VARIABLE COMPRESSION

Otago Witness, Issue 3555, 2 May 1922, Page 46

VARIABLE COMPRESSION

Stories are floating around (states the Daily Mail) of doubled outputs from certain German engines, and the explanation, it would appear, is the employment of variable compression or of super-charging. Variable compression may be secured by various means, such, for instance, as incorporating an adjustable eccentric or bell crank lever in the crank throw, a method that has been tried with a certain amount of success. The advantages of variable compression are obvious. Every driver knows that if he could vary the compression of his engine to suit running conditions at any particular moment his over-all performance would be enormously improved The top gear car that one hears so much about is a car fitted with a low compression engine, but unless it be of abnormal si?.e the low compression engine can newer give anything like high speed on the level. The high efficiency engines, that share the popularity of the low efficiency type, have high compressions, and they are the engines that suit the driver who likes frequent gear-changing and to hear the tune cf an engine turning over at several thousands r.p.m. It is never suggested by the most enthusiastic advocate of either engine that the other has no special advantages, and it is obvious that if the good qualities of both types could be embodied in one engine the result would be highly desirable. The high efficiency engine is economical, the low efficiency engine is generally extravagant in fuel. The low efficiency engine is easy to drive, and the high efficiency engine requires a certain amount of skill. Thus the German variable compression engine certainly would have a very useful appeal were it not that the means by which the variable compression is obtained most probably more than discount the benefit. Many extra working parts are added to the engine, and in the hands of an inexperienced owner trouble and probably disaster would soon develop. Therefore. it would appear that these efforts are likely to prove abortive.