Flywheel Guide: overview and common questions

Flywheel is a word nearly everyone has heard. You must have thought, at least once, that flywheels were only found in planes. The 'fly' in the 'flywheels' makes the assumption likely. Well, they are found in, but not limited to, airplanes, and their presence in planes is not why they were so named.

Car engines are at their most efficient when they generate mechanical power at a uniform, generally high speed. Any vehicle that can achieve this at all times will be at almost 100% efficiency.

However, this is not possible. Automobiles and the engines they carry can only operate at different kinds of speeds. Often, in fact, they will eventually need to stop. But clutches and gears solve some of this challenge.

flywheel, clutch plate, and clutch disc

As a mechanical switch, a clutch allows a car to disengage itself from its engine. Meanwhile, a gear is a pair of intertwined wheels with teeth that varies the turning force (torque) and speed. This is to enable the engine to run slower or faster even when the engine maintains a uniform speed.

However, what clutches and gears can't do is save power wasted during braking and use it to work later. Flywheel performs this job. A flywheel is one of the most important components of a car engine.

And in this article, we have, again, enlisted the expert help of our professional mechanic to discuss it. This article will cover flywheel definition, how it works, functions, as well as symptoms to look out for in a faulty one. We will also be answering some frequently asked questions about the component. Let's begin.

Flywheel overview

To fully understand what it is and its function in vehicles, we will start from the beginning.

What is the flywheel in a car?

A flywheel is a heavy mechanical device typically affixed to the rotating shaft. It works to smoothen power delivery from a motor to a car engine. Its tendency to remain at rest or continue in motion (inertia) opposes and manages fluctuations in engine speed.

The car flywheel stores excess rotational energy (a form of kinetic energy) for subsequent intermittent use in starting engine or speeding. To put it simply, a car flywheel is a teethed plate that is mounted to the crankshaft at the rear of the engine.

flywheel attached to crankshaft

Flywheel construction material

Flywheels are, by design, tough and long-lasting. A car flywheel is typically made of steel and made to rotate via conventional bearings. However, high energy density flywheels that revolve at speeds of up to 60,000 revolutions per minute (1 kHz) are constructed differently using carbon fiber composites. And they run on magnetic bearings.


Where is the flywheel located?

The flywheel is attached to one end of the crankshaft. It precisely sits in-between the transmission (gearbox) and the engine. Also, it is positioned in such a way that it is in contact with the key starter - the component that starts the engine.

How does the flywheel work?

First things first, the wheel works to store energy for future use. In a way, it’s similar to a mechanical battery mechanism. While batteries store power in the form of a chemical, flywheels conserve energy in kinetic energy form. A car flywheel can store more energy if it moves at a considerably higher speed.

This usually translates to more bulkiness, However, spinning the wheel faster is better than increasing the mass. For instance, a flywheel will generate two times the energy of another that weighs half as much, with both speeds being equal.

Whereas, spinning the less bulky wheel twice as fast will generate four times the amount of energy stored. Fetching from this, it’s more efficient to use a light wheel that spins at high speed than bulky ones.

Functions of the flywheel in a car

They are found in nearly all types of automobiles, from SUVs to race cars to buses. Wherever you find them, they are there to serve the following functions:

1. Starting the engine

A flywheel helps to start the engine. The gear teeth on it cut into the circumference support which starts the engine. Here’s how it goes: A small gear, also known as the Bendix gear, connects with the wheel as you turn your ignition.

The Bendix gear spins the flywheel by turning the crankshaft. This will commence the compression cycle required to kick start the engine. The Bendix gear retracts as soon as the engine starts to enable the wheel to spin without hindrance.

bendix gear, Kickstarter

2. Balancing the engine

Vibration and wobbling occur often because the pistons are offset from the crankshaft's middle. This is mainly because each piston fires at different angles. The flywheel, however, buffers the side-to-side movement. It decreases the general engine's vibration, stabilizing and balancing it on the mount. The wheel achieves this due to its bulky weight.

3. Smoothing engine speed

As you know, the crankshaft converts the oscillatory movement of the pistons into rotary motion when the engine starts. Nevertheless, the resulting motion is jerky as it produces power. Here, the flywheel bulk employs inertia to keep the crankshaft turning between every piston firing. Like this, the speed of the crankshaft's rotation is constant, allowing the engine to operate smoothly.

4. Reducing drivetrain stress

Recall that the flywheel stabilizes the engine's movement and smoothing out its speed. By doing this, it helps to reduce wear and tear on the components of the drivetrain.

5. Determining engine build

The performance of an engine relies on the weight of the flywheel. The rule of thumb is that big vehicles go with bulkier flywheels and smaller automobiles like race cars will do fine with lighter flywheels.

Can a car flywheel go bad?

bad flywheel

Unfortunately, yes, they can and they often do. Like all car components, flywheels aren't built to last forever. With time, they tend to gradually wear and tear continuously to continuously use.

How can you fix the flywheel when it goes bad?

In most cases, you will have to replace your flywheel when it’s bad. Here’s how you can replace it: First of all, find the center of the wheel where it’s held in place by the remaining bolts. Use a wrench to remove them.

fixing a flywheel when it goes bad

Remove the flywheel bolts[/caption]Then, lift the damaged flywheel from the crankshaft. Do this by pulling it away. Now, replace it with the new wheel and put the bolts. Make sure you tighten it firmly. Please note that while it seems simple here, the process is a frightfully tedious one. So, you should let a professional do the job.

Can a faulty flywheel spoil the engine?

Eventually, a bad wheel will pack up your car. The reason is that flywheel complications go on to cause subsequent damages to other car components of the clutch and the crankshaft. Sometimes, it can even cause your engine to fail.

Is it expensive to replace a flywheel?

Yes, but flywheels are not expensive, it’s the workmanship costs a lot of money. Here’s why: The process of replacing them is incredibly tedious and awfully time-consuming. The labor cost alone can be as high as $400 and more. In the end, you may have to pay anything between $500 and $1,000 to replace a bad one.

Symptoms of a bad flywheel

So far, we have established that flywheels can go bad just like any other car part. How then do you know when your flywheel is going bad or has completely been damaged? To help you answer this question, the following are major signs that occur when a flywheel is damaged:

1. Clutch will start to slip

slipping clutch

This is arguably the most common issue. When this happens, your gear will slip as you try to change gears when driving. It indicates that insufficient or no power reaches the wheel. It will consequently wear the clutch.

The slipping clutch eventually damages the flywheel too. A disturbing grinding noise often soon suddenly follows, implying that the pressure plate and other wheel components are overheating. The result is warping and cracking.

2. A burning smell

A noticeable acid smell usually indicates that the clutch isn't working properly. This is typically due to a damaged flywheel or a bad driver. The faces of clutches are built with materials that work to reduce the noise the clutch generates during work. These materials generate high heat as a result of friction that may occur as a result of improper use of the clutch.

3. Clutch may also drag

Clutch drag

This issue is similar to clutch slipping, but the opposite. In this case, the clutch in question won't release completely. In rare instances, it won't even release at all. This typically results in different degrees of grinding when you try to change gears.

What's more, you may not be able to put your car into first gear after starting the engine. It is important to note here that clutch dragging isn't a direct symptom of flywheel damage. Instead, it's the fault of the bearing in the flywheel. So, it's technically (and indirectly) a flywheel issue.

4. Chattering of clutch

You will notice this symptom when you try to engage the clutch. Instead of engaging smoothly, it would skip around the flywheel, as it holds and releases the flywheel continuously.

The release will vibrate, feeling almost like a stutter. While it can happen in any gear, it's more often seen in cars starting from rest. The issue is usually a warped flywheel.

Also, it could just be the pressure plate, the clutch disc, or the release bearing that is at fault. They may be worn, warped, or broken. This can make it difficult to diagnose. A professional mechanic would come in handy here.

5. Vibrating clutch pedal

Your car flywheel is probably damaged if you notice the clutch pedal vibrating. The spring mount is the precise part of the flywheel that is responsible for this symptom. This diagnosis is simple because the spring mount mechanism normally reduces the vibration produced as you use the clutch.

Frequently asked questions about the flywheel?

This section attempts to answer some of the common questions that are often asked about the flywheel. Let’s begin!

Does a car need a flywheel?

Yes, all cars do. The singular fact that a flywheel is in every car proves this.

Does the flywheel spin in neutral?

No, the flywheel doesn’t spin in neutral. The reason is this: the clutch is connected to the wheel when the transmission is in neutral. The flywheel, however, starts to spin when you release the clutch pedal.

Does the flywheel add horsepower?

No. A car flywheel can't add horsepower. Instead, it ensures that the already existing horsepower is readily available by allowing for quicker throttle response and reduce drivetrain loss.

Can a car move in neutral?

No, it won’t. When in neutral, the transmission from the car engine can’t reach the differential and thus can’t carry power to the wheels. No power, no movement.

What happens if the flywheel breaks?

Several things can happen, but the most common one is your car losing power altogether.

Flywheel in a diesel engine vs. in a petrol engine

Flywheel in a diesel engine vs. in a petrol engine

Flywheels perform the same functions in both gas and diesel engines, but they go about it a bit differently. For one, the wheel for diesel engine vehicles is generally larger than those in petrol engine cars. Apparently, the greater bang in the former requires a larger wheel moment of inertia. What’s more, the additional stored energy that results from this is needed by the engine to complete its compression stroke.

How to prolong the life of a flywheel

To keep your wheel working for as long as possible, strictly adhere to the manufacturer’s maintenance guidelines. This is a no-brainer. Clean and replace cabinet air filters and flywheel bearing assembly when due.

Final word

As you have seen, Flywheel is an essential component in every automobile; petrol and diesel engine vehicles alike. We have taken the time to carefully break down the flywheel and how it works.

The article also discussed the various functions of flywheels in vehicles and the materials manufacturers use to construct them. Since flywheel, like other car components, is prone to damage, the article also touches on signs to look out for. We have also clearly answered some frequently asked questions.

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