Fuel Quality and Its Effect on Engine Design
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CEW can foretell with any reasonable degree of accuracy the major and minor effects of such a widespread war as that in which we are involved. Consider one aspect alone, that is, the possibilities lying in the direction of the employment of high-octane fuel. The huge growth in the air fleets of the United Nations has necessitated the production of 100-octane petrol to an extent which, previous to the war, would have been almost inconceivable. In the United States alone the annual production rate at the end of this year will be practically equivalent to the total consumption of liquid fuel in Britain in 1938. Yet only seven years ago fuel of such high value would have cost about £5 per gallon ; now it is about 2s. 6d.
Some authorities in the States are inclined to • believe that even for motor vehicles there will not be any considerable return to fuels of a much lower octane value. What does this imply? The answer is far more power from an engine of any particular volumetric rating, or the same power output from an engine of much smaller dimensions than those employed for the same b.h.p. to-day. The ratio is roughly 5 to 8; in other words, the same size of engine as now develops 40 b.h.p. could be replaced by one which, in present circumstances, would give 25 b.h.p. but with the better fuel would give the same power as the larger unit.
It must not be thought, however, that any ordinary engine can be taken and used with the high-octane fuel. Necessarily, higher bearing pressures and greater general stressing would occur. Some units might be capable of withstanding such increases, but others would have to be redesigned. The vista does, all the same, present unbounded possibilities, more, perhaps, at least at first, in the private-car field, but no doubt later in that of the commercial vehicle.