Scania introduced Euro 4- and Euro 5-compliant diesel bus engines at the biennial UITP (Union International des Transport Public). (Related post.) Euro 4 becomes mandatory in October 2006 and Euro 5 in October 2009.
Scania’s 9-liter, 5-cylinder Euro 4 and Euro 5 bus engines use EGR (exhaust gas recirculation) to reduce emissions to the required level. The company so far has sold some 2,000 Euro 4 trucks with Scania EGR.
EGR is a well-established technology used on diesel-powered cars and light commercials all over the world, as well as on heavy commercial vehicles sold in the North American market every year. EGR reduces the combustion temperature, which in turn reduces the formation of nitrogen oxides (NOx).
Scania’s approach to EGR takes out a portion of the exhaust flow—up to 18% for Euro 4 and 25% for Euro 5—before the turbocharger and cools it with the engine coolant before blending with the intake air. The challenge consists in feeding exhaust gases into the intake air, which has a higher pressure.
Scania has solved this with a patented venturi system. The Scania venturi is a constriction in the intake manifold that makes the compressed intake air travel faster. This creates a low-pressure area downstream of the constriction, which is used to “suck” the exhaust gases into the intake air. A simple valve system is used to regulate the flow in relation to engine load.
The engines use high-pressure fuel injection in combination with a maintenance-free oxidizing catalyst to reduces particulates and eliminates the diesel smell.
An maintenance-free particulate filter (optional on Euro 4 models) can be integrated into the normal silencer. Being a part-flow design, the filter effectively halves particulate emissions, while simultaneously eliminating the risk of clogging. The filter is standard on Euro 5 engines.
The Euro 4 and Euro 5 families of bus engines are both based on a 9-liter, 5-cylinder unit. Euro 4 bus engines will be available from November 2005. Euro 5 engines and particulate filters are scheduled to become available during 2006.
|Scania Euro 4 Bus Engines|
|230 hp (172 kW)||1,050 Nm (774 lb-ft)|
|270 hp (201 kW)||1,250 Nm (922 lb-ft)|
|310 hp (231 kW)||1,550 Nm (1,129 lb-ft)|
|Scania Euro 5 Bus Engines|
|270 hp (201 kW)||na|