Image for representation. The terms horsepower and torque are probably tossed around the most when talking cars. While your folks might tell you that one or the other is the only number that matters, the case might be a bit more complicated than that.
Building a car ground up is not just about cramming a big block under the hood and expecting the best before it can be called a proper car, the engine needs to be tuned in accordance with the kind of car you want it to be — performance or fuel-efficiency. As on the video below, Jason Fenske from Engineering Explained illustrates the meaning of both terms and how it matters. Such that when you check the specification of the bike, then the engine would have a particular torque figure at a specific RPM.
Such that delivering a more significant number of torque at a higher RPM proves to be powerful and the torque deliverability will be higher as well. BHP, on the other hand, is the rate at which the torque generated by the engine in a bike is delivered to the wheels.
Such that faster the deliverability, higher is the speed of the motorcycle and vice versa. For a bike that consists of a lower BHP can pull higher loads and for a bike that contains a greater BHP can propel the bike at faster speeds.
Thus, BHP depends on several factors such as deliverability, weight and power generation of the bike. Imagine if two bikes have the following specifications. Thus, when you look at the above-given specifications of two bikes, then for top speed the second one would propel the bike with more excellent acceleration and more significant-top speed. In comparison to the first one, that would have a lower top speed along with a slow acceleration point as well.
But with twice the turning force produced, you can expect the bike to pull heavier loads and still maintain its power and deliverability throughout. A fairly typical small family car engine puts out, say, 60bhp brake horse power at rpm. The same engine can be tuned or modified so that it gives 80bhp at rpm. But although the power is greater, the peak torque can actually be less, as well as occurring at a higher engine speed. There will be less torque at low and medium engine speeds.
In other words, though a car with the tuned engine would have a higher maximum speed, it would only accelerate better as long as the gearbox was used to the full to keep the engine speed up, assuming the gearing remained the same. In practice, the highly tuned car would almost certainly need to be differently geared to remain drivable - the gears would have to be more closely spaced and the overall ratio slightly lower. The usual engine test procedure is to run the unit on a 'brake' or dynamometer which measures torque over a large range of speeds by seeing how much braking effort is needed to keep the engine at a steady speed on full throttle.
The torque times the engine speed then gives the power output, called brake horse power bhp. Power measured like this, with the engine on a test bed, is expressed as a power output at the flywheel. This is less than the power at the flywheel because of frictional losses in the car's transmission system, but it gives a more realistic idea of how the car will perform as it shows how much power reaches the road. To further complicate matters, European and Japanese car manufacturers use a metric measurement of horsepower.
One metric horsepower is slightly more than one brake-horsepower. Why the difference? Well, on the part of the car magazines, old habits die hard. There was a time when the kilowatt was the preferred measure. The higher the number of kilowatts the more powerful the batteries.
You might be wondering where torque comes into all this. In simple terms, torque is a different measurement of the work an engine can do, taken from a different part of the engine. The ideal is an engine with lots of both.
Think of the difference between power and torque as the difference between an explosion and a fire.
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