bhs@siemens.UUCP (07/02/85)
The previous response is theoretically correct. Unfortunatly, in practice, this does not quite hold true. There is a limit to the previously mentioned equation: the formula holds true at rpm levels below the torque peak. The way actual combustion engines work, there is a certain engine speed at which the torque output will peak. Torque is really no more than a measure of how much energy the engine can put out for each single revolution of the engine. This number is very strongly affected by a large variety of factros ranging from combustion chanber design, valve timing, to fuel used. Above a certain engine speed, the engine begins to lose it's combustion efficiency, and thus the amount of energy generated per revolution will decrease. Horsepower is really the sum of the energy output over a certain time period, a measure of how much work the engine can do. This is quite directly related to torque and engine speed, since there is a giant trade off happening now: while torque will be decreasing, the number of firings increases, so the question boils down to determining whether the net sum increases or decreases. This, too, is determined by the design of the engine. Sports cars will tend to stress horsepower at the expense of torque in order to gain acceleration, while luxury sedans (most noteably Jaguars) will tend to go for torque. This means that the engine is capable of pulling the car over a wide range of rpms. Another hidden advantage of torque: the slower an engine has to turn in order to move a car, the less internal friction it has to overcome. Thus, there is a fuel savings to having a slower engine. This is why car manufacturers will tend to have tall gears, and is why the overdrive is so common now. If an engine can be made to supply more torque, it will not have to turn as fast in order to move the car at the same speed, and thus can potentially end up increasing fuel economy. Bernard H. Schwab Siemens RTL, Princeton, NJ