Automotive Engineer

Whether you’re walking around the city centre or driving on the motorway, tailpipe fumes from the many older commercial vehicles on the roads taint the air. Harmful emissions have been a cause for concern for governments for many years, and legislation to reduce them has become steadily more stringent.

The rate at which legislators have asked for reductions in harmful emissions – particularly NOx – has accelerated so quickly that engineers have found it difficult to keep up. In 1992 Euro I stated that commercial vehicles could emit no more than 8g/kWh of NOx. Four years later Euro II reduced that figure to 7g, and when Euro III was introduced in 2000 it dictated that NOx emissions could only be 5g/kWh. Particulate matter, hydrocarbon and carbon monoxide levels have also followed the same downward curve.

The leap from Euro V to Euro VI emissions levels has forced engineers to develop new processors and include more technologies to push emissions down further. From 1 January 2014 Euro VI will require trucks to emit no more than 0.4g/kWh NOx, 0.01g of particulate matter, 0.13g of HC and 1.5g of CO.

Daimler was the first OEM to meet these targets with its six-cylinder, 12.8-litre OM 471 diesel engine unveiled last year. It controls emissions using selective catalytic reduction (SCR), cooled exhaust gas recirculation (EGR) and a diesel particulate filter. The engine, which has been used in the Actros truck, has power and torque outputs of between 310kW and 375kW and 2,100Nm and 2,500Nm. 

Daimler has now expanded its Euro VI-compliant commercial vehicle engine family to include four- and six-cylinder units ranging in power output from 175kW to 315kW. The six-cylinder OM 470 uses cooled EGR, urea injection and a particulate filter, while the OM 93x series of engines also benefits from adjustable exhaust camshaft timing to support particulate filter regeneration.

Georg Weiberg, Daimler’s head of truck product engineering, says: “Legislators are exerting a lot of pressure. The upcoming Euro VI emissions standard can only be achieved with the help of very complex and costly technology. 

“Further down the road, we’ll also have to comply with CO2 legislation that will regulate fuel consumption. In addition, we increasingly have to deal with secondary conditions, such as access restrictions to inner cities.”

The engines have been developed to fulfil the needs of various applications from heavy-duty long-distance haulage vehicles to medium-duty inner-city delivery trucks and buses.

“Compared to our Euro V-compliant engines, a much greater effort was needed to achieve the Euro VI standard, requiring additional technologies such as exhaust gas recirculation,” says Weiberg.