Cleaner image

Introduction of successive new engine emissions regulations for off-highway equipment has resulted in waves of new construction equipment launches as manufacturers reconfigure their machines. Last year's adoption of the European Stage IIIA and US Tier 3 laws on 1 January 2006 for the 130 to 560 kW powerband has been no exception.

Many manufacturers used last April's Intermat exhibition in Paris, France to debut their new Stage IIIA/Tier 3 powered machines. This year it is the turn of engines in the 75 to 130 kW and 19 to 37 kW powerbands to comply and will probably result in a large number of new compact construction equipment launches at this April's Bauma exhibition in Germany.

But for engine manufacturers Stage IIIA is old news and most are already focusing on the challenge of meeting European Stage IIIB. From 1 January 2011, engines in the 130 to 560 kW class will have to meet these tough new regulations. As with Stage IIIA, the laws will be phased in for other engines sizes over several years (see table).

“The challenge of Stage IIIA was to reduce the combined level of nitrogen oxide (NOx) and hydrocarbons (HC) by -40%,” said John Deere Power Systems external product development and application manager Howard Gerwin. “The move to Stage IIIB varies slightly from powerband to powerband but the main change is the reduction in particulate matter (PM).”

The key to reducing HC and NOx emissions to meet the Stage IIIA limits for most manufacturers has been reducing the temperature of combustion and improving the actual combustion process. But some manufacturers have been able to achieve Stage IIIA compliance without resorting to electronic engine management systems on all engines.

One of the simplest ways of reducing the combustion temperature is by charge air cooling which involves lowering the intake air temperature. “The lower air temperature not only reduces the formation of NOx, it also improves engine durability and increases low speed torque and power density,” explained Mr Gerwin.

Changes to the design of cylinders and pistons and how the fuel is introduced can also help to lower the combustion temperature. The shape of the cylinder and the piston influences the 'swirl' or 'turbulence' of the air in the cylinder and can be used to optimise the completeness of the combustion. Premixed compression ignition, multiple fuel injection and common rail systems are also used to increase the fuel pressure to produce a more efficient combustion.

Many Stage IIIA engines feature exhaust gas recirculation (EGR) systems which route a measured amount of exhaust back into the intake manifold and mixes it with the incoming fresh air. This removes some of the oxygen from the intake air and lowering the combustion process to reduce the formation of NOx.

“The new Stage IIIA compliant engines are often more fuel efficient that their Stage II counterparts,” said Mr Gerwin. “But for many manufacturers, meeting Stage IIIB is going to be more a challenge than Stage IIIA and is going to call for more cooperation between engine producers, OEMs and construction equipment manufacturers.”

Engines in the 130 to 560 kW powerband will be the first to be affected by the Stage IIIB regulations, which will be introduced from 1 January 2011. The new regulations call for NOx to be cut to 3,5 g/kWh, HC to 0,19 g/kWh and particulate matter (PM) to be cut from the Stage IIIA level of 0,2 to 0,025 g/kWh.

“Particulate traps are likely to be the most common way to meet the reduction in PM needed to meet both Stage IIIB and Stage IV,” said Mr Gerwin. “But at present traps to suit construction equipment are not readily available, so it is very uncertain at the moment about how big they will be, how much they will cost and how often they will need replacing. Resolving issues like this will call for more liaison through the supply chain.”

Particulate traps may not resolve the problem completely, so electronic control may become more widespread as engine manufacturers attempt to further increase the fuel pressure and improve mixing. EGR and turbo charging may also become more commonplace.

“Achieving Stage IV calls for a further -80% reduction in NOx, which will bring emissions in line with those produced by on-road trucks,” said Mr Gerwin. “Reducing NOx to these levels will probably call for some form of after-treatment.

There are several catalyst options but these have a significant impact on fuel economy.

“The alternative is a urea-based additive which when mixed with exhaust gases, converts the NOx to oxygen, nitrogen and water. This technique would not impact on fuel efficiency but needs a urea tank, pumps and a control system. It also relies on the operator to re-fill the tank on a regular basis.”

Volvo Construction Equipment president and chief executive Tony Helsham believes that construction equipment manufacturers without their own engine development capabilities will find it difficult to meet the more stringent guidelines. “Engines will be key for strategic advantage in the future,” said Mr Helsham. “It is becoming increasingly important to properly integrate the engine with the rest of the power train to unlock the full functionality of the machines they are fitted in.”

Alternative Power

While the main focus of engine manufacturers is meeting new emissions regulations, the issue of greener fuels and alternative power sources is also coming under the spotlight.

New Holland has launched a prototype for a 7 tonne Hybrid hydraulic excavator, which has been jointly developed with Kobelco. The Hybrid is powered by a 20,5 kW diesel engine – almost half the size of the 40 kW engine which powers New Holland's conventional 7 tonne excavator – and an electric motor.

According to New Holland, the electric motor allows use of a smaller diesel engine that helps to reduce fuel consumption and carbon dioxide emissions by -40% compared to standard machine. A company spokesman told CE, that the Hybrid has undergone field tests in Japan which suggest the machine has the same digging performance as a conventionally powered machine.

Volvo's work on hybrid power solutions is more concentrated on heavy vehicles, such as trucks, buses and larger construction equipment. Nonetheless, the company claims that hybrid power could offer fuel savings of around +35% and also lower maintenance costs through reduced wear on the braking system.

By using the diesel engine and electric motor in parallel, Volvo claims its I-SAM (Integrated Starter, Alternator Motor) system offers substantially more power than series hybrids. I-SAM is a combined starter motor, drive engine and generator, which works with an automatic converted mechanical transmission, an electronic control unit, diesel engine and batteries that are charged by breaking energy.

According to Volvo, I-SAM provides enough power to start and accelerate heavy vehicles without assistance from the diesel engine, significantly reducing noise levels. For on-highway engines the weight of the batteries has been a restriction on wider adoption of the technology but for off-highway construction equipment, the added weight could prove to be a bonus. “Intellectually it's not difficult to imagine batteries replacing the counterweight on a wheeled loader. We think fuel savings of up to +50% might be possible,” said Mr Helsham.

Rising oil prices mean that engine producers and construction equipment manufacturers are also looking at alternative fuels, such as biodiesel, which is produced from vegetable based oils.

Case has approved use of B5 blends (5% biodiesel and 95% petroleum based diesel) in all of its mechanical engines. B20 blends can also be used in most of its engines, except electronic versions and those used in the 410 and 420 skid steer loaders.

Sisu Diesel has gone step further and approved use of B20 in common rail engines and B100 in engines which do not feature common rail injection. Sisu Diesel has said that its engines do not need to be modified to use biodiesel but recommends that the engine oil, oil filter and fuel filter are changed twice as often as required by the normal service interval.

Mr Gerwin said, “We are life testing engines fuelled by biodiesel formed from 5% rape seed oil and diesel at the moment but we are also other fuels, such as pure ethanol and liquid gas formed from biomass or gas.”

New Power

The phased introduction of Stage IIIA means that a number of engine manufacturers have presented new units in the 75 to 130 kW and 19 to 37 kW powerbands over the last 12 months.

According to Perkins industrial marketing director Chuck Wills, much of the research and development carried out for the first phase of Stage IIIA could be directly applied to the second phase. “The emphasis is more on making the engines better in terms of performance, productivity and refinement,” he said. “We have focused on delivery of greater power density – more power from the same sized package – to allow OEMs to drop in the new engines without re-engineering their machines.”

Perkins applied this philosophy to its Stage IIIA compliant 1104D series engines, which have retained the same size as the Stage II versions but now offer up to 106 kW of power. Both mechanical and electronic versions of the engines are available and, Mr Wills claims that, the four cylinder units deliver power equivalent to a six cylinder engine.

Deutz has added a Stage IIIA compliant four cylinder engine to its 2013 series, which offers a maximum power output of 129 kW. The new common rail engine is available in three formats. The electronically and mechanically controlled versions, offer 129 and 104 kW, respectively, and are equipped with charge air coolers and turbochargers. The basic 75 kW version does not feature charge air cooling.

Cummins' 82 kW output QSB3.3 engine uses electronic control and common rail, along with in cylinder design changes, to meet Stage IIIA regulations rather than using EGR. According to Cummins, the design of the 3,3 litre unit offers performance equivalent to a 4,5 litre engine but with the advantage of being -30% lighter.

The engine is available in four other power ratings – 60, 63, 71 and 74 kW – which are already meet Stage II regulations and will gain Stage IIIA approval before 1 January 2008.

Caterpillar's 4,4 litre engine is also available with either mechanical or electronic control. The four valve per cylinder electronic version is available with either a turbocharger or an air-to-air aftercooler and offers outputs of between 62 and 106 kW. The mechanically controlled C4.4 engine features two valves per cylinder and can be specified as a naturally aspirated, turbocharged or air-to-air cooled unit. The mechanical version offers power outputs of between 52 and 74,5 kW.

But some of the launches also fall into the 130 to 560 kW powerband. One of the largest new engines is John Deere's PowerTech Plus 13,5 litre engine, which is the largest in the four model range and offers 261 to 448 kW of power. “The Plus range has been developed to offer better power characteristics than the electronically controlled PowerTech E and mechanically controlled PowerTech M engines,” said Mr Gerwin.

Finland-based Sisu Diesel has also launched the Stage IIIA compliant Citius series engines, which are available in three, four or six cylinder configurations.

The three model series offer maximum power outputs of between 125 to 309 kW and use pilot injection to minimise combustion noise and feature a new timing gear design to minimise mechanical noise.

Compact Solutions

Lower down the power range Perkins and Deutz have all unveiled new engines in readiness for this year's phase of the Stage IIIA emissions regulations. Perkins' 400D series offers power outputs in the 8 to 49 kW range while Deutz's naturally aspirated 2008 series produce up to 27 kW.

The higher power rated Deutz 2009 series are also available as a naturally aspirated unit with three or four cylinders but the four cylinder version can also be specified with a turbocharger. The 2009 series deliver between 28 and 53 kW, depending on the specification.

The Next Phase

Most engine manufacturers appear to be ready for the next phases of Stage IIIA, which are likely to result in further waves of machine launches at this year's Bauma and ConExpo in 2008.

Many engine producers are already looking at the options for developing, if not already testing Stage IIIB compliant engines. But fitting additional filters, tanks and catalytic converters into machines is likely to provide construction equipment manufacturers with a challenge over the next few years.

But is it possible to reduce engine emissions any further? John Deere's Mr Gerwin said, “Between introduction of Tier 1 in 1996 and Stage 1 in 1999 and Final Tier 4 and Stage IV, NOx, HC and PM will have been reduced by 99%.” Mr Gerwin declined to comment on whether the technology exists to meet a Stage V. But he added that he expected to see Stage IV engines further refined to compensate for the loss of fuel economy that would be inevitable in meeting the next set or regulations.