SPEED OF ENGINES.

Putaruru Press, Volume IV, Issue 164, 23 December 1926, Page 7

SPEED OF ENGINES.

.WHEN SMALLER TYPES DIFFER. i ' Those "who take an interest in the relative performance of different cars arc ■ often puzzled when they find that machines with engines of an almost identical type and cubic capacity, with same sized tyres, have not got the same range of speed. One car, for example, may have a inaximum of 40 miles an hour on third, another is unable to exceed 30 or 35 on - athe same gear. Nor is there any api -parent evidence of the reason. Many things combine to limit an engine’s speed, but the principal is that the (Cylinders can fill and empty only at a relatively low speed of revolution, "taking less and less charge as that speed increases. It follows, therefore, "that if there is the slightest impediment to the entry or escape of the gases in one engine which is not present in the other, that will bo sufficient to lim.it the performance. It may be that one engine has a smaller choke tube than the other, or that both have similar choke tubes, but the internal pasages of one are either longer and more tortuous or of less area at one particular point than the • jpther. V , The exhaust gases of one car may * freely, leaving no residue, those bf the other may be baffled to make the car run silently. In both cases the engines “rev” until a point is reached where little mixture indeed is Teaching the cylinders, only sufficient, in fac\ to keep the engine revolving at that speed, but the limit speed is lower in one than it is in the other. is a subsidiary cause of trouble, as it may happen that one engine develops a rough, unpleasant period at 35, the other at 40 miles an ' hour. Consequently one engine is deemed to have reached the top of its “revs” •at 35, the other at the higher spend. In a sense vibration does not limit the speed, but the presence of something r imbalanced can really be regarded as a W - factor increasing the load on the various parts of the engine concerned.