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Now's the time to study LPG

28th May 1976, Page 21
28th May 1976
Page 21
Page 21, 28th May 1976 — Now's the time to study LPG
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Which of the following most accurately describes the problem?

by the technical editor RISING FUEL costs have prompted many operators to look at LPG (liquefied petroleum gas) as an alternative fuel to dery or petrol because it is cheaper, and LPG, it is claimed, causes less exhaust pollution.

To discover the up-to-the-minute situation I visited Autogas '76, organised by Yorkshire Autogas Ltd at Shay Syke in Halifax. Many operators and manufacturers interested in LPG were brought together and a wide range of vehicles from a doubledecker Daimler to a Ford Escort van were on show.

One, the Cleveland doubledecker fitted with a straighteight B81 Rolls-Royce engine, has now completed three years in service for a mileage around 70,000. The average fuel consumption is working out at about 80 lit/100km (3.5mpg) compared with the 43 lit/ 100km (6.5mpg) for the equivalent diesel version.

The internal noise level has been lowered by around 7dBA owing to the change of power unit although the external noise has not altered, principally because of the fan.

One of the main advantages claimed for LPG is its low level of emissions making it ideal for city operation. Rolls-Royce claims that the B81 gas engine (which has been developed as a complete unit rather than by a " bolt-on conversion ") gives the most benefit on stop/start operation. But the company does not recommend it for trunking work.

A number of light vans on view had been converted to running on gas. A Ford Transit with a V4 petrol engine had had the treatment which Mr Don Westerside, joint managing director of Yorkshire Autogas Ltd, claimed could be carried out by one fitter in about eight hours. The LPG tank in this instance was fitted behind the driver's seat taking up a certain amount of load space.

If the load space requirement is critical for the operator the tank can be mounted on the roof as demonstrated on an Escort van. For the Transit the tank contained 77 litres (17 gallons) of usable fuel which is 80 per cent capacity of the tank—a space is left to allow for expansion.

In practice, operators are finding that there is a 10 per cent drop in mpg, but this is balanced out by the cheaper retail price of the fuel. In fact, some operators are finding that there is no difference at all in the fuel consumption. However, it is thought that the cause of this is running too rich as a petrol unit ; and on several occasions it was discovered that the petrol was being " nicked " for private use !

Motorway work

Owing to the absence of lead in the fuel, exhaust valve seat recession has occurred in some engines which have been involved in high-speed motorway work. This has not been a problem on urban work and hardened valve seats effect a permanent cure. To see—or rather hear—for myself just what the improvement in noise level was like with an LPG engine I tried a Commer Commando G 1295 fitted with the Chrysler V8 petrol-engine option. It was unladen so I could not get any impression of torque characteristics, but I was certainly impressed with the lack of in-cab noise.

One problem with having a very quiet engine is that you can hear other noises which are normally mashed, such as suspension creaks and groans. The fan noise on the Chrysler engine was very pronounced— a great pity as at 30mph there was no trace of engine noise.

In 1974, Yorkshire Autogas developed a spark ignition version of the Perkins 6.354 diesel engine to run on LPG. The combustion chamber and compression ratio were designed specifically for the fuel and the resultant power output is the same as the diesel version but has improved torque in the lower-speed range. The company claims that the installed noise level is reduced by approximately 10dBA in most vehicles.

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Locations: Halifax, Cleveland

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