Cummins has launched an initiative to replace the engine and exhaust aftertreatment in older buses with a fully certified Euro VI system. The repower would enable pre-Euro VI legacy buses in London fleets to continue operating when the Ultra Low Emission Zone (ULEZ) comes into force in April 2019, allowing older buses to continue running through the capital.
The company also claims that the repower could extend the life of such buses by up to eight years, and bring a performance upgrade with improved torque response so that the buses drive with less effort. The Cummins repower features an integral stop-start system to automatically cut the engine during idling, such as when passengers are boarding or alighting. This could 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.
Cummins also claims that reduced fuel consumption would reduce the carbon footprint of each bus, with the potential to eliminate around four to six tonnes of CO2 emissions per bus per year.
Proof of concept was established by a Cummins repower of London Routemaster bus RM1005, which first entered service in 1962 and is now fully certified to meet Euro VI emissions. RM1005 has recently operated on London Transport heritage route 15 and is Low Carbon certified with a fuel consumption of 9.5 mpg. The operator can view engine status online using a Cummins diagnostic system, which can send an instant email notification when a fault occurs, together with recommended action.
The Routemaster is considered the most challenging bus to repower due to a very restricted powertrain envelope, and the success of this project has encouraged Cummins to undertake similar projects for every type of bus.
The London Ultra Low Emissions Zone (ULEZ)
The ULEZ provisions will require London’s bus fleets to move to all-Euro VI compliance or face significant penalties by April 2019. The introduction of Euro VI is also expected to spread to other UK cities to meet necessary air quality improvement. Although significant numbers of new Euro VI buses are currently entering service, the rate of replacement means that fleets must continue to operate legacy buses compliant to earlier, much less stringent emission regulations.
Using either the Cummins four-cylinder B4.5 or six-cylinder B6.7 engine, the repower system is fully compliant to Phase-C level of the Euro VI standards. This mandates a useful emissions life of up to 700,000 km for the bus and requires 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.
The Cummins Euro VI engines are compatible with running on B20 biodiesel or HVO renewable diesel. Compared with conventional fossil-based diesel, HVO offers the potential to reduce greenhouse gas (GHG) emissions by 40 to 90% over the total life cycle of the fuel, depending on the feedstock of the fuel.
One of the first repower projects is nearing completion at Millbrook Special Vehicles, with a 2009-built Euro V London double-deck bus receiving a Cummins B6.7 Euro VI transplant. 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 at the Millbrook Proving Ground, with initial results demonstrating higher fuel efficiency with stop-start technology and improved drivability.
With a large number of Cummins-powered buses in operation both in London and around the country, the emerging Euro VI repower opportunity spans many different models and emissions levels. Depending on the age and condition of the bus, each project will be individually evaluated. Some may only require a simpler engine-aftertreatment replacement, while others may need a complete powertrain refurbishment and fabrication work – with various levels of upgrade in between the two extremes.
