Automotive Technology Power And Torque Explained

What do power and torque figures mean? Well, the two figures are very easy to understand if you have a physics A-level, but can be rather confusing to the layman. The two figures are at the same time intrinsically linked, and yet very different. By looking at the two figures in full, it is possible to get a reasonably accurate idea of the character’ of an engine. To avoid complicating things, I shall ignore the car’s weight, and assume that all comparisons are of a car that weighs the same clearly the effects of both power and torque are increased if the weight is reduced, and decreased if weight is raised. Right, so let’s explain power first. Put simply, power is torque times revs per minute torque is literally a way of measuring force. Now acceleration equals force (torque) divided by the mass (weight, in layman’s terms), so you might well think that torque is actually the factor that determines acceleration. However, the torque figure that you have for a car is that of the engine, whereas it is the torque coming out of the gearbox that is important for acceleration. A gearbox is a method of turning less revs into more force (as in a car) or vice-versa so if we have more revs, we can convert these into more force. So to consider an example, if we have an engine making 100lb ft of torque at 5,000 rpm and one making 50lb ft at 10,000 rpm, we could fit the higher-revving engine with a gearbox with a lower gear ratio, to give the same amount of turning force at the business end of the box. A quoted power figure is actually the peak figure, that is to say the highest torque x RPM figure that the engine can produce. This means that the peak power figure essentially shows how much performance can be extracted from the engine when it is running at its full potential, and not necessarily how much performance it will have under everyday driving conditions. OK, so on to torque now. Well, first off, for the reasons explained above about gearboxes, a torque figure without an RPM figure is pretty useless. Most car engines actually produce pitiful amounts of torque 200lb ft sounds pretty impressive in car terms, but many people can actually manage that on a weight machine lifting 200lbs over a foot isn’t really that hard when you think about it, it’s about the same as a chin-up. The important point about a car engine, however, is that is can do this tens or hundreds of times a second. We can use torque figures in isolation reasonably accurately to describe car engines, as we assume that all internal combustion engines are reasonably comparable almost all produce peak torque at a 4 figure RPM. The easiest way to use torque to judge a car’s character is to compare the torque figure in lb ft with the power figure in BHP if the torque figure is higher, then you have a lazy’ engine; lots of low down grunt, but not much to be gained by revving it very high. If the opposite is true, and the power figure is much higher than the torque, then it’s a fair bet that you’ll have to rev the engine to make rapid progress. If both are about the same, then you have a reasonably unstressed engine, with a reasonable amount of low down torque, but with the highest reaches of the performance scale only available at higher revs. You can also get a reasonable idea of which characteristic your engine is closest to by looking at the peak torque figure’s RPM below 3,000 is a lazy’ engine, 3,000 to 5,000 is a normal’ engine, and 5,000 plus is a revvy’ engine. Category:Home › Autos • Will the trend toward economy-size car models lead Americans back to buying smaller-sized cars? — part 2 • You should never use after-market auto parts when maintaining or fixing your car • Should a new car be rust-proofed? • Will the trend toward economy-size car models lead Americans back to buying smaller-sized cars? — part 1 • Five safest cars in North America • How to ensure your teen drives safely after getting a license • Pros and cons of using an hydrogen generator for your car • DIY automotive maintenance: How to change the oil