For New Owners

Sun (Auckland), Volume I, Issue 220, 6 December 1927, Page 8

For New Owners

Engine and Petrol Thoughts by the Way The motor-car engine gets its Powei from heat. Tremendous heat is ; erated when the mixture of 'mot» spirit, vapour and air i* exploded m ttia | cylinder. The temperature i* about $2 degrees Fahrenheit. The heated gas expands w*h tee. mendous force, and the piston S 'driven down in very much the s&n3 ■way that a cannon-ball i s shot from a cannon. The connecting rod icimk the force of the explosion to the cr'ni shaft, which drives the vehicle. The success of the motor fuel de. pends on the heat there is in it and on the ease with which that heat can he utilised by motors. .No matter how much potential heat a fuel may have, it will not prove satisfactory unless it can give up its heat so easily that it can be used in the motor-car engint Motor spirit should be free from tlw jundesirable parts of crude petroleum til at can be removed by the refining process. All crude oils contain a portion of unsaturated compounds like those related to the asphalts. If these unsaturated compounds are allowed to remain in the motor spirit, their tiro, ducts of combustion form sticky cam. pounds that are likely to gum tl* valves. Carburetion is the process gf mixing motor spirit and air in ric-9% ite proportions. When the mixture jomplete and uniform, motor spiijC j which of itself will not explode. e 3 plodes violently, and power is genefs i ated. The motor spirit being right, economy depends on the the motor spirit mixture. The carburettor is an important and delicate mechanism. The quantity of motor spirit that it must meter out fut each explosion is small and must be exact. About three one-thousandths (3-1000) of a cubic inch of motor spirit is all that is required for each exploi sion in the engine of the average can. This tiny quantity must be measured put in about one-fiftieth (1-50) part of j a second, and, more important still, the motor spirit must contain components that will burn completely in the almost inconceivably short time of 1-300 part of a second. Add to this the further requirement that the mixture must ha .homogeneous and properly propotv tioned, irrespective of changes in at. mospheric conditions, load, or engine speed, and it is plain that for accuracy, pn which economy' largely depends, thi motor spirit must be refined to close Specifications to meet the requirements of carburettors. In most carburettors, motor spirit, while still liquid, is sucked through a small opening at the point where it comes into contact with the air. Sluggish fuels, having a fluidity dtf. ferent from that of effective motor spirit, should not be burned in en* gines equipped with motor spirit carburettors. The carburettors were not designed for them. Fluidity can be readily understood by filling a bottle first with water, and then with treacle, and turning the pottle upside down. The water, being more fluid, will flow out rapidly, while the sluggish treacle will flow out very slowly. A similar difference in viscosity or fluidity exists in motor fuels, but to a lesser degree. Run on a lean mixture. It will give more miles from each gallon of motor spirit, and minimise carbon troubles and the dilution of the lubricating oil. Once the carburettor is set right, leave it alone; use motor spirit that is made to a set standard- Under these conditions results should be uniformly satisfactory.