Turbocharging Concepts for Downsized DI Gasoline Engines 2004-01-0036
Reducing engine swept volume (so-called ‘downsizing’) offers the potential to meet future tighter CAFÉ standards and reduced CO2 vehicle emissions in Europe. In downsizing the gasoline engine, a key challenge is controlling octane requirement without sacrificing fuel economy.
The authors have investigated five alternative approaches on a turbocharged DI gasoline engine:
Conventional stoichiometric operation, with reduced compression ratio (CR)
Lean Boost DI (LBDI) with lean operation at full-load to control octane requirement while maintaining a high CR
EGR Boost with cooled EGR dilution rather than excess air to control octane requirement
Miller cycle concept, where valve-timing strategies are employed to reduce the effective compression ratio at high load
Dual injection strategies to control octane requirement
Each approach has been investigated using engine performance and vehicle simulation codes. Experimental investigations have been carried out using a 1.125L I3 multi-cylinder engine. The most promising concept, LBDI, has been further developed using the multi-cylinder engine installed in a Ford Focus C-class vehicle.