CAR POWER UNITS

Southland Times, Issue 22915, 13 June 1936, Page 19

CAR POWER UNITS

CORRECT MIXTURE IMPORTANT Consistent and successful efforts have been made to improve the power output of motor car engines during the past few years, states an English motoring journal. During this phase of development the virtue of economy in fuel consumption has become sadly neglected, with results that are wider in scope than is generally realized. The direct loss in miles a gallon is only one of many disadvantages, and is not so serious as are the mechanical troubles which occur in an engine that uses over-much fuel. The way in which the modem power unit is so often designed and driven frequently results in the forcible feeding of the unfortunate cylinders with indigestible mixtures of petrol and air; over-richness and imperfect atomization are faults which make it impossible to secure clean and rapid combustion. To'these causes are often traceable troubles such as cylinder wear, burnt valves and the erratic performance of sparking plugs. Like a good chef, the carburetter may prepare a perfect meal, but has no control over the journey which that meal must make from the throttle to the cylinders. It is on this journey that the character of the mixture is apt to deteriorate, especially under modern traffic conditions, when the throttle is suddenly opened and Closed many times a mile. The most popular palliative at the present time is the exhaust-heated “hot-spot,” which, in big engines, reaches the dimensions of a stove in which the “meal” is cooked so thoroughly as to become a vapour. This practice safeguards the engine, but cannot be applied to small power units owing to the loss in output which it inevitably involves. It seems quite possible that the supercharger, primarily developed as a means for increasing output, may come into its own by reason of the mechanical mastication of the mixture provided by the whirling vanes. It is a general experience that supercharged cars get away very easily from cold, with but little use of the strangler, although their design is usually such that no form of “hot-spot” can be applied. This feature has undoubtedly an important bearing upon the low rate of cylinder wear which has been noticed in a number of touring cars running with a moderate degree of “boost.”