What Is Engine Balancing and Is It Necessary?

‘Balancing’ is a common term that you’ll hear whenever talking about car tyres, especially around a workshop. But what does it mean in the context of a car engine? Is engine balancing different, and is it necessary for your car?

Engine balancing means reducing the rotational, outward, inward, and reciprocating forces created by the moving parts in your engine. It is done by adding weights inside or outside the engine to counteract those forces. While it will reduce vibrations and noise, it will also cost you money and add to the vehicle's overall weight.

In this guide, we’ll give you an overview of engine balancing, how it works, and whether it is necessary or just a waste of time and money.

Engine Balancing, Meaning

To balance an engine means offsetting the weight of the moving parts and reducing vibrations and all the side effects that come with them. For instance, excess vibrations cause noise and reduce overall vehicle performance.

As we dive deeper into the topic of engine balancing, it’s helpful to think back to your physics classes back in school. That’s because the concept of balancing an engine means to counteract the physics of a combustion engine.

In this article, we’ll emphasize why keeping the engine balanced is crucial, and what’s involved in engine balancing.

What Does Balancing an Engine Do?

Engine balancing has the following benefits:

  • Increases engine efficiency
  • Provides tolerance to higher engine speeds
  • Ensures smooth running of the engine
  • Maximizes the engine’s lifespan

While your mechanic or automotive specialist may attempt to balance your engine, the fact is that no engine can be perfectly balanced. The process involves various complex factors, including the design and structure, weight and size, performance, efficiency, and many more.

What Does Engine Imbalance Mean?

We’ll get back to engine balancing in a bit, but first, what does engine imbalance mean?

We’ve hammered this many times, but we’ll say it once again – a car engine is made up of many parts. Some of these parts are stationary, while others have a specified motion. 

The motion of parts, like the pistons and connecting rods, creates an imbalance that causes vibrations when the engine is running. This automotive condition is what we refer to as engine imbalance.

One more thing to remember: The moving components have different motions, and to help analyse imbalance, you can broadly categorize these motions into three types.

Types of Forces that Need Balancing in an Engine

  • Rotational forces
  • Reciprocating forces
  • Outward firing forces

Let’s look at each force created and why they might require balancing.

Rotational Forces

You might already be familiar with RPM, which stands for ‘revolutions per minute’. That term represents how many times a crankshaft turns in one minute. For the average car, an idling engine rotates its crankshaft anywhere from 600 to 1,200 times per minute.

Interestingly, the crankshaft isn't always 100% balanced, creating an unbalanced rotational force that leads to vibrations and noise. The same is true with any other engine part that rotates, whether small or large.

For the average driver, that rotational force isn’t a problem. Still, if you want to get your engine balanced, that rotational force is one reason to do so.

Outward or Inward Firing Forces

Engines also have inward and outward firing forces, particularly those caused inside the combustion chambers. As combustion happens, those pistons will move inwards and outwards with a significant amount of power.

Considering how several pistons are doing that simultaneously, the force does cause a lot of vibrations inside the engine. Engine balancing can help eliminate some of these vibrations and reduce the noise that comes with them.

Reciprocating Forces

Lastly, the engine’s moving parts also create reciprocating forces. 

Let’s use the example of the pistons one more time. 

For inline engines, the vertical pistons and connecting rods move in a reciprocating manner. The combustion process works so that whenever some pistons are up, the others are down. 

Aside from the up/down movement, the rods also have a left/right action, but it’s the up/down motion that causes more significant vibrations.

Other components that create a similar type of force are pushrods and valves, following a similar sequence: when some are up, others are down.

Similar forces moving in opposite directions means that they are reciprocating or balancing each other out. While reciprocating forces generally cancel each other’s effects, there is often room for improvement using engine balancing.

Causes of Engine Imbalance

The following factors affect engine balance and are the major causes of imbalance.

1. Mass of the Engine Components

Uniform distribution of weight will help balance the forces caused by the different moving components.

Pistons or connecting rods with varying weights across the cylinders produce vertical forces as a result of the reciprocating motion. Likewise, uneven web weight can result in an imbalance from the rotation of the crankshaft or flywheel.

At low speeds, the vibrations may not be noticeable but will be as you accelerate.

2. Cylinder Layout

Even with a perfectly-balanced mass, imbalance may still occur as a result of cylinder layout. When the forces from respective cylinders fail to cancel each other out, it can cause a resultant force or vibration. 

For example, in an inline-four engine, the imbalance due to vertical vibrations is unavoidable but can be managed with the application of balancing shafts.

Types of Engine Imbalance

Engine imbalance can be any of the following:

  • Reciprocating plane imbalance – such as opposite parallel forces (called a couple) caused by the offset distance between the crankpins in a boxer-twin engine
  • Reciprocating phase imbalance – such as unevenly-spaced phases associated with V6 engines that lack an offset crankshaft
  • Rotating plane imbalance – commonly associated with a boxer-twin engine
  • Rotating phase imbalance – typically happens when a flywheel has irregularly-placed mass
  • Torsional imbalance – caused by torque applied at different distances (e.g., locations of the connecting rods) along the crankshaft

These imbalances can lead to reciprocating, rocking, and torsional vibrations. Torsional imbalance, for instance, causes torsional vibration that can weaken the crankshaft and eventually cause it to fail.

What Are the Methods of Engine Balancing?

As mentioned earlier, engine balancing involves adding weight to specific parts to counteract their movements. Doing that will bring things closer to equilibrium and reduce the forces that contribute to excess vibration and noise.

Steps to Balancing an Engine 

There are two steps involved in correcting an imbalance.

1. Static Balancing

The first step aims to ensure that the piston and connecting rod weights are even. Even loads result in equal inertia when these parts move.

2. Crankshaft Balancing

This step involves spinning the crankshaft independently to ascertain if there is a rotational imbalance. In case there is a rotational imbalance, weight is added or removed until a smooth rotation is achieved. Smooth rotation eliminates the vibration caused by rotational imbalance.

A balanced engine runs smoothly and can sustain higher engine speeds without getting damaged.

Internal and External Engine Balancing

Engine balancing can be done internally or externally. 

1. Internal Balancing

There are several ways to include counterweights inside the engine. One typical example is using an engine balancing shaft that works alongside the engine’s crankshaft.

Each balancing shaft is weighted unevenly so that each time it turns, it cancels out the other forces mentioned above. Of course, the exact weight of each balancing shaft will depend on what’s necessary to achieve that outcome, so not all cars will use the same weights.

The balancing shaft is connected to the crankshaft using a pulley that ensures both shafts turn together simultaneously.

2. External Balancing 

You can also balance your engine externally. For example, adding weight to the engine’s harmonic damper can counteract the forces created inside the engine.

When the crank's counterweights are not heavy, the engine has to be balanced by adding weight to the external part, such as the flywheel.

Of the two, internal balance is the preferred option since external counterweights have a flexing effect on the crankshaft at high engine speeds, which can cause engine damage. Most engines, however, can be balanced both internally and externally.

However, switching from external to internal balancing is costly as it needs you to acquire a new crankshaft, harmonic balancer, or flywheel. It is recommended to balance the engine in the same way as the factory did.

What Are the Pros and Cons of Engine Balancing?

Now, we’ve come to a crucial question: Most cars already manage their vibrations and noise, so why is engine balancing even necessary?

Well, engine balancing offers these benefits. 

Pros of Engine Balancing

  • First, balancing reduces the amount of energy wasted inside an engine.
  • Less wasted energy means balancing improves fuel and energy efficiency.
  • That also leads to more engine power.
  • Simultaneously, there are fewer vibrations and less noise.
  • Overall, balancing creates a smoother-running engine.

All those advantages sound fantastic, but you’ll also want to consider the drawbacks of this process.

Cons of Engine Balancing

  • Added weight - Remember: balancing is mostly about adding counterweights to reduce the forces created inside the engine. Extra weight means the engine has to work harder to move the vehicle, ironically reducing its fuel efficiency.
  • Extra cost - There are plenty of different upgrades you can invest in for your car. The cost of engine balancing might not be worth it for many drivers.

How Much Is Engine Balancing?

The price for engine balancing cost will differ between engine types. Still, you can expect to pay a few hundred dollars to get the job done, and it’ll likely take a few hours to complete.

To give you an idea of what you might have to spend, one workshop we looked at charges approximately $270 to balance a standard V8 engine.

Is Engine Balancing Worth It?

Probably not. For most people, engine balancing doesn’t offer that much difference to your daily driving experience.

Remember: The manufacturer already balanced your car engine before it came out of the factory, at least to some extent. But of course, the manufacturer balanced the engine with normal road use in mind, not for high-performance situations.

The only situation where balancing could be worth it is if you’re modifying your engine and are trying to get every ounce of high performance out of it. In that kind of situation, perhaps engine balancing could help you get a little bit more power from your engine.

 

(Blog from carpart.com.au)

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