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All You Need To Know About Boxer Engine

When speaking of car engines, you’ve probably heard of the boxer engine. Are you curious about it? Want to know why it’s called boxer and how it works? Follow me and I will show you what you need to know about it.

What is a Boxer Engine?

The boxer engine is a flat engine, belonging to the type of internal combustion engine. The engine pistons are arranged horizontally and symmetrically on each side of a central rotating crankshaft. When operating, they move continuously and in opposite directions, transfer force to the crankshaft, helping the crankshaft to move. It’s called “boxer” because the way the pistons move is like a boxer throwing punches.

The Boxer engine was invented by Karl Benz – the founder of the Dalmer group and the world-famous Mercedes-Benz car company – in 1896. In 1899, the boxer was officially launched with the name “contra/kontra engine”. Currently, the boxer engine has been greatly improved, applied in the aviation, locomotive, and automobile industry. Currently, two car manufacturers use boxer engines in their cars are Porsche of Germany and Subaru of Japan.  Especially, Subaru has used boxer engines in its cars ever since 1966 until now.

Advantages of the boxer engine

The boxer engine has some outstanding advantages below

High performance

Due to the flat structure and horizontal mechanism, the boxer engine can be arranged in line with the driveshaft and gearbox more easily. The force generated by the piston movement is transmitted to the crankshaft to the gearbox and the wheels more directly, requiring fewer transmission components than an I or V construction. Therefore, the engine will have higher efficiency because less power is wasted through the drive gears.

Stability

The symmetrical horizontal structure of the boxer engine and the opposite, co-planar motion of the pistons create opposite forces, so the engine itself will suppress vibration better than other structures. As a result, we have an engine block that works smoother and less noisy. Not only that, because the oscillation force is smaller, the engine parts suffer less wear and tear, resulting in a longer lifespan of the engine.

Low center of gravity

The boxer engine has a flat structure and horizontal cylinders, so its center of gravity will be lower, which means that the center of gravity of the entire car will also be lowered because the engine is one of the heaviest components of the vehicle. The lower the center of gravity, the more stable the vehicle will be when operating at high speeds. Because the pistons are evenly arranged on both sides of the crankshaft, the weight of the engine is also evenly divided, so the car is very stable when turning a corner.

Safe

When a collision occurs, sometimes the force of the collision is so strong that it pushes the engine back to where the driver is and causes injury to the driver and passengers. The boxer engine is low and flat and is located below the front compartment. Therefore, if a collision happens, the engine will not cause serious injury to people.

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Disadvantages of Boxer Engine 

You must be curious as to why the boxer engine is so good but not as popular as other I, V engines. This is also due to some disadvantages of boxer engines.

Size

Because of the horizontal cylinder arrangement, the boxer engine is wide in width and low in height. With such a structure, it requires a different and more complex chassis to be able to arrange the engine neatly. Redesigning the chassis is not as easy as it sounds, not only to fit the engine in but to ensure the car’s efficiency when driving and still look beautiful.

High cost

Similar to the V-shaped engine, the Boxer engine requires two cylinder heads, which means more components are needed in the machine. The boxer engine has a complex overall structure with many details, so the machine parts must be compact to maximize the engine’s width. That’s why most cheap cars use I engines with inline cylinders. Both the research and production costs of boxer engines were higher than other engines.

In addition, due to the complexity and location of the engine, you need to find mechanics who specialize in boxer engines to repair and maintain when needed, not all mechanics can do it. The engine is located deep in the engine compartment, that is why if you want to fix it, you have to remove a lot of parts out of the way first. This also leads to higher maintenance costs. Vehicles with boxer engines require more maintenance than others.

car with boxer engine
Source: Porsche

Difficulty in increasing capacity

For boxer engines, the only way to increase power is to increase the diameter of the cylinder bores. If you can not extend the cylinder stroke because the width will be larger, create difficulties in the process of designing the engine compartment. When the engine is “oversquare”, meaning the cylinder diameter is larger than the stroke of the piston in the cylinder, combustion efficiency will decrease.

Some other problems that often mentioned are leaky head gaskets (because the cylinder is horizontal, so the liquid in the cylinder is easy to leak out),  the cylinder is worn on one side because the pistons move horizontally under the impact of gravity,…

Conclusion

The disadvantages of the boxer engine are not much but still hinders it from appearing in high-end cars. It is not very attractive when both the price of the car and the cost of maintenance are high. However, many famous car models use this boxer engine you can refer to, such as Ferrari Testarossa, Porsche 911, Subaru Impreza STI, etc… You should consider which engine type is suitable for your needs and your own conditions when choosing to buy a car.

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