The start of 2012 marked the introduction of another tranche of emissions legislation in Europe and the US - an extension of the EU Stage IIIB and US Tier 4 Interim laws that came into force at the start of 2011 for the 130kW to 560kW power band.
As of 1 January this year, the strict emissions limits - which call for a 90% reduction in particulate matter (PM) along with a 50% drop in nitrogen oxides (NOx) - also apply to the 56kW to 129kW power categories.
While these laws have prompted a flurry of new launches over the last 12 months, engine manufacturers already have their sights set on the Stage IV/Tier 4 Final requirements that will come into force from 2014.
These laws take emissions down to near-zero levels - in fact, some manufacturers say that in certain areas and inner cities, the requirements are so strict that their Tier 4 Final engines will act as air cleaners.
Engines rated between 130kW and 560kW will be affected in 2014, and the 75kW to 129kW power band will have to comply from 2015.
To achieve this next step, engine manufacturers will have to use all the tools in their emissions reduction armoury. Depending on the engine size, this could mean a combination of cooled exhaust gas recirculation (EGR), selective catalytic reduction (SCR) and diesel particulate filters (DPFs).
EGR has certainly proved the most popular approach for construction machinery in terms of meeting the 2011/2012 limits. In the EGR camp are major engine manufacturers including John Deere, Volvo, Caterpillar and Perkins whose Stage IIIB/Tier 4 Interim offerings each included DPFs.
Rivals JCB and Cummins opted for EGR designs without using DPF or regeneration burners for engines below 129kW. Instead they managed to control emissions with careful management of the combustion process. Cummins' larger (130kW to 560kW) engines, however, use a DPF.
Meanwhile, Tognum subsidiary MTU Friedrichshafen decided to use SCR technology for Stage IIIB/Tier 4 Interim on engines below 560kW, and EGR for engines from 560kW to 730kW. Agco Sisu and Scania have both pursued the SCR approach to comply with Stage IIIB/Tier 4 Interim regulations.
Looking ahead to Stage IV/Tier 4 Final, a handful of major engine manufacturers have so far released details of their solutions.
And the models showcased to date reveal an interesting mix of technologies. Agco Sisu, for instance, is currently testing options to meet Stage IV/Tier 4 Final and envisages further developing the SCR technology it used to meet the current Stage IIIB/Tier 4 Interim legislation.
However, for the higher end of its power class, it said it would probably also need to add EGR to achieve the required NOx reduction, but the target is still to keep exhaust to be circulated at a minimum in order to minimise the requirement to increase the cooling capacity.
Diesel oxygenated catalyst
An Agco Sisu power spokesperson said, "Depending on engine type and power density, we shall have either an SCR-only solution, or SCR plus cooled EGR. In both cases we shall also have a diesel oxygenated catalyst (DOC) and air management control. The turbo technology will be also new compared with current Stage IIIB engines."
But the company will seek to avoid the use of a DPF in its Stage IV/Tier 4 Final engines. It is currently developing and testing a Stage IV/Tier 4 Final-compliant 16.8l engine with a rated power of 522kW - the largest yet in its diesel engine range - that does not use a DPF.
Meanwhile, rival Scania said it would meet the 2014 regulations by adding EGR to its SCR aftertreatment for its engines - a combination that it said was so effective it could manage without the added bulk and complexity of a particulate filter.
The manufacturer will showcase its DC09, DC13 and DC16 engines at Intermat. They range from 202kW to 515kW, and key to the design is the company's high-pressure common-rail fuel injection system and turbocharger.
The use of Scania's own engine management system is said to enable high-precision control of the combustion and exhaust aftertreatment systems.
Indeed, two features that are likely to appear on many Stage IV/Tier IV Final engines, particularly to help the lower power classes avoid having to use aftertreatment systems, are advanced combustion and fuel injection technologies - central components in Kohler's Tier 4 Final offering.
The US manufacturer worked together with its Italian subsidiary Lombardini to develop its new diesel engine series for the off-road industrial, construction and agricultural markets - the 55kW KDI2504TCR and the 42kW KDI1903TCR.
Kohler worked on the most efficient use of its direct injection system in combination with EGR and a DOC to achieved compliance with the Stage IV/Tier 4 Final laws without the need for a diesel particulate filter.
The high pressure common rail system on the engine series, which will be manufactured in Italy, uses pressures at 2,000bar, which it said would result in better atomisation of the fuel, improved fuel consumption and a reduction in emission particulates.
This technology works in combination with an engine mapping program within the electronic control unit. This monitors and manages the engine's power output by injecting fuel into the combustion cycle to maximise torque and power when needed most.
Kohler global power group president Dick Fotsch said, "The lack of a DPF is a real breakthrough for engines at these displacements, and the technology systems built into the engines by Kohler and Lombardini are what make them truly innovative at this power range."
Without the need for a DPF or bulky urea tank, the compact size of Kohler's new diesel engines offers increased compatibility and would fit existing and new equipment designed by manufacturers, according to the company.
Advanced combustion and fuel injection technologies are key elements in JCB's 55kW Ecomax engine too, which it said would also require no aftertreatment to meet the Stage IV/Tier 4 Final legislation.
JCB's Stage IIIB/Tier 4 Interim offering, the Ecomax T4 4.4l engine, also uses an EGR solution that eliminates the need for a DPF filter or any exhaust aftertreatment. This engine also uses common rail fuel injection technology with pressures of 2,000bar and variable geometry turbochargers on all but the lowest powered 55kW model.
After spending around £80 million (€93 million) developing its current generation of Dieselmax engines, JCB now plans a further £31 million (€37 million) off-highway diesel engine development project. Design and research for the new engine, which will go into production in 2016, is currently underway.
Meanwhile, Cummins, Perkins and MTU have also released some details of their Tier 4 Final/Stage IV solutions - each using either SCR and EGR/DPF technologies, or a combination of all three.
For example, MTU will showcase its newly-developed Series 1000, 1100, 1300 and 1500 C&I engines at this year's Intermat show, covering the 100kW to 460kW power range. These engines meet the upcoming emissions limits using SCR exhaust aftertreatment technology only and will need no DPFs.
The company said it would also be introducing its Series 1600 C&I engines from 2014, which will extend the range to 730kW. For these larger engines, MTU said it would use high-pressure common rail injection, two-stage turbocharging and cooled EGR, but will not require a DPF.
'Cleaner than before'
Dr Ulrich Dohle, chief technology officer at MTU's parent company, Tognum, said, "We are proud that, in the future, we will continue to be able to offer our customers engines without DPFs for all construction industry applications. They are cleaner than ever before and they use even less fuel than the current engines."
Meanwhile, Cummins' Tier 4 Final/Stage IV-compliant, 503kW QSX15 diesel engine augments the company's existing EGR and Cummins particulate filter (CPF) technologies with SCR to achieve the final reduction in NOx emissions required to meet the 2014 standards.
Cummins will showcase a line-up of 56kW to 503kW EU Stage IV and US Tier 4 Final-compliant engines at the Intermat show.
SCR aftertreatment has also been added to Cummins' 231kW QSB6.7 engine, which used a cooled EGR system and a Cummins Compact Catalyst (CCC) to meet the Stage IIIB/Tier 4 Interim emissions laws.
Both new engines are said to produce fuel savings of up to 8% compared to Tier III models, and of up to 3% compared to the Stage IIIB and Tier 4 Interim models.
Rival Perkins will also add SCR to its Stage IIIB/Tier 4 Interim solution in order to meet the Stage IV/Tier 4 Final laws. It will combine this technology with the EGR and a DPF method for its 400 series engines above 56kW.
And for engines below 56kW, Perkins is using advanced EGR technology to meet the 2014 regulations. The new 46kW 400F three- and four-cylinder engine models feature 97% of the same components from Tier 4 Interim/Stage IIIB, but include a new passive regeneration aftertreatment system to burn away the soot in the DPF.
The big names that are yet to reveal details of their Tier 4 Final/Stage IIIB solutions for construction equipment include John Deere, Volvo and Caterpillar. Since these manufacturers used the EGR and DPF solution to meet the Stage IIIB/Tier 4 Interim requirements, it will be very interesting to see whether they add further aftertreatment systems for 2014.
The tools are there. For instance, Volvo Penta - which produces engines for power generation applications - has already released its Tier 4 Final/Stage IIIB offering. It will unveil a new engine at the Intermat exhibition which uses the same SCR technology that Volvo Penta used to meet the 2011 legislation - keeping it simple for OEMs.
Indeed, it is fair to say that the new legislation has put enormous demands on OEMs who are facing the challenge of re-designing their machines to install the new engines and aftertreatment systems - the smaller the change for the construction equipment manufacturers, the better.