Steve Skinner reports on progress with Tier 4 Interim/Stage IIIB compliant engines
By Steve Skinner28 July 2009
In just 16-months time engines with a power rating above 130 kW will need to be Tier 4 Interim compliant in the US and Stage IIIB compliant in the European Union. In both cases, legislation demands a -90% reduction in particulate matter and up to a -50% reduction in nitrogen oxides (NOx) from current Tier 3/Stage IIIA levels.
Senior vice president of technology and chief technology officer at Volvo, Anders Larsson told iC, "We are currently fitting Tier 4 Interim engines into prototype equipment. These engines are no longer a ‘drop in' solution because you need more cooling capacity as well as exhaust after treatment, so integration has required a major design change.
"Tier 4 Interim is a major shift and you really need to be sure the technology that you go to market with is tested and validated," he said.
Georg Diderich, senior vice president of corporate management at Deutz engines said, "Up until now OEMs have been able to rely on the engine manufacturers because any issues have been ‘inside' the engine.
"Now it's necessary to redesign machines due to after treatment devices such as the catalyst and tanks for selective catalytic reduction (SCR), the burners for regenerating diesel particulate filters (DPFs) and the enhanced insulation for heat rejection. These are big issues facing equipment manufacturers.
"We don't believe the smaller manufacturers are yet properly aware of what's before them," Mr Diderich told iC. "Depending on the power range, Tier 4 Interim comes in 2011 and Tier 4 Final follows just three years later. In practical terms, an OEM needs to be ready for each tier at least two years prior to its adoption, so it's already imperative that every single equipment manufacturer is in dialogue with their engine suppliers if they hope to attain compliance and remain in business."
Perkins has already installed its exhaust gas recirculation (EGR) and DPF based Tier 4 Interim engines in gensets, wheeled loaders, excavators, backhoe loaders, telehandlers and dozers.
Ben Reed, product engineering manager said, "We've already conducted a series of back-to-back tests on equipment fitted with Tier 3 and then Tier 4 Interim compliant engines. These tests have included an under hood thermal assessment as well as readings for fuel consumption and noise. We've also checked the transient response and the serviceability.
"Following assessment in the factory, we've then put the equipment out on field tests fitted with data-loggers that collect thousands of hours of data, recording two snapshots of all the engine sensor readings every second.
"In general, we've tried to conduct a full year of field testing, amassing 3000 hours of data across the seasons to give us the most accurate picture possible," Mr Reed told iC.
Scania has adopted its XPI extra-high pressure fuel injection with SCR on its engine platforms featuring its electronic engine management system (EMS) to meet Tier 4 Interim compliance.
"Our Tier 4 Interim engines have been designed to attain Tier 4 Final compliance with minor modifications," said Dick Burger, director of commercial and industrial motors at Scania France.
"It's an expensive exercise for OEMs to fit new engines, so we've worked hard to ensure the footprint remains the same, thus easing integration and spreading cost."
The Tier 4 Interim compliant range of engines from Scania features new blocks, cylinder liners and pistons as well as common rail fuel injection operating at 2400 bar. The urea injector for the SCR system has a life expectancy of 40000 hours while the urea filter will need replacing at 1500 hours.
"I can confirm that Scania will combine EGR with SCR to meet Tier 4 Final compliance," Mr Burger told iC. "We believe that we will only require about +5% of EGR to meet the legislation so this shouldn't require any additional cooling to deal with heat rejection and we don't envisage the need for a DPF."
One reason to avoid using a DPF is that they are sensitive to sulphur in the fuel. Mr Diderich of Deutz told iC, "We need low sulphur diesel for the DPF and EGR and this represents a big challenge in many countries. Even in the US, to supply the volume of ultra low sulphur fuel that will be required is going to be a problem."
But SCR also faces issues. According to Mr Diderich, it's a more costly and complicated system to install and the distribution infrastructure for urea isn't yet in place to adequately support the solution. "Another issue relating to urea is that it freezes," said Mr Diderich. "This means you need heated pipes from the tank to the injector which adds complication and expense."
Deutz has implemented what it calls its Deutz Variable Emission Reduction Technology (DEVERT) programme, which offers a complete range of engines, electronics, hybrid technology and after treatments as modules, so that a series of modules can be fitted together to create a bespoke solution.
"DEVERT enables us to offer both EGR with DPF or SCR depending on application," said Robert Mann, senior vice president of sales, service and marketing at Deutz. "If you are in a high fuel consumption environment, it doesn't make sense to go the EGR route because the fuel consumption is greater than with the SCR solution. However, SCR is more complicated and expensive to install and end-users will have to factor in the purchase and storage of urea."
Agco Sisu Power has chosen the SCR route to compliance, and because the base engine hasn't needed modification, installation will be the same as with its Tier 3 engines.
"The space has to be arranged for the diesel oxidation and SCR catalysts which typically represent 50% and double that of the engine displacement respectively," said Juha Tervala, marketing director at Agco Sisu Power.
"With no need for a muffler, the SCR catalyst fits in its place, so the space demands are not catastrophic," Mr Tervala told iC. "We've also been able to add the urea tank to the fuel tank, and due to reduced fuel consumption, we've not had to create any additional space for that."
As well as working alongside Russian partner Concern Tractor Plant, which manufactures a range of construction and forestry equipment, Ago Sisu Power is working with a number of existing and new OEMs in relation to Tier 4 interim compliance.
Mr Tervala said, "A number of construction machinery applications are being tested with our Tier 4 Interim engines, but as yet we cannot disclose further details."
Agco Sisu Power, like Scania, believes it can attain Tier 4 Final compliance through an increased level of SCR featuring a new substrate coating (chemical reactant). "As legislation stands, we believe we can achieve compliance in 2014 without the need for a DPF, which eliminates the need for regeneration and the removal of metal oxide ash as well as making the system less susceptible to sulphur in the fuel," Mr Tervala told iC.
Cummins has found a +5% fuel efficiency improvement from its EGR and DPF solution over its existing Tier 3 engines. In a back-to-back test carried out under site conditions across a series of duty cycles, identical wheeled loaders in the 142 to 149 kW class were used to test the two engine types with both having the same power output, peak torque and rated speed.
The improved fuel efficiency of the Tier 4 Interim QSB6.7 engine was achieved without compromising machine performance. Indeed, faster engine response to load demands meant the Tier 4 Interim powered machine completed the fuel duel tests within shorter cycle times.
"The results of the test speak for themselves," said Hugh Foden, director of off-highway business at Cummins. "OEMs can expect lower operational costs and enhanced productivity from Cummins-powered Tier 4 Interim (Stage IIIB) compliant engines.
"Because we design and manufacture the complete engine system from air-in to exhaust-out after-treatment we've been able to produce a cleaner and more fuel-efficient combustion process," said Mr Foden.
In the back-to-back evaluation the same driver operated both wheeled loaders and each machine was fitted with the same bucket size and ran on equal tyre pressures to eliminate any variables that could influence the results. Fuel consumption was measured using a secondary fuel tank, which was weighed after each test to record the exact amount of fuel used.
Steven Nendick, European communications director told iC, "Cummins spends over US$ 300 million per year on research and development and a majority of that now and in the future is being spent on meeting legislation. That said, we are trying to add customer value too, and where we can we've reduced noise and improved fuel economy."
Caterpillar too has found a +5% improvement in fuel efficiency with its advanced combustion emissions reduction technology (ACERT) Tier 4 Interim engines. Fitted with double compression two stage turbo chargers for low speed response and maximum top-end power, the engines adopt water-cooled EGR and feature 2000 bar common rail fuel injection.
Product marketing manager, Alistair Dennis said, "In our C7.1 ACERT engine for example, torque is up +30% on our Tier 3 variant. Because of the increased power density, we believe that OEMs will move down to smaller engine sizes to liberate space for the after treatment, and thus maintain a good compact machine while achieving good fuel economy."
With respect to after treatment, Caterpillar has taken a modular approach with its Cat clean emissions module. "We have a common cradle featuring the air cleaner, the muffler, and in a single can the diesel oxidation catalyst and the DPF featuring active regeneration," Bob Christmas of Caterpillar's marketing and product support division told iC.
"There are multiple configurations to the module to increase flexibility," said Mr Christmas. "Furthermore, the size of the module will not change for Tier 4 Final, so the switch in 2014 should be relatively easy."