Cummins ready for Euro 6
Instead, the thrust of EU legislation is likely to change and concentrate on bringing down CO2. “Euro 6 has resulted in such tough emission limits that it would be very hard to make them any stricter,” Williams observes.
He was speaking at the press unveiling at the Cummins plant in Darlington of the company’s mid-range Euro 6 engines suitable for bus and coach applications. In order to meet the new limits the ISB 4.5-litre and ISB 6.7-litre both use a combination of Selective Catalytic Reduction (SCR) and cooled Exhaust Gas Recirculation (EGR) technology as well as a particulate filter.
The filter will self-generate when required without the need for driver intervention but will require cleaning every 200,000kms. The aftertreatment system is designed to continue to operate efficiently even at the low exhaust temperatures experienced by city buses.
Neil Pattison, Cummins director, automotive engine business, for Europe, the Middle East and Africa insists that operators are unlikely to suffer a fuel consumption penalty if they opt for the new engines.
“We’ve closely balanced the EGR and SCR systems to meet the regulated NOx levels,” he says. “That allows us to optimise the fuel economy and AdBlue usage for the lowest-possible running costs.
“We expect AdBlue usage will fall from 5 to 7 per cent of diesel consumption at Euro 5 to 2 to 3 per cent of diesel consumption at Euro 6 depending on the duty cycle,” he adds.
There will be a weight penalty says Pattison, albeit a modest one – around 40kg for the 4.5-litre and approximately 60kg for the 6.7-litre – once all the emission suppression equipment is taken into account. And while pricing policy is a matter for the manufacturers who use these engines to power their products, there seems little doubt that customers will have to stump up more. Manufacturers fitting Cummins products include ADL, VDL, Wrightbus and Optare.
Steeper prices should not come as a shock given the amount of work engine builders have had to put in to meet Euro 6, says Pattison.
The latest standard sees particulate levels down by 50 per cent with NOx – oxides of nitrogen – cut by 77 per cent.
“However because a change in legislation means that the way particulates are measured has been altered from weight to unit count, in real world terms particulate levels have been reduced by closer to 99 per cent,” Pattison points out. “That has been a significant challenge for all manufacturers to meet.
“Indeed Euro 6 is the most challenging piece of emissions legislation to date, with exhaust emissions moving to near-zero levels.”
Fitted with a variable geometry turbocharger optimised for high torque and low speed capability – exactly what is required by buses on stop/start urban work – the new 4.5-litre has a maximum power output of 200PS and produces up to 760Nm of torque. Although it has been designed and developed in the UK, it is being built in a £267million factory in Beijing, China, set up by Cummins in a joint venture with local manufacturer Beiqi Foton.
With a block 10 per cent lighter and a head 20 per cent lighter than the previous ISB 4.5-litre, used widely in hybrid buses as well as in mainstream vehicles, the four-cylinder unit is said to offer improved coolant flow and cylinder pressure capability with reduced noise, vibration and harshness.
The engine’s design has been influenced by that of the ISF 3.8-litre with the combination of cooled EGR and a variable geometry turbo a consequence of the work Cummins has done to meet the USA’s EPA 2010 emission requirements: Washington’s equivalent to Euro 6.
Designed along much the same lines as its smaller stable-mate, the six-cylinder 6.7-litre produces up to 280PS in buses, rising to 310PS in coaches. Maximum torque is 1,100Nm in both cases.
Both engines will run on up to 20 per cent biodiesel. As far as higher concentrations are concerned much will depend on the feedstock used, says Cummins.
A significant change as far as Euro 6 is concerned is the European Union’s decision to introduce in-service testing either in roadside checks or as part of the annual MoT test using portable emissions measurement systems to ensure engines remain compliant with the regulations during the so-called ‘useful life’ of the vehicle. Useful life is deemed to end at seven years/700,000kms, a point at which many buses are still giving sterling service and are set to do so for many years to come.
Exhaust emissions are not allowed to exceed 1.5 times the laboratory emission level during this useful life and will be monitored by a much more demanding OBD (On-Board Diagnostic) system which will measure emissions continually.
A particulate emissions threshold will be introduced for the first time along with tougher NOx and anti-tampering limits and an AdBlue quality sensor.
Because tuning the engine and the aftertreatment system to meet the OBD requirements is a lot more complex than anything encountered under Euro 5, the maximum limits will not be introduced immediately but instead phased in gradually from 2013 to 2015.
What happens once the engine’s ‘useful life’ comes to an end? “It looks as though an allowance will be made for a degradation in emissions but to be honest this remains a grey area,” says Williams.
Manufacturers will be obliged to publicise widely the repair and maintenance information required to ensure emissions and OBD compliance, a requirement which should benefit independent workshops, not to mention in-house workshops run by bus and coach operators themselves.