Don't underestimate a quiet MAN

A couple of decades ago the argument was whether LPG (liquefied petroleum gas) or CNG (compressed natural gas) would be the wonder fuel of the future. Converted Dennis Darts ran on CNG in Southampton and Deputy Prime Minister and Secretary of State for the Environment, Regions, Transport & Most Other Things in the Universe, John Prescott, launched a batch of CNG-powered Volvo B10Ls in Wolverhampton. Then Transport Minister Steve Norris launched a CNG gas bus in Bristol, and DAF told everyone LPG not CNG would save the world.

The new EcoCity gas bus is undoubtedly a quiet MAN, and there is determination for it to succeed. Will it lead a new dash for gas? Stephen Morris takes it for a test drive.

But all was not well. Infrastructure costs made it a difficult technology to introduce and dubious performance, particularly when the sun came out or when it got too cold, caused this brave new technology to wither on the vine. Gas seemed to promise lower emissions, especially of particulates, about which we were all getting concerned at the time. But at the same time new European standards were coming in that would make the trusty diesel much cleaner; diesel was a technology we all knew and understood and was cheaper to run. Gas’s advantages seemed to wane on every front.

Meanwhile London started getting interested in hydrogen and at long last hybrid technology started to come good. It seemed everyone had forgotten about gas.

That was in the UK. However gas bus technology hasn’t stood still and there are gas buses in service in various parts of the world, not least in mainland Europe. Worldwide, MAN has supplied 3,000 gas buses and has now decided to introduce a right-hand-drive UK-spec gas bus. That they are not affected by extremes of temperature is evident from the fact they are in service from Norway to Portugal.

Re-engineering the complete integral LionCity for the UK would have been an expensive exercise and would probably have led to some compromises. Instead MAN is bringing in the EcoCity, which is to be sold as a complete MAN product, with full warranty from MAN, but with an Alusuisse body built for MAN on a conventional chassis by Caetano. There will be a list of options which Caetano can build into the bus, such as seat types, CCTV systems and destination equipment, to give the sort of choice that UK operators like, but the bus will be a complete product supplied by MAN and covered by a single warranty. You can even specify different front- and rear-end styling, either based on the standard Caetano product or on the LionStar.

That’s all very well, but what does a gas bus offer, and how will this be different from what went on before?

To answer the first question, it actually seems to offer quite a lot. The cost equation has changed somewhat over the last 20 years, as diesel prices have spiralled. Gas prices are no longer linked to oil prices and there is a promise of fuel cost savings in the order of 30 per cent over diesel. That’s comparable with a hybrid, but the cost premium over a diesel bus is much lower for the EcoCity, at around £50,000, than for a hybrid, for which the premium is typically twice that. Like hybrids the EcoCity qualifies for Low Carbon Emission Bus grants and attracts BSOG equivalent to 100 per cent of the fuel duty. Then emissions of CO2 are greatly reduced over those of diesel buses and particulates are almost non-existent. The EcoCity already reaches Euro6 which, reckons MAN, will add around £15,000 to the cost of a diesel bus, and there is no need for additives or particulate filters.

To answer the second question, it seems two things have changed. One is that the previous generation of gas bus engines were essentially diesel engines with the cylinder heads hollowed out to give a lower compression ratio and with a spark ignition system fitted. The EcoCity uses MAN’s E2876 LUH 04 engine, a hefty 12.8-litre horizontal unit which was conceived from day one to be a gas engine. This unit has been in production for around seven years and by all accounts has proved itself to be fairly trouble-free. Some earlier conversions at least replaced the injector with a spark plug, mixing gas and air in what was effectively a carburettor, but as well as a spark ignition system the E2876 uses a Bosch fuel injection system to inject the gas into the cylinders. The engine is described as being designed for CNG from the crankshaft up, with a hardened crankshaft and hardened valve seats.

The other thing that has changed is that MAN is working in conjunction with the Gas Bus Alliance, an organisation that embraces various technologies to ensure the supply of gas. GBA negotiates gas supply and brings together producers of bio methane, which essentially captures methane from sewage and food waste, cleans it up and feeds it into the natural gas network. By a system of credits GBA can supply only as much gas as is fed into the system from such producers, of which there is enough at present to fuel around 250 buses, though this is set to increase rapidly. The GBA believes that sufficient gas can be produced in this way to power the UK’s entire public transport system.

This leads to a claim that the gas bus is actually carbon neutral; any CO2 the bus emits would have been emitted into the atmosphere anyway had the bio products (to be euphemistic) not been processed into methane gas. In any case the well-to-wheel equation for gas is good, as very little CO2 is created in its production or distribution.

GBA supplies a modular fuelling station which takes gas from the nearest gas main, filters it, dries it, compresses it and stores it. The filling stations are of modular construction and a 10-vehicle filling station fits into a standard 20ft container for delivery to the site. No storage is needed for the gas, which is metered and charged in arrears. Bigger fleets would simply have more stations. Filling takes about five to 10 minutes on a fast-fill basis, although a smaller compressor can be supplied to allow overnight fuelling with an automatic shut-off. The fast-fill facility also gives opportunity for operators to sell fuel to third parties at a profit; Mercedes is offering CNG-powered versions of the Sprinter and VW is offering a CNG Caddy, so there may be potential for fuel sales.

The filling stations are supplied as part of a gas supply contract, which can be on a three- to five-year basis tracking the price of diesel, at a rate typically around 30 per cent cheaper in terms of pence-per-mile, or a fixed price contract of up to three years. As the fuel is paid for after it is used and is supplied from the mains there is no need for bunkering or for regular fuel deliveries. It is also very clean to use, with no danger of fuel spills. Being lighter than air, it vents to the atmosphere in the event of a leakage and ignites at around 640°C, compared with 210°C for diesel and 246°C for petrol.

Where mains gas is not available, gas can be delivered by tanker and stored in the fuel station.

One of the previous problems with gas buses was the effect of contaminated gas supplies. In fact, says Phil Lowndes, business development manager for GBA, the quality of gas supplied in the UK is very good, consistently up to the 90-94 per cent methane content the gas bus engine requires. What is less consistent is the standard of gas mains, and old leather jointing of gas pipes which had dried out was being restored by the application of a mix of water and glycol. In normal gas appliances this is little problem, but inside an engine the mixture proved the principle that liquid can’t be compressed and led to some catastrophic engine failures. This lesson has been learned and the drying and filtration aspects of the new stations ensures this won’t happen. The on-going replacement of gas mains with plastic piping is also helping in many places — despite the number of bus services that get disrupted in the process. Moreover with MAN and GBA working in partnership there is a promise that warranties will be met without arguments about whether it was bad engineering or ‘bad gas’ that led to a failure. However Phil Lowndes points out that in Porto, where 250 gas buses have been in service for up to 13 years, not a single engine failure has been experienced.

MAN can also offer a full repair and maintenance contract at £585 a month.

Two versions of the EcoCity are being offered in the UK, a full low-floor version with the horizontal engine located in the rear nearside corner and driving to a portal axle via a conventional ZF or Voith transmission; with a low-entry version, also using the horizontal engine, to follow. There are plans to introduce a midi version with a vertical six-litre engine. Two demonstrators are already at work in Britain with a third to come in April, and Tony Griffiths, UK bus general sales manager for MAN, is confident of a market for 50 next year. One has been in service with Stagecoach in Merseyside for six weeks, and another is following it with Arriva on the same patch. It was driven by 52 drivers who were apparently all very positive about the bus.

We tried out the demonstrator that had been with Stagecoach. It’s a 42-seater, including two tip-ups in the wheelchair area, though the cooling pack intrudes into the rear end leaving space for only three seats (a fourth was deemed too narrow at certification and is now a luggage space). However reshaping of the cooling pack will allow for four seats at the rear. The low-entry version will give an extra two seats and eliminate the need for rear-facing seats over the rear wheelarches.

Styling is very much what one might expect of a Germanic citybus, even given that its body is built in Portugal; simple, plain and clean cut with bonded glazing. Stylish pods on the roof contain the aluminium composite tanks that store the gas at 200bar, and give the bus a range of around 300 miles.

The interior is similarly plain and simple; with big windows and light-coloured materials it’s all very bright and has a spacious feel. With the horizontal engine under the nearside seats towards the rear there isn’t too much of a climb up to the rear seats — the step-free gangway goes almost to the back — and there is plenty of headroom there.

The cab is also plain and simple with a neat arrangement of switches and two smart dials for the speedometer and rev counter plus a digital display for the gearbox. The dials look to have come from the VW car parts bin, and the speedometer could have been positioned better for a clearer view; it was marked in km/h, though with smaller mph markings. There is also a row of four smaller dials for fuel, engine temperature and air pressure. In addition to the battery isolator switch and starter there is an ignition switch too. Gears are selected by a simple rotary switch with drive, neutral and reverse positions. Lights have a slightly dated-looking rotary switch. Other switches are neatly positioned in logical groups and the handbrake is very well placed for ease of use.

Starting the bus gives the biggest clue that this is different from a diesel; once the battery isolator and ignition have been turned on, pressing the starter is a slightly tricky art. This is because at tickover the engine is not only virtually silent from the cab, it’s also completely free of vibration, so it’s difficult to know just for how long to press the starter; you can’t easily tell whether the engine has started or not other than by watching the rev counter.

The same smoothness and quietness apply as you accelerate away. Travelling in the saloon, even right over the engine, it is smooth and quiet, with the result that the greatest noise comes from the gearbox, though as speed increases you also get a bit of ‘swish’ from the tyres. From the cab the engine is pretty well inaudible and other than feeling the power dip for gearchanges the sensation is very much like driving an electric vehicle — a trolleybus rather than a milkfloat, that is. The bus is in effect powered by a massive, 12.8litre petrol engine that delivers plenty of power swiftly, very smoothly and silently. For all its size, power is only 275bhp, though for an 18tonne gvw bus that is ample.

MAN had chosen a route from its Swindon headquarters on A roads through Royal Wootton Bassett, Lynham, Calne and Wroughton; possibly not typical terrain for what is likely to be a largely urban bus, though it proved itself a very capable interurban bus too. The top speed limiter cut in at 54mph, when the big engine was doing a lazy 1,800rpm. It seemed very well matched to the ZF six-speed automatic which gave almost seamless changes, though on this particular installation the kickdown had been disconnected and there were occasions when climbing when it stayed resolutely in sixth when fifth might have been nice to maintain progress.

With such a quiet engine it was all very relaxing, and any shortcomings of the bodywork would have shown up. However apart from wind noise around the offside mirror, there was next to no extraneous noise: Caetano’s aluminium body seemed to be well put together and free of creaks, rattles and groan, though there wasn’t a cash tray fitted which might have spoiled the peace and quiet. There’s a huge single-piece windscreen which gives excellent visibility, and the only drawback was that on a sunny November day, with low sun, there was quite a lot of reflection in the assault screen which made it difficult to see the nearside mirror at times.

The retarder seemed well set up, though pulling up to a completely smooth stop was a little tricky. Brakes were however well up to the job. For a rural run the steering was a bit on the light side, and if you cornered quickly there was a sense of the roof tanks adding to the sway slightly, though nothing alarming. Ride otherwise was comfortable and smooth and complemented the smooth quiet power delivery.

Bowling along the open road was very peaceful and relaxing, but it was in town centres that you really noticed the smoothness and quietness; stop/start work just emphasised how incredibly free of vibration the engine was and round town the light steering was much more of a benefit than out in the country. It was also easy to drive smoothly in town, with plenty of power to keep up with traffic but delivered gently and progressively.

It was easy to see why Stagecoach’s drivers had found nothing to complain about; it’s a very competent bus with adequate power delivered in a smooth, flowing way. The steering wheel is adjustable for reach and rake and it was easy to find a very comfortable driving position. All other controls were just in the right position, and doors were controlled by clearly marked illuminated buttons.

All in all it was hard to fault, and passengers would definitely be impressed by the smoothness and quietness, as I was reminded on my trip home from the station on an especially rough eight-year-old Mini Pointer Dart which rattled and banged its way along with its four-cylinder Cummins snorting away beneath my rear seat. It was like comparing chalk with cheese.

Certainly the Quiet MAN should not be underestimated. It appears the technology should provide few worries and the environmental credentials are impressive. If the package involving the fuelling station and guarantees of reduced fuel cost can be tailored well to operators’ requirements there is no reason why gas shouldn’t now have a second chance to prove itself. And while it can be produced from raw sewage in a matter of about 32 days it’s a long way from reaching peak production yet

Thanks to www.busandcoach.com for reproduction of this article

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