Downsizing a Gasoline Engine Using Turbocharging with Direct Injection 2003-01-0542

Nowadays, downsizing (reduction of the engine size) appears as a major way of improving fuel consumption of spark ignited engines while maintaining the advantage of the low emission capability of three ways catalytic system. The downsizing approach with turbocharged applications is now more and more oriented towards fuel economy, thanks to dedicated solutions. The use of gasoline direct injection system coupled with adapted turbochargers provides several ways of enhancing engine knock resistance especially at high load and low engine speed where existing PFI turbocharged engines are still limited.

The purpose of this paper is to highlight the combustion behaviors of the new generation of turbocharged direct injection engines and to demonstrate the potential of such a solution on a specific application. First, we explain the global system approach (injection, turbocharger, fluid motion, valve timing …) used to reach the necessary goals: high low end torque and specific power capabilities and low specific fuel consumption over the whole engine map. Then, we present all the results at part load and full load obtained on the Renault basis 1.8l IDE concept modified by IFP for a turbocharged application. This engine allows to take advantage of its high knocking limit in order to replace a 3.0 liter naturally aspirated engine and thus to have a fuel consumption benefit of more than 15% with at least the same acceleration performance. At full load, the specific fuel consumption is less than 300 g/kWh over the whole engine speed range with a BMEP of 2.0 MPa over 1500 rpm and a power density of 83 kW/l with a fixed compression ratio of 10.3:1.