To give a driver good drive feel, an engine is typically sized relative to vehicle weight using design parameters of other components, such as, for example, torque converters, transmission gear ratios, and manifold volume. In particular, manifold volume plays an important role in drive feel since when a driver requests and increase in wheel torque, conventional stoichiometric engine controls cannot instantly provide this wheel torque since these conventional engine control systems control engine torque primarily through control of a throttle. Thus, the engine must be somewhat oversized so that the driver has acceptable vehicle launch performance despite delays due to manifold volume, where vehicle launch refers primarily to operating pedal engagement at low vehicle speeds.
The inventors herein have recognized a disadvantage with the above approach. In particular, when an engine is somewhat oversized, fuel economy decreases due to excess weight of the somewhat oversized engine. Prior approaches for increasing an engine power to weight ratio, such as supercharges, still suffer from disadvantages due to torque increase delays, and therefore cannot improve initial vehicle launch feel.