A Well-to-Wheel Comparison of Several Powertrain Technologies

In order to evaluate the potential of several powertrain configurations, a well-to-wheel analysis is performed. Specifically, downsizing / supercharging and variable valve timing is examined and compared against other alternative vehicle concepts. In order to have a fair comparison, each powertrain configuration was added to a base vehicle, such that each vehicle had the same range, the same physical characteristics and similar performance. Upstream energy use and greenhouse gases were calculated with GREET 1.5a and the downstream energy use and greenhouse gases with ADVISOR 3.2.

By downsizing / supercharging and adding variable valve timing, a spark ignition internal combustion engine can have comparable downstream overall efficiency, energy use, and greenhouse gas emissions, to a Diesel internal combustion engine. Analysis of the total energy use shows that efficiency improvements for an internal combustion engine should be made on the downstream stage (engine) while efficiency improvements for electric vehicle should be made on the upstream stage (electricity generation). Also, it was found that internal combustion engines are relatively insensitive to mass change compared to improvements in engine efficiency.