FOR NEW OWNERS.

Putaruru Press, 19 January 1928, Page 7

FOR NEW OWNERS.

ENGINE AND PETROL. Thoughts By the Way. The motor car engine gets its power from heat. Tremendous heat is generated when the mixture of motor spirit, vapour and air is exploded in the cylinder. The temperature is about 3000 degrees Fahrenheit. The heated gas expands with tremendous force, and the piston is driven down in very much the same way that a cannon-ball is shot from a cannon. The connecting rod joins the force of the explosion to the crank-shaft, which drives the vehicle. The success of the motor fuel depends on the heat there is in it, and on the ease with which that heat can be utilised by motors. No matter how much potential heat a fuel may have, it will not prove satisfactory unless it can be used in the motorcar engine.

Motor spirits should be free from the undesirable parts of crude petroleum that can be removed by the refining process. All crude oil contains a portion of unsaturated compounds like those related to the asphalts. If these unsaturated compounds are allowed to remain in the motor spirit their products of combustion form sticky compounds that are likely to gum the valves.

Carburetion is the process of mixing motor spirit and air in definite proportions. When the mixture is complete and uniform, motor spirit, which of itself will not explode, explodes violently, and power is generated. The motor spirit being right, economy depends on the proportions of the motor spirit mixture.

The carburettor is an important and delicate mechanism. The quantity of motor spirit that it must meter out for each explosion is small and must be exact. About three onethousandths (3-1000) of a cubic inch of motor spirit is all that is required for each explosion in the engine of the average car. This tiny quantity must be measured out in about onefiftieth (1-50) part of a second, and, more important still, the motor spirit must contain components that will burn completely in the almost inconceivably short time of 1-3000 part of a second. Add to this the further requirement that the mixture must be homogeneous and properly proportioned, irrespective of changes in atmospheric conditions, load, or engine speed, and it is plain that for accuracy, on which economy largely depends, the 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 in contact with the air. Sluggish fuels, having a fluidity different from that of effective motor spirit, should not be burned in engines 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 bottle 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.