In the previous chapter, specifications of trucks as listed in sales catalogues - such as engine torque and maximum revolutions, gear ratios, etc. - were studied in order to understand vehicle performance. However, they do not provide sufficient data for evaluating the actual truck's performances.
For instance, trucks are seldom run at their rated maximum speed. In fact, they are usually operated with engine speed at maximum torque or at the speed where fuel consumption is minimized. In climbing hills, there may be occasions when the engine revolution is raised to its maximum to produce the maximum horsepower; however the most efficient method of operation is to use the range of engine speed, which maximizes torque. If an engine's speed range, producing maximum torque, is extremely narrow, a slight increase of rpm will cause a substantial loss of power - a sign of poor performance characteristic. In other words, engines with high maximum torque and horsepower are not necessarily the most "gpowerful engine." Factors other than the maximum values of the torque and horsepower must be evaluated in determining the practical performance of engines.
Furthermore, a high performance engine must be combined with the correct transmission and differential in order to produce the desired running performance.
In addition to learning about the maximum-performance characteristics of the truck - explained in the previous chapter - it is necessary to understand the factors affecting its ease of operations. For this purpose,
you must learn to interpret engine and vehicle performance curves.
The following chapters will provide you with the know-how to comprehend the significance of these performance curves. |
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