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Power Torque Thrust - Analysis
by IKE - 23-10-2005


The purpose of this article is to clarify what torque and power actually represent and to give a general view of the manner the performance of a car or motorbike could be evaluated. The main conclusion is that the total performance of the car cannot be described by two single numbers (those of maximum power/thrust) or even worse from only one of those. These values are useful if we compare relatively similar engines and can give a vague indication but to evaluate the whole performance of a vehicle we need at least the thrust curves.


For these articles we made some assumptions which while they are not important for its purpose should be mentioned:

- We assumed that the performance of an engine is solely a function of its angular velocity. In reality many factors (load, throttle position, temperature etc) play an important role and an engine will not yield the same power at a certain rpm when circumstances vary.

- The reference route as mentioned above has a strictly auxiliary role, as a tool for comparing various cases and comprehending the effect of thrust curves in practice. If we want to evaluate it in a realistic manner we should use a repetitive process where the thrust reserve changes the velocity and also take into account vehicle dynamics (traction, inertia etc). This simulation is already been done in industrial or research level but for the purposes of this introductory article it highly complicates things. Motorsports is a field where these simulations are also very useful in order to optimize the performance of the vehicle and select if possible the optimum gearing.

- There are also some other factors we haven't taken into account in order to simplify our approach. The engine response and the internal inertia of the engine (its ability to change its angular velocity fast) are some of them and while important they were not included to our approach for simplicity.

(article update 20-3-2010 - IKE)

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