Combining High Performance with Euro IV Capability in a Naturally Aspirated Production Engine

The requirements to produce high specific power, a high torque across a broad engine speed range and very low emissions levels have been seen as mutually exclusive in a conventional normally aspirated SI engine. Ford Motor Co in association with Cosworth Technology Ltd. have developed a port injection SI engine which achieves in excess of 63kW/ltr, a peak torque in excess of 97Nm/ltr, 92Nm/ltr between 2500rpm and 6500rpm and meets European IV and North American LEV emissions levels for the Focus ST170 in Europe and the SVT Focus in the US.

To achieve the required torque across the speed range the volumetric efficiency needed to be maximized at all engine speeds. This was done by fitting continuously variable inlet valve timing, variable length intake manifold and a tuned exhaust manifold. To meet the emissions requirements, the catalyst light off time must be kept to a minimum. This was accomplished by ensuring that the engine had stable combustion when run from cold with retarded spark advance. Stable combustion when cold and a high level of flow to meet the performance targets was made possible by careful optimization of intake port flow and tumble characteristics and VVT strategy. The tuned exhaust manifold and catalyst location improved engine efficiency and was able to meet the emission targets by use of the latest tri-metal coating and metal substrates. To ensure the maximum performance was obtained from each cylinder at all times, individual knock sensing was also utilized.