Torque diagram (engine)
To avoid any misunderstandings: The above performance and torque curves have been very much smoothed out, they can on no account, be determined on a performance test bench. This form, the same scale and the very differing engines were selected to make the meaning of the torque curve understandable for everyday contact with an engine. By the way, an even higher RPM level, and an even greater difference would have been possible with a diagram of an in line, four cylinder motorcycle engine.
Admittedly, these here are two very different engines which are being compared with each other. The diagram of the motorcycle engine (on the left ) is from a Ducati 999 with 1000 ccm³ capacity and two cylinders. The shown Diesel engine is a very modern, direct fuel injection with twice as much cubic capacity and turbo-charging. The only point that is important, is that both have a performance of a slightly more than 100 kW.
Actually, this should already be obvious from the respective performance curves. The one shows a shallow climb, leading directly to the maximum, the other, a balooning curve with relatively high values in the lower speed range as well. It becomes even more clear with the torque curves. Although one can calculate them directly from the performance curves, they distinctly strengthen the information value of the performance curves. The traction force of the diesel engine reaches enormously high values very early, whereby the torque of the motorcycle engine only develops slowly. Although both engines have the same performance at their disposal, the left torque curve reaches, at best, only half the values of the right curve.If the left engine had to carry the same high load as the right engine, tolerably presentable values could only be achieved through high RPMs and a great deal of gear changing. The left engine however, suits the relatively low weight of a motorcycle better than the right engine, and due to its RPM-band being twice as wide, makes it possible, in spite of a small and lightweight engine, to drive moderately in high gear, as well as performance orientated. 05/10