Latest Mercedes City and Touring Busses: More Efficient and Lower Emissions

Euro VI rated Citaro (city bus) and Setra (Tour bus) achieved lower consumption in nose to tail runs against predecessors of 8.5 and 8.2 percent respectively.

[fimg=left]http://www.cleanmpg.com/photos/data/501/MB_Citaro_City_Bus.jpg[/fimg]Wayne Gerdes - CleanMPG - Oct. 29, 2012

Brand new Euro VI complaint MB Citaro (Micro Hybrid of sorts) City Bus – 6 mpg on an actual City Bus Route!

Setra Highway Motor Coach

In a very well designed head to head with their current best, Mercedes proved their latest Euro VI complaint, DEF via way of an SCR based city and highway touring buses are fuel savers while meeting far more stringent emission targets.

The City and Highway Buses

The new Euro VI-certified Mercedes-Benz Citaro city passenger bus and the new Setra ComfortClass 500 touring coach along with three of the previously most fuel efficient buses in their respective categories were driven a total distance of 11,160 miles while geared and loaded identically with transmissions, finals and tires being exactly the same.

The Mercedes-Benz Citaro (city buses) came in three versions: The newest Euro VI-certified model with a 7.7L 299 HP Mercedes-Benz OM 936 h engine faced the previous generation Mercedes-Benz Citaro Euro V-certified 6.4L 286 HP and 299 HP predecessors. Transmissions, final drive ratios and tires were identical in each case.

In the touring coach comparison the brand new Euro VI-certified Setra ComfortClass S 515 HD competed against its Euro V-certified Setra S 415 GT-HD ComfortClass 400 predecessor with identical engine power output. The two-axle high-deck touring coaches each measure almost 40 ft. in length. The touring coaches were equipped with the Mercedes GO 250-8 PowerShift (ComfortClass 500) and the Mercedes GO 240-8 PowerShift (ComfortClass 400) transmissions respectively. Their gear ratios, final drives and tires were identical for both high-deck motor coaches.

All buses had been broken in at the start of the Record Run with around 6,000 miles placed on the respective odometers and tire wear (tread depth) was identical before the head to head drives began.

The Setup

The five buses were driven around-the-clock while loaded at 50 percent of the payload with a realistic 7,000 pounds of ballast in the city buses and 40,000 pounds for the highway coaches.

The start and finish for the three Mercedes-Benz Citaros (city) was Wiesbaden, the capital of the German state of Hesse. With the exception of refueling stops each day, the buses operated around the clock for five days straight on route 17 in Wiesbaden. It traverses the city centre of Hesse’s capital including the pedestrian zone and outlying areas.

An Actual City Bus Route! To ensure realistic operating conditions, the test buses followed the urban buses in regular service at a significant distance. They also maintained a significant distance between each other. The elevation change along Route 17, which is 11.5 miles long, is over 1,300 ft. The buses completed 17 round trips each day and stopped at each bus stop where the buses were lowered using the kneeling function and the passenger doors were opened.

The touring coaches also used Wiesbaden as the starting point and were first driven to Leipzig. From there they made a 5,506 mile daytime loop from Leipzig via Erfurt, Schweinfurt, Bayreuth and Dresden to Bautzen and back. At night the two Setras drove a 572 mile route from Leipzig via Potsdam to Hamburg and back.

The touring coaches travelled a distance of just over 1,116 miles a day. Some 90 percent of the distance was driven on Interstates (Motorways there), the remaining ten percent on main and country roads. The vehicles travelled at the legal speed limit of 62 mph or 49 mph whenever traffic permitting.

The Results

City Bus -- With a fuel consumption of 6.1 mpgUS the new Euro VI-certified Citaro turned in an excellent performance besting its predecessors with an 8.5 percent reduction in fuel consumption.

Assuming an annual mileage of 37,000 miles, the new bus pays for its up charge in as little as 4-years at $1.60/L.

Tour Bus -- The results for the new Setra ComfortClass 500 was similar. Here the Euro VI-certified ComfortClass 500 was up against the in-house Euro V based ComfortClass 400 predecessor with identical transmission gearing, final drive ratios, tires, and loads.

Travelling a distance of 4,340 miles with an average fuel consumption of 11.2 mpgUS, the new ComfortClass 500 outperformed its predecessor by using 8.2 percent less fuel on the identical route.

Assuming an annual mileage of 62,000 miles, the new Setra ComfortClass 500 saves its operator about $3,750 USD in fuel costs annually.

More on the Tech Front

In addition to the more fuel efficient drive system, ancillary components were also redesigned. Alternators, battery management, radiator fan and air compressor – these and other components play a major role in fuel consumption and in both city and highway bus model series were optimized down to the last detail.

City Citaro Euro VI: ancillary components - Two distinctive features on the Euro VI-certified Citaro deserve special mention. A lowered entrance height reduces the amount of air needed for kneeling and consequently the amount of energy required. The second point concerns the energy management: free (without diesel injection) electricity generated in overrun mode is stored in dual-layer capacitors (supercaps) and is available the next time for acceleration. This relieves the burden on the alternators and consequently reduces fuel consumption. It’s a micro hybrid!

Highway Setra ComfortClass 500: Improved aerodynamic properties are essential for the Setra ComfortClass 500 touring coach. From the rounded front with clipless blade wipers and optimized exterior mirrors to smooth flanks and the tapered rear with its separation edge, the aerodynamic efficiency of the ComfortClass 500 sets new touring coach benchmarks. The result is an outstanding drag coefficient of just 0.33. The drag is also reduced by another feature in that the bus lowers itself at speeds above 59 mph by .8 in.

The Setra on the highway making its way to your next destination.​

With fuel costs for transportation becoming the largest expense for most commercial setups, it’s the fuel economy that can and will make or break an operator. Mercedes along with just about anybody building commercial vehicles including Busses to trains are thinking outside the box and bringing their entire toolboxes to bare to bring the costs in line all the while reducing emissions to meet the latest regulatory requirements. And all appear to be doing it with minimal upcharges so far.

And is that not the right thing to do? Good for Mercedes-Benz Commercial. Now we only need to see this same level of attention spent on their US consumer based offerings.