A single passenger concept vehicle, Nexus, has been designed and built at the University of Saskatchewan under contract to Transport Canada. With a fuel consumption goal of 1 L/100 km at modest steady speeds, the choice of suitable small powerplants became critical. Four motorcycle-type powertrains were efficiency mapped and compared using the computer program VEHSIM. A generalized small engine model was developed and compared to actual prototype performance characteristics. Good agreement between engine models and actual vehicle performance is indicated with the largest 250 cc engine delivering 1.6 L/100 km on the road.