FUEL ECONOMY

Wairarapa Times-Age, 15 December 1939, Page 21 (Supplement)

FUEL ECONOMY

SOME PRACTICAL HINTS. MEANS OF OFFSETTING HIGH PRICES. The recent increases in the price of petrol, have turned the minds of many motorists towards ways and means of gaining more miles from each gallon of petrol. There are two important factors, an Australian writer observes, which affect the rate of petrol consumption — the manner in which the car is driven and the car's mechanical condition. With regard to this latter point, it is not satisfactory to experiment with smaller jet sizes or proprietary brands of so-called petrol economisers. It is best to retain the factory specifications in every respect, but to keep the car in really first-rate tune, and drive it steadily. The effect of speed and violent acceleration on fuel consumption has been tested very thoroughly in recent years. A year or two ago. a 25-h.p. car, weighing about 29cwt. gave 25 miles a gallon at 30 miles per hour, but as the speed was increased, the rate of consumption increased, until at 70 miles per hour it was 10 miles per gallon. When a car is accelerated violently by pushing the throttle hard down to the floor, consumption is much heavier than when the gentler methods of picking up speed are employed. All modern cars have incorporated in the carburettor a special accelerating pump, which only works on movement of the throttle. Its purpose is to temporarily enrich the mixture, to give more power when the car is accelerating. and it does this by squirting liquid fuel into the carburettor barrel. The

amount going in depends on the amount of throttle opening. With full throttle, it is considerable. MECHANICAL CONDITION. From the foregoing, it will be appreciated that a great deal is to be gained simply by careful driving. But if the owner also is careful to keep the car in good condition mechanically, even better results may be achieved. In engine tuning, the valves must always be the starting point. Some motorists actually boast that they drive their cars for 50 and 60 thousand miles without grinding the valves or cleaning cut the carbon, claiming that their engines do not need it. There is no more unwise practice. Engine performance drops, gradually as the formation of carbon becomes heavier. As performance drops, consumption increases, because wider throttle openings are needed on hills. As a general rule, a complete top overhaul every 10,000 miles is wise. Cars vary somewhat in their requirements in this respect, but if that rule is followed, the owner will not be spending money extravagantly.

The next requirement is to keep the ignition system and the carburettor in good order. These need to be looked over every four or five thousand miles. The plugs should be removed. cleaned, and their gaps reset to the distance recommended in the car’s instruction book, and the tungsten points of the make and break examined and cleaned with a fine magneto file, if they appear to be black. WATER AND DIRT. With the carburettor, all that is necessary is to keep it free of water and dirt. The float bowl should be drained and wiped out. At the same time, the glass bowl of the petrol pump should be removed, emptied and cleaned. Finally, do not overlook the fact that petrol consumption will increase if undue friction in the running gear prevents the car from rolling freely. Such friction usually is caused by binding brakes, which need to be adjusted very carefully if friction is to be avoided.

The only points of adjustment in the carburettor to be checked are those controlling the idling mixture and the throttle opening for idling speed. The mixture should be made as lean as possible. without causing uneven running, and the idling speed should be set at the lowest point at which the engine will run without, stalling.