation.

Comparisons have been made between data obtained from dynamometer tests of various electric vehicles and computer simulations of the same vehicle-battery combinations for several driving cycles. The vehicles included in the study were the ETV-1, Bedford Van, Unique Mobility, ETX-1, and DSEP(TB-1). The batteries studied were the ALCO 2200, Gel/cel 3, EV5T, ETX-100(CHL12), and the NIF-170. The comparisons indicated that the energy consumption values obtained using ELVEC agree within 10% with test data for both constant speed and variable power driving schedules. The range comparisons were less consistent, but the predictions agreed with the data to within 10% if the vehicle battery was in good condition and the controller did not limit battery power at low states-of-charge.