NUMBER ONE
FOR COACH & BUS

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December 06 2017
By Mike Morgan

Mike is the Associate Editor at routeONE magazine has been a full-time road transport journalist for over 30 years and was routeONE’s founding editor


Diesel fights back

With the upcoming London ULEZ stoking calls to outlaw diesel, Cummins provides a timely reminder of the Euro 6 air quality improvements. Mike Morgan reports

In response to the growing concern over air quality Cummins has launched a clean diesel repower initiative to replace the engine and exhaust aftertreatment in older buses with a fully certified, very low emissions Euro 6 system.

Principally aimed at London, though with more than half an eye on the moves to introduce Low Emission Zones in other cities, the repower upgrade will enable pre-Euro 6 legacy buses to continue operating when the Ultra Low Emission Zone (ULEZ) takes effect in April 2019, improving the air quality of the capital and lowering the carbon footprint of the fleet.

One of the first repower projects is nearing completion at Millbrook Special Vehicles, with a 2009-built Euro 5 London double-deck receiving the latest Cummins B6.7 Euro 6 system. This also incorporates a new ZF transmission, new cooling pack and replacement electric ancillaries such as fans and power steering.

Testing of the bus is now underway with initial results demonstrating higher fuel efficiency and improved drivability due to higher torque delivery from the upgraded engine. 

The difference is under the bonnet where repower makes RM Euro 6 compliant

Upgrading the Euro 6-powered ADL Enviro 400 double-decker built in 2007 to the latest Euro 6 2017 standard also reduces particulate matter (PM) emissions by almost 90% and nitrogen oxides (NOx) by 50%, while it typically extends the life of the bus in London service by up to eight years.

The Cummins repower has an integral Stop/Start system to eliminate fuel used during idling. This can further reduce the fuel consumption of a double-deck London bus by up to 8% when operating on a duty cycle of up to 16 hours per day.

Compared to an earlier Euro 5 conventional double-deck bus, the Euro 6 fuel saving can reduce the operating cost in the range of £1,500 to £2,500 per year, making a significant impact to offset the cost of the repower, says Cummins. The lower fuel consumption also reduces the carbon footprint of the bus, with the potential to eliminate around four-six tonnes of carbon dioxide (CO2) emissions each year from the vehicle.

“The Cummins repower initiative is intended to rapidly increase the number of Euro 6 powered city buses on the road and make a significant contribution to improve air quality and reduce carbon emissions as London and other cities move to establish Ultra Low Emission Zones,” says Ashley Watton, Cummins Director — On-Highway Business Europe. 

The Cummins repower initiative aims to rapidly increase the number of Euro 6 powered buses and make a significant contribution to improve air quality and reduce carbon emissions as London and other cities move to establish Ultra Low Emission Zones

Proof of the concept was established in a most unlikely way when former Commissioner of Transport for London Sir Peter Hendy CBE approached Cummins in 2015 to repower his privately-owned Routemaster RM1005.

The 1962 RM has since gained something approaching celebrity status as the oldest bus to be Low Carbon certified. It has attend several industry events and recently spent a month on Transport for London (TfL) heritage route 15.

Mr Hendy, who attended Cummins’ launch event in London last Friday (1 December), speaks in glowing terms about the improved fuel consumption and performance. A built-in bonus is the ability to view engine status online using Cummins Connected Diagnostics, with the system sending an instant email notification when a fault occurs, together with recommended action.

Both B4.5 and B6.7 come with exhaust aftertreatment commonality

Although the RM repower could be dismissed as an interesting sideshow, it serves to highlight what can be achieved at a time when urgent action needs to be taken to upgrade the London bus fleet before all-Euro 6 compliance is enforced.

Although new Euro 6 buses are entering service, the rate of replacement means that fleets must continue to operate legacy buses compliant to earlier, much less stringent Euro 3, 4 and 5 emission regulations. Currently just 2,742 of London’s 9,600 buses are Euro 6.

Using either the four-cylinder B4.5 with ratings from 150-210hp (112-157kW) or six-cylinder B6.7 engine with top rating of 300hp (224kW), the Cummins repower system is fully compliant to the most stringent Phase-C level of the Euro 6 standards. These mandates a useful emissions life of up to 700,000km for the bus and requires extremely rigorous on-the-road emissions testing. An On-Board Diagnostics (OBD) control system is required to alert the operator if a fault may cause emission thresholds to be exceeded. Both engines use the same integrated Diesel Particulate Filter-Selective Catalytic Reduction (DPF-SCR) system manufactured alongside the engines at Cummins’ Darlington plant. 

With a very high population of Cummins-powered buses in operation both in London and around the country, the emerging Euro 6 repower opportunity spans many different models and emissions levels. Depending on the age and condition of the bus, each repower project will be individually evaluated, with some requiring a simpler engine-aftertreatment replacement, while others may need a complete powertrain refurbishment and fabrication work – with various levels of upgrade in-between.

The repower installation will be developed in collaboration with Cummins and pre-certified with an Installation Quality Assurance (IQA) to the same level as a new vehicle design installation. This involves a rigorous audit to demonstrate emissions compliance and effective design integration with the bus interfaces. 

routeone Comment 
At a time when politicians are being swayed by ill-judged reaction to pollution from diesel vehicles it is right that the relatively clean credentials of Euro 6 should be talked about; in particular the virtue of repowering Euro 6 and 5 buses as a cost-effective alternative route to improve air quality. 

It’s an opportunity that, as a major supplier to the bus market, Cummins has been quietly preparing for. Its repower technology can make an immediate impact by reducing the most emissions for the lowest investment cost, while extending the useful life of the vehicle.

The results are impressive – upgrading a Euro 4 bus to Euro 6c reduces emissions by over 70% and improves fuel efficiency by up to 8%.



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