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Summary
  • Boxer engines are a type of flat engine with a cylinder bank angle of 180 degrees. The term “boxer” comes from both the shape of the engine and the way its pistons move symmetrically in pairs. This results in the pistons “punching” like a pair of boxers.
  • The advantages of boxer engines include lateral stability and decreased roll, smooth acceleration, and positioning. Disadvantages of boxer engines include their price, limited service, and unique design.
  • Manufacturers who use boxer engines include Porsche, Subaru, and Toyota.

Boxer engines are an uncommon engine variant with an interesting design and mechanic. They have different benefits and drawbacks, and any buyer looking to purchase a vehicle with a boxer engine might want to learn more about them before signing that dealership contract.

You might be wondering though, “What is a boxer engine?” Let’s take a look.

Boxer Engines Explained

When it comes to this unique engine’s name, the term “boxer” comes from both the shape of the engine and the way its pistons move. The pistons in a boxer engine move symmetrically in pairs thanks to the engine’s firing order. This results in the pistons “punching” like a pair of boxers.

Now, in terms of build, boxer engines are a type of flat engine. Like other flat engines, boxer engines have a cylinder bank angle of 180 degrees. A cylinder bank angle is the angle between two nearby connecting rods, and when the angle is at 180 degrees, it results in a flat look for the engine. In comparison, the typical inline engine has a cylinder bank angle of 0 degrees, making it stand somewhat vertically. V engines have 90-degree angle, and VR engines have 90- or 15-degree cylinder bank angle. This gives them their signature “V” shape.

The cylinder bank angle affects the engine’s firing sequence, vibration, and performance. In the case of flat engines, because the pistons are horizontally opposed with the crankshaft in the middle, the pistons reach the top of the stroke simultaneously. This results in balanced momentum.

While all boxer engines are flat engines, not all flat engines are boxer engines. Unlike other flat engines, boxer engines have individual crankshaft journals for each piston. The journal is the point where parts bolt together, and in boxer engines, each cylinder of the engine has its own individual connection point.

close up shot of a boxer engine
Boxer engines are a type of flat engine and have a cylinder bank angle of 180 degrees.

Advantages and Disadvantages of Boxer Engines

Thanks to their design, there are things that boxer engines do well. At the same time, there are a few struggles that come with owning a boxer engine.

Advantages

Lateral Stability and Decreased Roll

Compared to inline and V-type engines, boxer engines have a squatter, more rectangular shape. This low, flat form factor allows the engine to sit lower in the vehicle, which gives the vehicle itself a lower center of gravity. This means going around corners and performing other maneuvers with a boxer engine will have less roll and more lateral stability. The vehicle is more balanced as a result and easier to handle.

Smooth Acceleration

Because the pistons on a boxer engine fire horizontally, they balance the engine as they fire. Compared to inline engines and V-type engines, which fire at angles or horizontally, the boxer engine vibrates less as a result, leading to smoother acceleration.

Positioning

The shape of a boxer engine makes it easier to position in the engine bay. It can sit lower and farther into the compartment, nearer the firewall for any hazardous accidents. In case of an accident, the engine is more likely to be shoved beneath the passenger compartment rather than into it, thanks to where it sits in the engine bay. A box engine’s positioning also improves the vehicle’s balance, making it easier to handle.

Disadvantages

Price

Boxer engines tend to be more complicated to manufacture than inline and V-type engines. They also have more components, making them a pricey investment for manufacturers. This is why vehicles powered by boxer engines can be relatively rare.

Limited Service

Because they’re not as common as inline and V-type engines, it’s also harder to find mechanics who are familiar with boxer engines. This limits the service options for any vehicles running on them. A boxer engine’s layout makes it difficult to reach certain components, meaning some do-it-yourself projects might have to be done by a mechanic instead. The smaller size of a boxer engine also makes it difficult to work on. This is especially true when there’s not a lot of space under the hood to begin with.

Unique Design

You’d think that uniqueness would be a good thing, but because of how the boxer engine is designed, it won’t just fit any vehicle. To make them work well, Subaru in particular needed to put a lot of research and development into the engine bays of their high-volume boxer engine-powered Ascent SUVs.

Subaru Issues

Specific boxer engines might also experience their own unique issues, such as the EJ25 found in certain Subaru models. These boxer engines have been known to suffer from head gasket problems and externally leaking coolant.

What Manufacturers Use Boxer Engines?

If you’re looking for manufacturers offering boxer engine cars for sale, check out Porsche, Subaru, and Toyota. These manufacturers develop their own four- and six-cylinder boxer engines separate from each other.

Apart from their all-electric Solterra SUVs, Subaru uses boxer engines for all their vehicles. Porsche has their boxer engine design in their Boxster, Cayman, and 911 models, and Toyota offers their boxer engine in the Toyota GR86.

Boxer engines are a fascinating option for those looking for a stable and smooth ride. That said, these engines are limited to a few select vehicles for now, and they can pose a few difficulties when it comes to repair and maintenance. Keep all this in mind before making your purchase, and check out the other available engine types before deciding on which one to buy.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at CarParts.com

Tony Harlin is a Master Gas and Diesel Diagnostic Technician with over 18 years of experience. He works full-time at a large independent automotive shop as a driveability and repair technician working on all types of vehicles with a focus on diesels. ASE certifications include A1-A9, L1 and L2, as well as X1.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

File Under : Engine , DIY
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