Diesel Engine Horsepower

In diesel engines there are some important parameters that determine the performance of diesel engine Horsepower, that is torque and power for more details how to calculate it as follows:

In the engine component, the force is represented by the load, the distance represented by the length (radius/arm) on the dynamometer, or the center point distance of the main journal towards the pinpoint of the journal crankshaft), then the time represented by the speed (rotation per minute/rpm).

The force multiplied by the engine speed is expressed as torque, so torque can be expressed: 
Torque = Force x Speed

Then the engine power can be written with the formula: P = T x S


P = Power (power)

T = Torque (torque)

S = Speed (rpm)

The third is what will determine the diesel engine specs of a machine that will be in use

Power (Horsepower)

The average work is measured by end power (The torque of the crankshaft drives the diesel engine but this is just a force for diesel engine driving and the speed at which the diesel engine is driven is not taken into account.) Power is the speed at work.

Unit of Power

PS (Prerd strarke in Germany) 1 PS - 75 Kg m /sec is power to move an object weighing 75 Kg as far as 1 meter in 1 seconds (the greater the power the greater the amount of unity work time).

Diesel Engine Horsepower
Diesel Engine Horsepower


The rotary force on the rotating part is called Torque, the engine is driven by the torque of the crankshaft.

Torque = force x distance

The more the number of teeth on the gears, the greater the torque that occurs. So the speed is reduced to half.

Maximum Torque

The maximum torque of each diesel engine varies. When the diesel engine works with maximum torque, the rear wheel motion is also maximum. The greater the torque, the greater the power of the diesel engine. The amount of torque is usually included in the technical specification data, service manual or in a marketing brochure of a diesel engine product.

Piston Speed

As the engine rotates, the speed of the Piston at the TDC (Top Dead Center) and BDC (Bottom Dead Center) is zero and at the center is faster, therefore the piston speed is taken on average.

From the BDC, the piston will move back upward because of the crankshaft rotation, thus at 2x the piston movement, will produce 1 turn of the crankshaft, if the crankshaft makes N rotation, then the piston moves 2N round. Because it is expressed in seconds then divided by 60.

The relationship between engine speed and horsepower (Power)

Engine power varies depending on torque and engine speed. Machines with high rotation, usually the power generated is also great resulting in the highest horsepower diesel engine but if the rotation is too high the power generated will decrease.

If at a certain turn of maximum power is generated, then it is called "Maximum power".

If a shaft rotates once a minute it can be stated that the shaft rotates 360º / min. If it rotates 3/4 turns in one minute, it can be expressed by 0.75 rotate/min. or 270º/min.

Can be expressed by: 1 turn = 360º = 2π radians

If the speed is 1 rotation /minute = 2π x n / min ............ or in 1 rotation /sec = 2π x n / 60.

1 PS = 75 kgm / sec

1 HP = 76.04 kgm / sec

Since the engine rotation speed is normal with rotation per minute (rpm), it should be converted to rotation per second, so it becomes:

P = T x S

P = T x 2π x n / mnt, to be:

P = T x 2π x n / 60 ........ to make in units of kgm / sec.

So that the power in the HP (Horsepower) unit, obtained the formula:
HP = (T x 2π x n) / (60 x 76.04)
HP = (2π: 4662,4) x T x n
HP = 0,001376 x T x n

In units of PS, obtained the formula:
PS = (T x 2π x n) / (60 x 75)
PS = (2π: 4500) x T x n
PS = 0.001396 x T x n

An example of using a formula, if known from a diesel engine performance graph, the engine has rated the power of 320 HP at 2000 rpm, the torque rated is obtained:

HP = 0,001376 x T x n
HP rated = 0.001376 x Torque rated x n
320 = 0.001376 x T x 2000
Torque rated = 320: (0.001376 x 2000)
Torque rated = 116 Kg.m

I think that's all about diesel engine horsepower, hopefully, easy to understand and add your insight.

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