How To Drive A Motorcar
A Key To The Subtleties Of Motoring

CHAPTER IX Throttle and Ignition Control MOST carburetters in these days are of what is termed the automatic type, and the question of the control of the amount of air used is not of such great importance as it was a few years ago. Frequently, however, one has a means of controlling the amount of air, or on the other hand one may wish to experiment with different-sized jets or needles. In either circumstance it is preferable to err on the too much air principle than it is on the too much petrol basis, as the former is not so likely to do any damage, whereas the latter may cause trouble; in fact, probably will. Naturally, the more air that can be used with reason- ably good results, the more miles per gallon will one attain, although it must be remembered that, if one is adjusting a mixture for the question of mileage, acceleration and power on the hills must not be ex- pected to such an extent as if the mileage is not tc be of primary importance. Bear in mind also that the quantity of air which can be used with a given petrol flow varies according to climatic conditions, and on a warm summer day a considerably greater quantity of air can be used with a given sized jet than, for instance, on a cold winter’s day, or when the air is humid. Too much air will, of course, make itself known by popping in the carburetter, and can also be judged by the length of time which it takes the engine properly to warm up to its work in the morning. This popping, however, is not likely to do any damage to the. engine, although, if frequent, it is certainly not conducive to economical running. 75