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Improvements of vehicle fuel economy may be achieved by the introduction of advanced internal combustion engines (ICE) improving the fuel conversion efficiency of the engine and of advanced power trains (PWT) reducing the amount of fuel energy needed to power the vehicle. The paper presents a novel design of a variable compression ratio advanced spark ignition engine that also permits an expansion ratio that may differ from the compression ratio hence generating an Atkinson cycle effect. The stroke ratio and the ratio of maximum to minimum in-cylinder volumes may change with load and speed to provide the best fuel conversion efficiency. The variable ratio of maximum to minimum in-cylinder volumes also improves the full load torque output of the engine.

Current flexi fuel gasoline and ethanol engines have brake efficiencies generally lower than a dedicated gasoline engines because of the constraints to accommodate a variable mixture of the two fuels. Considering ethanol has a few advantages with reference to gasoline, namely the higher octane number and the larger heat of vaporization, the paper explores the potentials of dedicated pure ethanol engines using the most advanced techniques available for gasoline engines, specifically direct injection, turbo charging and variable valve actuation. Computations are performed with state-of-the-art, well validated, engine and vehicle performance simulations packages, generally accepted to produce accurate results targeting major trends in engine developments. The higher compression ratio and the higher boost permitted by ethanol allows larger top brake efficiencies than gasoline, while variable valve actuation produces small penalties in efficiency changing the load.

Improvements of truck fuel economy are being considered using a flywheel energy storage system concept. This system reduces the amount of mechanical energy needed by the thermal engine by recovering the vehicle kinetic energy during braking and then assisting torque requirements. The mechanical system has an overall efficiency over a full regenerative cycle of about 70%, about twice the efficiency of battery-based hybrids rated at about 36%. The technology may improve the vehicle fuel economy and hence reduced CO₂ emissions by more than 30% over driving cycles characterized by: frequent engine start/stop, vehicle acceleration, brief cruising, deceleration and stop. The paper uses engine and vehicle simulations to compute: first the fuel benefits of the technology applied to passenger cars, then the extension of the technology to deal with heavy-duty vehicles.

The introduction of advanced internal combustion engine mechanisms and powertrains may improve the fuel conversion efficiency of an engine and thus reduce the amount of energy needed to power the vehicle. The paper presents a novel design of a variable compression ratio advanced spark ignition engine that also permits an expansion ratio that may differ from the induction stroke therefore generating an Atkinson cycle effect. The stroke ratio and the ratio of maximum to minimum in-cylinder volumes may change with load and speed to provide the best fuel conversion efficiency. The variable ratio of maximum to minimum in-cylinder volumes also improves the full load power output of the engine. Results of vehicle driving cycle simulations of a light-duty gasoline vehicle with the advanced engine show dramatic improvements of fuel economy.