Careful tuning key to best use of L.P.G.

Press, 30 August 1984, Page 24

Careful tuning key to best use of L.P.G.

With the price of petrol now 87.5 c a litre, or about $3.98 a gallon, motorists are becoming increasingly interested in alternative fuels. In the South Island, motorists do not have much choice.

North Islanders can use petrol, C.N.G. (compressed natural gas) or L.P.G. (liquefied petroleum gas); but in the South Island the choice is restricted to petrol or L.P.G.

According to Mr Roger Lusby, the principal of a Christchurch specialist en-gine-tuning firm, L.P.G. is a better proposition than C.N.G. and, in some cases, better than petrol. Mr Lusby is a staunch proponent of L.P.G. although he admits that if all cars ran on it he would probably not have nearly the amount of tuning work that his company has at present. Provided the gas unit is installed correctly in a car with a normally aspirated engine that is in good condition, L.P.G. is as good as, if not better than, petrol. However, L.P.G. should not be used in turbocharged cars or those fitted with fuelinjection systems at this stage, he says. As part of their L.P.G. installation packages, some Christchurch firms include a tune-up conducted by Mr Lusby’s company, Vantage Motor Tuning, Ltd. Because the profit margins in L.P.G. installations are small, often his firm cannot devote as much time to tune a car to operate efficiently on both L.P.G. and petrol as is desirable, according to Mr Lusby. Moreover, in some cases, the procedure is complicated by the fact that the engine to be tuned is presented for the installation and the tune-up in extremely poor condition.

Mr Lusby suggests that anyone who intends to have

a car converted to run on L.P.G. would be well advised to ensure that the engine has been tuned to operate efficiently on petrol in the first instance.

“The installer’s job is simply to fit the conversion unit and ensure that the car will run safely on gas. The condition of the engine must be the owner’s responsibility. The responsibility of specialised tuning establishments, such as mine, is to tune the engine to operate efficiently on L.P.G. and petrol. If the engine is not in tip-top condition in the first place, it cannot be tuned to the highest standards of efficiency and, in all probability, the owner will find it giving all sorts of trouble before it is much older,” says Mr Lusby. New Zealand is a traditional do-it-yourselfer’s domain, but there is no place for Kiwis of that genre in the world of L.P.G. In fact, there is a law that bans unqualified people from tampering with the L.P.G. plumbing fitted to any car. Garage mechanics have to undergo a course in L.P.G. installation procedures and maintenance work before they can lay hands on anything connected with an L.P.G. installation on a car.

The point is that the L.P.G. systems have seals in them that must be always leakproof and if these seals are broken they can be restored to their original condition only by applying specialised techniques. “Some do-it-yourselfers who have tinkered with the installations on their cars and then struck trouble have brought them to us to rectify the problems,” says Mr Lusby. “In some cases, what they have done would make your hair stand on end. Sometimes you can even smell them coming. We get a whiff of their gas

BEHIND the WHEEL with

Peter Greenstede

as soon as they turn into our street People switch to L.P.G. with the idea of saving money. Bearing in mind that the cost of conversion could amount to $l6OO or more, quite a time is going to elapse before the motorist is actually going to save money and that time will lengthen according to the severity of any leaks in the plumbing. In fact, a motorist could possibly end up with an L.P.G. installation so faulty that it is more costly to use than petrol. The ever-rising cost of cars and accompanying operating costs have led to down-sizing to the extent that the 1200 to 1600 cu cm engine class is now the most popular among new car buyers. Many motorists believe that smaller cars do not operate as efficiently as larger ones on L.P.G. but, according to Mr Lusby, that is not so.

“In actual fact, a lot of ! the smaller engines run on gas more satisfactorily than they do on petrol,” he says. “I don’t think that the size

of the engine has any bearing on the operation.” Smaller engines are easier to run on gas, because with the dual fuel situation the mixer is of critical importance. Mr Lusby reckons there is a long way to go with carburetion in relation to gas. The mixer is on top of the carburettor and it creates the low pressure to draw the gas out of the regulator. Because the mixer is, of necessity, slightly smaller in diameter than the top of the carburettor, when the engine is switched over to petrol from gas it creates a restriction. That reduces the air flow and the engine runs rich on petrol. The bigger the engine, the bigger the restriction effect. “In some instances we have encountered serious problems in trying to get the mixture right to get the engine to run on both fuels,” says Mr Lusby. There is a legal commitment on agents who install gas conversion units to make them run satisfactorily on gas. They are not legally bound to make them run satisfactorily on both fuels. The objective is to make the car run on gas, not petrol, and that, according to Mr Lusby, is as it should be, for the object of the exercise is to make gas, not petrol, the primary fuel. “Petrol is a standby, if you are going to save money,” he says. However, there is the odd car that will not go as well as it should on gas, no matter what is done to it by the engine tuners. Actually, there objective is to obtain the maximum power setting on the leanest reasonable reading they can obtain. However, another problem that has been encountered is the air dam effect created at the front of a car as it travels along the road. When the tuning procedure is carried out on a

dynamometer, on which the car is stationary, there is no air dam effect.

Thus, on the road, a car tuned to perfection on a dynamometer may run in fits and starts simply because the air dam effect will radically change the fuel-air mixture. In the South Island, people who profess to know something about fuel will tell you that L.P.G. is the best. The fact that it retails for 45 cents a litre is a good reason for converting a car to run on gas. Anyone who puts $l6OO into a gas conversion unit must expect to achieve at least a 30 per cent saving in dollar terms, if the venture is to be worth the expense. In the South Island, therefore, the aim is to achieve real fuel efficiency, whereas in the North Island, where C.N.G. is relatively cheaper, efficiency in that regard is not so important, assuming the car runs as it should. “South Islanders expect a million miles per gallon, whereas in the North Island they don’t seem to care, so long as the car runs well,” says Mr Lusby. “It’s not really so difficult with C.N.G. to tune for economy. With a petroldriven car, performance is affected if too much petrol is fed into the engine. In fact, the car loses power. “With gas, the situation is entirely different. If twice as much gas than is needed is fed into the engine, that engine will still perform in exactly the same way as if it was getting exactly the right amount,” Mr Lusby says. L.P.G. is just as safe as petrol, he says. The important thing about it is the manner in which it is used. Another thing: although L.P.G. may work best in small engines, small cars do not have much room for gas bottles.