# Turning Moment of Single Cylinder 4-Stroke Engine | Explanation

• Athi Sankar
In summary, the Turning Moment diagram of a Single Cylinder four stroke Engine shows the net force acting on the piston to be a result of gas pressure, inertia, and friction. The positive turning moment at the end of the suction and exhaust strokes is due to the momentum of the gas flow in the inlet and exhaust ports. By tuning these ports, the momentum effect can be enhanced to increase engine power and improve exhaust and inlet gas mixing.
Athi Sankar
TL;DR Summary
Theoretical turning moment diagram for an four stroke engine has the positive turning moment at the end of suction and exhaust stroke.

Figure 1 shows the Turning Moment diagram of Single Cylinder four stroke Engine. Can anyone tell me, how the turning moment becomes positive at the end of suction and exhaust stroke.

Net force F = Force due to gas pressure - Inertia Force - Reaction Force due to friction

If the net force acting on the piston (F in fig (2) ) becomes positive then only the piston moves towards right side. e(i.e) During expansion stroke the torque will be developed at the crank shaft. Excess Energy stored in flywheel. This excess energy releases whenever the torque is negative to maintain constant output. But as per the fig (1) at the end of suction stroke there is some positive torque can you say the reason?

I believe you are seeing the momentum of the gas flow in the inlet and exhaust ports.

The induction stroke starts out drawing air through the inlet port into the cylinder. The velocity rises at first but when the piston slows down there is an over-pressure due to the momentum of the induced air.

During the exhaust stroke the gasses accelerate into and along the exhaust port. As the piston slows down, there is a partial vacuum drawn due to momentum of the escaping exhaust gasses.

By tuning the inlet and exhaust ports the momentum effect can be enhanced to draw in more air and to expel more exhaust. That gives more engine power and less mixing of exhaust and inlet gasses.

Athi Sankar
Thank you

## 1. What is the turning moment of a single cylinder 4-stroke engine?

The turning moment, also known as torque, is the measure of the rotational force produced by the engine. It is the force that causes the crankshaft to rotate and is measured in units of Newton-meters (Nm).

## 2. How is the turning moment calculated?

The turning moment can be calculated by multiplying the force applied to the piston by the distance from the center of the crankshaft to the point where the force is applied. This distance is known as the crank radius or crank arm.

## 3. What factors affect the turning moment of a single cylinder 4-stroke engine?

The turning moment is affected by several factors, including the size and design of the engine, the fuel-air mixture, and the speed at which the engine is running. Additionally, the compression ratio, ignition timing, and engine load can also impact the turning moment.

## 4. Why is the turning moment important in engine performance?

The turning moment is crucial in determining the power and efficiency of an engine. A higher turning moment means the engine can produce more power and torque, which translates to better acceleration and overall performance. It also affects fuel efficiency, as a higher turning moment can result in better fuel consumption.

## 5. How can the turning moment be improved in a single cylinder 4-stroke engine?

The turning moment can be improved by making changes to the engine design, such as increasing the size of the cylinder, adjusting the compression ratio, or optimizing the fuel-air mixture. Additionally, proper maintenance and tuning of the engine can also help improve the turning moment.

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