Diesel engines power most of the world’s off-road construction equipment and produce exhaust emissions that contain some harmful pollutants such as nitrogen oxides (NOx) and particulate matter (PM).
The two world agencies driving emission standards for off-highway diesel engines are the US Environmental Protection Agency (through its Tier 4 Final regulations) and the European Union through its Stage IIIB equivalent emissions regulations for the EU member states.
These regulations take us a long way down the road to cleaner air and the elimination from diesel emissions of nitrogen oxides and particulate matter.
In terms of effect dates and emissions levels, the EPA and EU are closely aligned, with the first regulations in effect on January 1, 2011 across the 130-560kW (174hp to 751hp) power category, and requiring diesel engines to reduce PM exhaust emissions by 90 percent and NOx exhaust emissions by 45 percent compared with the old Tier 3 and Stage IIIA emissions standards.
To lessen the cost impact on manufacturers of off-highway equipment a transitional period was introduced in 2012 where manufacturers could continue to build previous generation models while designing and building new models that met the tough emission standards.
So, the final Tier 4/Stage IV regulations are being phased in over time according to engine specifications. The final deadline covering 560kW and above (751hp) is 2015.
Engines sized between 19-56kW had to meet standards by last year, however lower tier engines will remain in use in regions around the world that do not have emissions standards for off-road engines, including New Zealand.
The old technology will eventually be superseded as European and US standards drive new engines and the added technology and increasingly expensive components will add to the cost. While there are obvious fuel saving opportunities (at least five percent),and increases in power output, it remains to be seen whether the benefits will outweigh the rising cost of equipment.
Manufacturers have gone down a number of different design paths to meet regulations but have in common high pressure common–rail fuel injection (at least 2000bar) with variable geometry turbocharging and electronic engine control being equally popular standards.
Manufacturers are also commonly adopting both exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) with a urea-based exhaust additive such as AdBlue. In the past this has been an ‘either/or’ option.