PETROL CONSUMPTION

Southland Times, Issue 21576, 14 December 1931, Page 8

PETROL CONSUMPTION

HINTS ON VAPORIZATION.

ENGLISH WRITER’S OPINION

Now that petrol bis "-one ithis article by W. Gordon Aston in the Morris Owner should be read by every motorist.

The last thing in the world that a sensible motorist will ever do is to monkey wi’h his carburetter.

But it must be admitted that the temptation to do so is very strong. In the heart of every one of us there is the instinct to try and dodge any form of direct taxation. When, therefore, the Chancellor i of the Exchequer claps an extra duty upon I so-called "petrol,”' we ncriurally revolve ' schemes whereby we can get our own back. Obviously if we can increase our mileage ' per gallon by, say, 20 per cent., we can i regard the tax as cancelled out. But the question is, can we do so? And I fear that the only possible answer is in the negative. A Good Compromise. I Of all engineering products the carburI otter is perhaps the best example of a compromise. It has to fulfil so many funcI tions, some of which are almost incompatI ible. It must give a read}- start, it must ! afford smart acceleration, it must yield the ! highest possible maximum speed, and it must be economical in the matter of mile- ; age to the gallon. I Now, a very little thought will shew that i it cannot do all those things quite perfectly. This fact the maker of the car knows very I well, and so he sends out his product with ' the carburetter adjusted to give the best I all round results. This is a matter in which Ihe is guided by long and varied experiI ence. I It is a case of one quality being at issue I with another. Supposing that you are ; chiefly interested in maximum “all-out” ; speed, you can probably attain your end by ! the use of a ven- slightly rich mixture. ; This, however, will infallibly imply that j your mileage per gallon is decreased. If, on the other hand, you are keen to I get the maximum mileage per gallon, you I must be prepared to sacrifice a certain i amount of both speed and acceleration, i But, even so, the proposition is a poor I one. Use a Normal Mixture. The only people who can afford to employ a mixture weaker than normal (normal being that mixture which the car ; manufacturer thinks best) are those who ■ live in absolutely flat country. It is a : literal fact that if ’-ou do most of your j running over give-and-take roads, a mixI ture on the weak side will prove to be anyi thing but economical. ' It will mean that the power of the en- ' gine is reduced, so that the hill-climbing ■ abilities of the car on top gear are sseri- ■ ously impaired. Tests have shown that , if you have to drop down to second, then :at a given speed (say, twenty miles an ‘ hour) .your petrol consumption will be ali most double what it is on top gear, so that any advantage that you may think you are gaining on the level is quickly stultified. As a matter of strict fact you do not gain anything- to speak of on the level, unless you are so fortunate as to use utterly deserted roads. In the ordinary course of events motoring is a long series of decelerations and accelerations. Undoubtedly that car which has a quick getaway is not only the nicest to drive, but, ' what is very much to the point, will average well without the driver having recourse to maximum speed. Aiming at Real Economy. To get real economy in a carburetter, and incidentally to get the best out of your car, the thing to aim at is, first and foremost, good acceleration, which is the same as to say the maximum top-gear scope. This may involve a very, very trilling additional amount of fuel consumption, but it is well worth while. Good acceleration is not only a factor of enjoyment, it is also a valuable factor of safety. In regard to these matters I came across a rather striking instance last year. One whom I met in the wilds of Wales, who like myself was exploring deserted and, therefore, intensely interesting by-ways, complained that his engine was always ready to boil upon the least excuse. So much so, indeed, that part of his essential impedimenta was a couple of gallons of spare water. This struck me as all wrong, for this particular make of car is not by nature a boiler. Having little else to do on a nonfishing day, I attempted to investigate the matter. I had suspected an ultra-rich mixture, but a piece of paper held near the mouth of the exhaust pipe clearly showed this assumption was incorrect. In point of truth, the very reverse was the case. The mixture, in the interests of economy, had been set so “lean” that the engine demanded a gear change on the most miserable gradient. A more reasonable adjustment of the jet was tried, whereupon the boiling trouble ceased. And a point not to be forgotten is that the consumption was not increased. Sub rosa, this my acquaintance admitted that in a moment of enthusiasm and folly he had interfered with his carburetter. I submitted this question to him: “Do you imagine that you, with your one car, know more about carburation than

people who are handling many hundreds of cars every week ” To this he could return no reply; so I rubbed it in with the remark that' the car constructor of to-day only gains success on the basis of wisdom, and the beginning of that wisdom is that he must give his customer satisfaction. In the matter of carburation he certainly does so. And that is why I recommend every car owner to trust the expert knowledge of the maker and to leave his carburetter severely alone.