Euro VI repowering solutions 

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Ashley Watton, Cummins’ director for on-highway business Europe, discusses the viability of Euro VI repower solutions

While electrification may be in the headlines, an alternative route to achieve cleaner air quality in our cities is gathering momentum – the repowered bus. In a bid to speed up the adoption of Euro VI clean diesels, Cummins trialled the benefits of repowering an old bus – a 1962 Routemaster RM1005 – ready to meet the 2019 London ultra-low emission zone standards (ULEZ).

The bus sports a new, clean, Euro VI diesel engine and exhaust system, which is supported with the latest Connected Diagnostic technology from Cummins.

Among other work, the Routemaster has been used on the heritage bus route between Tower Hill and Trafalgar Square in the UK capital, delighting tourists and locals alike. The venerable appearance of the bus is deceiving –  installed under the skin is the latest four-cylinder B4.5 engine built at the Cummins Darlington plant. This means it’s as clean as any of the newest diesel buses working in London today – not bad for a bus that entered service in 1962.

One of the reasons we decided to look into a repower solution is the ability to significantly extend the life of an older bus by upgrading to the latest Euro VI emissions standards without the higher costs associated with buying a new bus. Moreover, this initiative will enable bus fleets to accelerate their adoption rate of cleaner Euro VI powered-vehicles, particularly with many UK cities looking to introduce low emission zones, following London’s example.

Selecting one of the oldest buses available also demonstrated how far this technology can be stretched – if a 1962 Routemaster could be repowered to be as efficient as the newest buses on the market, then it is clearly possible to apply this technology to a vast array of buses that no longer meet current, more stringent Euro VI emissions standards.

When the project started, we had a heritage bus, owned by Sir Peter Hendy, meeting only Euro I standards with an old six-cylinder engine. By the end of the project, the bus met the requirements for Euro VI and boasted a smaller, lighter four-cylinder engine. To do this we had to completely re-engineer the entire powertrain. This was achieved by installing a new engine, upgrading to a more efficient transmission and downsizing to a Cummins B4.5 clean diesel engine. The highly compact 4.5-liter and its integrated exhaust aftertreatment made it an ideal fit for the small engine compartment and allowed our engineers to undertake the repower without altering the external appearance of the bus. We also made a few improvements inside with the driver dash panel and pedals modernized to align with the new engine technology.

The bus also comes with another technological surprise. It features Cummins Connected Diagnostics, an integrated telematics system that beams data over the airwaves to a laptop or phone making it possible to monitor the health of the engine and show where the bus is located. The system maximizes bus uptime, by alerting the operator when engine servicing may be due and proactively highlights any fault so it can be checked out at a convenient time.

This Euro VI repower program can cover many different bus models and emissions levels. Depending on the age and condition of the bus, each repower project will be individually evaluated: it could range from a simple engine aftertreatment replacement, up to a complete powertrain refurbishment and fabrication work.

With the 4.5-liter engine, ratings extend up to 210bhp, which was only attainable with our 6.7-liter engine a few years ago. More importantly, it could extend bus life by seven or eight years with lower servicing costs. It’s not ‘an engine in a box’ but a complete repowering option. Although it’s impossible to give precise pricing as every installation will be different, operators should expect the repower to be about 20% of the cost of the vehicle when new.

Cummins is engaging with a broad spectrum of bus manufacturers and repower delivery agents to ensure every opportunity for Euro VI bus repowers can be realized with a Cummins Installation Quality Assurance (IQA). The repower installation will be developed in collaboration with Cummins and pre-certified with an IQA to the same level as a new vehicle design installation.

Repowered systems like this go through the same emissions certification and compliance requirements as that of a new engine, including transient and steady state test cycles, hot and cold transient test cycles, onboard diagnostics stringency, and in-service emissions life requirements.

The Cummins repower features an integral stop/start system to eliminate fuel used during idling by automatically switching the engine off when passengers are boarding or alighting. This can 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 V conventional double-deck bus, the Euro VI fuel saving can reduce the operating cost in the range of £1,500 (US$1,955) to £2,500 (US$3,258) per year, making a significant impact to offset the cost of the repower. The lower fuel consumption also reduces the carbon footprint of the bus, with the potential to eliminate around 4-6 tones of CO₂ emissions each year from the vehicle.

Cummins Euro VI bus 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 emissions by 40 to 90% over the total lifecycle of the fuel, depending on the feedstock.

In summary, repowering has great potential to not only extend the life of an existing bus fleet, but to help improve air quality and reduce greenhouse gas emissions. It also enables the bus fleet market to benefit from fuel savings over the extended life of their vehicles.

However, more importantly, as the bus industry responds to the requirement for energy diversification it demonstrates that diesel has an important place in future power solutions alongside Cummins initiatives with hybrid, natural gas and battery electric powertrains.

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