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Background information on TIER 4 final


Exhaust gas regulation – Legal situation

The current exhaust gas regulation defines permissible limits for mobile work equipment for NOx, HC, CO and for soot particles. The limits in Europe, USA and Japan are considerably lower than in other regions of the world. Currently in effect are TIER 3 and Stage IIIA. Over the next few years, these limits will be significantly tightened, so that TIER 4 final and Stage IV will allow only around 10% of the current soot and NOx emissions starting in 2014. This will result in huge changes to diesel engine technology and exhaust gas equipment, especially for diesel engines with more than 55kW of output.
PS: Coming in below this magic 55kW line by downsizing would be a first way for an easier meeting of the future limits.

Exhaust gas regulation – Diesel engine technology

Today’s diesel engines generally use mechanical injection systems, frequently without turbo charging and with a single exhaust gas treatment mechanism. TIER 4 / Stage IV engines on the other hand will have, in addition to electronic control and a variable turbocharger, at least a cooled exhaust gas return. And the higher the injection pressures, the lower the NOx values! This means engines with 2000 bar and higher can be expected. Our engine specialists at Robert Bosch also expect that all these internal measures will not be enough, and that a complex exhaust gas treatment system will be required. Special attention should also be paid to the cooling system: not only will the cooling capacity dramatically increase, consistent maintaining of temperature bands is also essential, meaning high control capability of the cooling system. Controlled fan drives from Rexroth can make a significant contribution here.


Exhaust gas regulation – Exhaust gas treatment

Whereas today’s exhaust gas systems serve mainly to restrict noise, future exhaust gas treatment systems will also have to reduce exhaust gas components. Particles can be trapped using a DPF diesel particle filter, and the NOx can be treated by an SCR catalytic converter. Both techniques require not just the control devices themselves but also additional space – experts figure 40 to 50% of the size of the diesel engine itself. An optimized drive technology from Rexroth can help here to alleviate the space crunch in most cases. And for proper configuration of the exhaust gas treatment system with respect to the diesel engine and particular application, Bosch expertise is at your disposal.