THE MOST ECONOMICAL SPEED.

Star (Christchurch), Issue 16938, 12 January 1923, Page 3

THE MOST ECONOMICAL SPEED.

The figures obtained in a. series «\f tests carried out by the light car and cycle-car with the object of finding out the road speeds at which a light carused the least fuel to cover a given distance are both instructive and interesting, and demonstrate that on the particular car used the most economical touring speed was between 25 m.p.h. and 30 m.p.h. At speeds Irelow and in excess of this the consumption, it being noticeable that almost the same figures were obtainable at 40 m.p.h., 45 m.p.h., and 15 m.p.h. to 20 m.p.h , whereas one would have imagined that the consumption would have varied directly as the speed. A solution may be provided by the fact that at certain engine speeds, corresponding with a 25 m.p.h. to 30 m.p.h. road speed, the turbulence of the gases is used to the best advantage. Otherwise it is difficult to understand why the consumption should decrease when the throttle is opened up to a certain point. The fact that a saving of close on 6d a gallon can be effected by driving at the most economical speed is important, and suggests that it would be worth while for any owner who studies economy to discover for himself his car’s most economical speed. To io this he only requires a. speedometer with trip reading and a measuring glass, which may he bought for about half a crown from any chemist. He should then select a suitable testing ground, preferably level, to enable the runs to be made on top gear only, and when once the carburetter and tank are run dry commence his trials at varying speeds. Obviously, it is not possible to keep the speedometer hand constant one one mark, but if a 5 m.p.h. variation is allowed and each test is made twice some reliable data should lie obtained.