Relationship between speed and horsepower

All about Horsepower, Torque, speed, and acceleration.

relationship between speed and horsepower

What's the difference between torque and horsepower? In a vehicle, torque is measured at various engine speeds, or revolutions per minute (RPM). Mathematically, there's a relationship between horsepower, torque, and engine speed. Engines that make massive amounts of torque at low. So what really is the difference between torque and power? Simply put, torque is a rotational force coming from the engine & transmission to drive the wheels.

The Physics of Acceleration So now for the most important thing on the page. The formula for acceleration is seen below.

All about Horsepower, Torque, speed, and acceleration.

So we are solving for acceleration and we have a constant mass. But remember, the transmission ultimately gives the force to the wheels, not the engine. The torque at the wheels is the torque at the engine combined with the torque magnification given by the transmission through gearing.

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  • What's the difference between torque and horsepower?

And RPMs are what allow us to use gearing effectively, which gives us more torque at the wheels. Notes For any comments, corrections, flames, or other types of input, feel free to contact me.

Gearing is extremely important because it controls RPMs and therefore horsepower. Gears magnify torque — hence the acceleration available in first gear. Low torque, high horsepower.

relationship between speed and horsepower

Another excellent explanation of the topics at allpar. But it runs out quickly. Racecars have high horsepower due to high RPMs, not due to high torque see gearing.

At RPMs the horsepower and torque will be exactly the same. Specializing in IoT and Application Security, he has 20 years of experience helping companies from early-stage startups to the Global Daniel currently works at a leading tech company in the Bay Area and can be found writing about the intersection between security, technology, and humanity.

Figure 1 Referring to Figure 1, assume that the handle is attached to the crank-arm so that it is parallel to the supported shaft and is located at a radius of 12" from the center of the shaft. In this example, consider the shaft to be fixed to the wall.

The Relationship Between Horsepower, Torque, and Acceleration

Let the arrow represent a lb. Because the shaft is fixed to the wall, the shaft does not turn, but there is a torque of pound-feet pounds times 1 foot applied to the shaft.

relationship between speed and horsepower

In the same way that one ton is a large amount of weight by definition, poundsone horsepower is a large amount of power. The definition of one horsepower is 33, foot-pounds per minute. Consider the following change to the handle-and-crank-arm sketch above. The handle is still 12" from the center of the shaft, but now, instead of being fixed to the wall, the shaft now goes through the wall, supported by frictionless bearings, and is attached to a generator behind the wall. Suppose, as illustrated in Figure 2, that a constant force of lbs.

In other words, the "arrow" rotates with the handle and remains in the same position relative to the crank and handle, as shown in the sequence below.

Motor production: Speed, Torque and Horsepower

That is called a "tangential force". Figure 2 If that constant lb. The output shaft of the gearbox of the engine in Example 4 above turns at RPM. The point to be taken from those numbers is that a given amount of horsepower can be made from an infinite number of combinations of torque and RPM. Think of it another way: In fact, in cars of equal weight, the smaller engine will probably race BETTER because it's much lighter, therefore puts less weight on the front end.

AND, in reality, the car with the lighter 2-liter engine will likely weigh less than the big V8-powered car, so will be a better race car for several reasons.

Measuring Power A dynamometer determines the POWER an engine produces by applying a load to the engine output shaft by means of a water brake, a generator, an eddy-current absorber, or any other controllable device capable of absorbing power. Then it applies various factors air temperature, barometric pressure, relative humidity in order to correct the observed power to the value it would have been if it had been measured at standard atmospheric conditions, called corrected power.

Power to Drive a Pump In the course of working with lots of different engine projects, we often hear the suggestion that engine power can be increased by the use of a "better" oil pump. Implicit in that suggestion is the belief that a "better" oil pump has higher pumping efficiency, and can, therefore, deliver the required flow at the required pressure while consuming less power from the crankshaft to do so.

The Relationship Between Horsepower, Torque, and Acceleration | Daniel Miessler

While that is technically true, the magnitude of the improvement number is surprisingly small. How much power does it take to drive a pump delivering a known flow at a known pressure? We have already shown that power is work per unit time, and we will stick with good old American units for the time being foot-pounds per minute and inch-pounds per minute. Since flow is more freqently given in gallons per minute, and since it is well known that there are cubic inches in a gallon, then: Since, as explained above, 1 HP is 33, foot-pounds of work per minute, multiplying that number by 12 produces the number of inch-pounds of work per minute in one HPDividingby gives the units-conversion factor of Therefore, the simple equation is: When the equation is modified to include pump efficiency, it becomes: So suppose your all-aluminum V8 engine requires 10 GPM at 50 psi.

The oil pump will have been sized to maintain some preferred level of oil pressure at idle when the engine and oil are hot, so the pump will have far more capacity than is required to maintain the 10 GPM at 50 psi at operating speed. That's what the "relief" valve does: It is actually pumping roughly 50 GPM 10 of which goes through the engine, and the remaining 40 goes through the relief valve at 50 psi.