What Does A Flywheel Do In A Car? (All You Need To Know)

All vehicles have their flywheel. When we say flywheel, it is a heavy metal disk. The diameter is about twelve (12) to fifteen (15) inches. In its circumference, there are gear teeth cut into it. 

So what does a flywheel do in a car? Each component of a vehicle has its functions and they contribute to the operation of every vehicle. A flywheel helps in starting your engine, smoothens the engine speed, balances the engine, reduces drivetrain stress,  and its weight helps.

Flywheels are linked to the rear of the crankshaft. They are in between the engine and the transmission. Flywheels are also called flex plates linked to the automatic transmission. 

With that, it will be lighter than the flywheels used with the manual transmission. This may be a standard vehicle component, but many people still do not know so much about this. And as a car driver, it is essential for you to know about the components of your vehicle like the flywheel. 

With that, many car drivers are asking what a flywheel does in their vehicle and so in this article, let us enlighten you about the function of a flywheel. You can refer to this article for your guide. Let us start.

What Does A Flywheel Do In A Car

What Is The Purpose Of A Flywheel In A Car?

Each component of a vehicle has its functions. They contribute to the operation of every vehicle. These are the purposes of a flywheel in your vehicle.

1. Starting Your Engine

The gear teeth will cut into the flywheel’s circumference providing help in starting your engine. The starter motor of an engine has a small gear. This small gear is called a Bendix gear. 

This will mate up to the flywheel if you turn the key. The Bendix gear or the starter motor combination will spin the flywheel. 

After spinning the flywheel, it will turn the crankshaft and start the compression cycle needed to start an engine. If the engine has not started, the Bendix gear will withdraw so that the flywheel can spin freely.

2. Smoothens The Engine Speed

If the engine has started, the crankshaft will convert the up and down motion of the piston into a circular motion. But this motion will jerk because the power will generate twice only in a four-cylinder engine. It can also be four times for an eight-cylinder in one engine revolution. 

So the mass of the flywheel will use inertia to keep the engine crankshaft to turn between each piston firing. With that, the rotation speed of the crankshaft will be constant, thus making the engine run smoothly.

3. It Balances The Engine

The pistons are offset on the center of the crankshaft. With that, the engine will vibrate, and it will giggle too if each of the pistons will fire at a different angle. However, the heavyweight of the flywheel will resist a side-by-side motion, and it will help stabilize and then balance the engine in its mounts/ it will also reduce the vibration throughout the vehicle.

4. It Reduces Drivetrain Stress

The flywheel will decrease tear and wear on the other drivetrain components if you stabilize the engine’s movement and smooth its speed. For example, even if the engine and the transmission sites are parallel, the attachment hat is between the transmission and the axle. The flywheel will remove the wear in these joints. 

5. Its Weight Helps

The weight of the flywheel is an adjustment custom engine builder and is used to tailor the engine’s performance for specific uses. For example, a heavy flywheel will help the engine work under heavy loads. 

On the other hand, the engine running at high speed like race car vehicles will benefit from a lighter flywheel. This is because it can improve the acceleration in speed, and it can be harder to keep the engine. 

What Does A Flywheel Do In An Engine?

A flywheel is a heavy wheel, and it is linked to a rotating shaft. It will smooth out the power delivery from the motor and into a machine. The inertia of the flywheel will oppose, and it will modify the fluctuations of the engine’s speed. 

A flywheel is given high rotational inertia to oppose speed fluctuations effectively. A wheel with a heavy rim linked to the central hub by spokes or a web has very high rotational inertia. A lot of flywheels are used to have a reciprocating engine to smooth out the flow of the power. 

What Does A Flywheel Do In A Small Engine?

The flywheel wrench is a rectangular metal pin, and it will align the crankshaft and the flywheel and tighten the flywheel nut simultaneously. Unfortunately, the flywheel wrench can break and protect many expensive parts of the cutting knife that hits the object strongly. 

Your engine’s flywheel is made originally to store the combustion engine and keep the crankshaft that is moving in between engine strokes. This is because the flywheel on a small engine has so many functions. 

What Does A Flywheel Do In A Clutch?

The clutch has plenty of components, and they all play an essential part in the operation. For example, the flywheel has three main functions. The first function maintains a rotating mass or what we call inertia to assist the engine rotation. 

It will also provide more consistent delivery of torque during running. The second function provides a ring gear for the starter motor to engage. And the third function is to produce one of the driving friction surfaces for the friction disc. 

What Does A Flywheel Do In A Manual Transmission?

A flywheel is a metal disc. It resembles a gear that is positioned between your clutch and the transmission. Along with the clutch, this part helps to provide power to and from the engine and the transmission. Any manual automobile, heavy-duty truck, or big rig has this part.

How Does A Flywheel Work?

A flywheel is very important to the mechanical battery that has a mass rotating around the axis. A flywheel will store energy in a kinetic energy form, and it will work by speeding up the rotor to a very high speed. It will also maintain the energy in the system as rotational energy. 

A flywheel energy storage is an outstanding and reliable technology, and it has replaced the conventional lead-acid batteries in energy storage systems. Many modern high-speed flywheel energy storage systems have a substantial rotating cylinder supported on a stator. 

Where Is The Flywheel Located?

The flywheel in your vehicle is located towards the rear of the engine, and it is directly between your engine and your transmission. Therefore, the housing will be complete, and it will encase the flywheel, and you will not see the whole thing until you remove the transmission of the engine. 

What Are The Advantages And Disadvantages Of A Flywheel?

Flywheel has its advantages and they also have its disadvantages. It is listed below.


  1. It Has A Fast Power Response 
  2. The Recharge Time Will Be Short
  3. The Power And The Energy Are Almost Independent
  4. It Has A Potential High Specific Energy
  5. It Has A High Cycle And Calendar Life
  6. It Has A Relatively High Round Trip Efficiency


  1. It Has A Short Discharge Time
  2. The Complexity Of Durable And Low Loss Bearing
  3. There Is Mechanical Stress And Fatigue Limits
  4. The Material Has A Limit Of Around 700m/Sec Tip Speed
  5. It Has Potential Hard Failure Modes
  6. It Has Relatively High Parasitic And Intrinsic Losses

How Does The Flywheel Differ From The Governor?

The flywheel and the governor are mechanical devices, and it is used mainly for one purpose: to control the fluctuations in speed except for the impact. If the flywheel regulates the speed variation in the crankshaft, the governor will control the variable speed from the load variation. 

The difference between flywheel and governor is operating if the engine runs and continues from cycle to cycle. In contrast, the operation is intermittent in the case of the governor. It means that it will only operate if the engine will not run at its speed.


In summary, many people have been asking about the function of the flywheel. Flywheel is an atypical part of every engine. 

Some car drivers do not even know about it, but it is there. It has a lot of conditions. It also has a lot of advantages that can offer to the vehicle.

Also Read:


Image credits – Canva

Share on:

My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more