Two-stroke boxer engine. Boxer engine: types, device and principle of operation

The boxer engine is not just a technique that was ahead of its time, but in fact the solution to many problems that many modern traditional engines cannot solve.

What is a boxer engine? Video

The boxer engine is a special type of power plant that resembles a traditional engine itself, but the cylinders are located horizontally. In common people, this motor was called "boxer". This is due to the movement of the pistons from each other, or towards each other, towards each other. However, the two pistons are in the same position.

Boxer engine. Photo

The first example is an engine from Volkswagen in 1938. At that time, the unit consisted of a 4-cylinder "boxer" with a volume of 2 liters, with a capacity of 150 horsepower. After that, the motor gained popularity and began to be widely used.

Subaru boxer engine

Today, boxer engines are manufactured and installed by Subaru and Porsche. Until recently, Toyota, Honda, Ferrari, and, of course, the founder of boxer engines, Volkswagen, also shared this fate. Such installations can be seen not only in motorcycles, Ikarus buses, but also in some tanks.

Video about the Subaru boxer engine:

The principle of operation of the boxer engine. Video

To form a final picture of what a boxer engine is, you need to understand its structure. Let's repeat what was said earlier - this is an internal combustion engine, which has one feature - the movement of a pair of pistons is performed in a horizontal plane ... The second pair in the neighborhood is also in a horizontal position.

The total amount of such cylinders can reach 12, of course, counting starts from 2. The number will necessarily be a multiple of two. The most popular designs are 4 and 6 cylinders. Experienced mechanics and professionals have noted that the operation of the 2 and 4-cylinder boxer is not too different from the traditional engine. The peculiarities begin to appear starting from six cylinders.

Video of the principle of operation of the Subaru boxer engine:

A variety of boxer engines

It will not be news that the very principle of operation depends on the features of the type of unit. This also applies to boxer engines.

They are divided into:

1. Boxer boxer, which are often used in Subaru cars. As for the principle of their operation, it should be said that the pistons are located at a predetermined distance from each other, at the same distance from the engine axis. But at the same time, each piston is located separately from each other in the cylinders. This principle of operation is similar to boxing fights, hence the name;

   
   Boxer engine - boxer. Photo

2. OROC radically different from the boxer, both in structure and in the sequence of pistons. These units are two-stroke. One of the cylinders is located just behind two pistons that are attached to a single crankshaft. One of them is responsible for the intake of the mixture, the second - for the timeliness of the release of combustion products. In this design, there is no head, which in most cases is located on the cylinder block. TO the benefits of OROC engines refers to the fact that the pistons "work on one crankshaft." This is what makes it possible to create these engines of small size and weight. This leads to a wider scope of their application. Also, this engine works equally well on both diesel and gasoline. With all this, the pistons travel much less distance, and therefore the friction force is several times less, which prolongs the life of the engine. And also, given that it has a smaller size and weight, therefore, two times fewer parts are required for its manufacture. This saves money. Common Lack of ODA engines is that they were not so long ago developed and are being improved to this day. Because of this, unforeseen problems should not be ruled out during its operation;

   
   OROS is a boxer engine. Photo

3. ... The boxer engine is also designed to operate large military equipment. In this case, the pistons divide one cylinder and move in the same direction, but each has its own crankshaft. The combustion chamber is created at that moment of the minimum distance between the pistons. The similarity with OROC is that air enters the cylinders themselves, and excess gases are removed by turbocharging. This power plant has a capacity of 700 horsepower, the maximum number of revolutions is 2000. The volume is equal to six or thirteen liters.

   
   Tank boxer engine. Photo

Pros of boxer engines

Regardless of the type of motor, boxer engines have common advantages, among which are:

Cons of boxer engines

Of course, there is nothing perfect in the world, which can be said about boxer engines. The disadvantages include:

• A very large amount for service that requires the intervention of professionals;
• High cost of spare parts;
• The complexity of the entire structure as a whole;
• Higher oil consumption during operation.

But even taking into account the above disadvantages, this does not prevent many manufacturers from installing boxer engines on their cars. Before that, all the pros and cons are weighed.

Chief among the pluses is more opportunities and broader perspectives. After all, in fact, all the shortcomings run into money. However, most people are aware of the fact that more money is required for good quality. In addition, the use of boxer engines is the next step in technological development.

Differences between a boxer and in-line four-cylinder engine

Now we are going to talk about the general features and distinctive features of the Boxer Four and Straight Four in-line and boxer four-cylinder engines. And also about their pros and cons. Below is a short video where everything is described in detail.

Differences between a boxer and in-line four-cylinder engine. Video

1. Both designs operate on the principle of a four-stroke cycle - start, compression, stroke and release.
2. In both designs, a working stroke occurs every 180 degrees of rotation of the number of shafts, but they have a slightly different ignition order.
3. On each engine we see cylinders numbered 1, 2, 3, 4. For the opposite ones, the ignition order is 1, 3, 2, 4., and for the inline 1, 3, 4, 2. So the order of operation of the last two cylinders is changed ... This difference affects how the engine is balanced. On a boxer engine, the cylinder pairs, outward and inward, move together. This means that the first-order inertial force that occurs when the piston reaches top or bottom dead center cancels out. It's the same story with an in-line four-stroke engine - the first order inertia forces cancel each other out, as for the second order inertia force - here the engines start to differ. Second-order inertia forces are created due to the fact that the piston moves faster at the top of the cylinder than at the bottom. When the piston reaches its maximum or minimum dead center, the second order inertial forces are directed upward or downward from the piston. In a boxer engine, because the pistons are opposite each other, these inertial forces are balanced to ensure smooth engine operation. In an in-line four-cylinder setup, all forces are directed in one direction, which causes the engine to vibrate if the balance shafts are not used.

But still, the boxer engine is not ideal, due to the fact that the pistons are not in line with each other, torque is created, which contributes to the rotation of the engine along the vertical axis.

BTW SPEAKING! If you add two cylinders to any of the designs, be it a boxer or in-line six, all the inertial forces of the torque will be compensated.

You might have thought that a boxer six would have vibrations due to a group of 3 pistons, but each group of three pistons balances the vibration of the other group. If we compare the dimensions of the engines Subaru EJ20 2.0L Boxer-4 and Toyota 22R-E 2.0L Inline-4, then they are almost the same, with this configuration, the engines usually do not have a volume of more than three liters, but before they were produced much larger volume.

The largest modern inline-four is a 2.7-liter Toyota Tacoma gasoline engine.

But this does not mean that the inline four does not have its own advantages:

1. It is generally more compact, has only one cylinder head and is not as wide. This leaves more room for suspension and allows for a smaller turning radius as the car's tires have more room to turn.
2. In terms of gas distribution, this particular inline-4 has a single overhead camshaft, but more often there are two camshafts in modern cars.
3. The big advantage of an inline-four is that it has only one cylinder head, one intake and one exhaust camshaft, fewer moving parts, less weight, and it's much easier to reach the cylinder block for maintenance, whether it's adjusting valves or replacing plugs with inline configuration is much easier to do.

Finally we got to the topic of engine sound. Many people claim that boxer engines sound better, but this is not really an advantage. This sound is due to the different lengths of the tailpipes.

And since Subaru has ditched this exhaust design, the new boxer fours will sound just like the rest of the four-cylinder engines. It is of course possible to create an exhaust system with tailpipes that are of different lengths to obtain a unique exhaust sound. But this can worsen the purging of the cylinder due to unequal pulsations, and there is no particular sense in this. However, when it comes to a boxer engine, fitting different lengths of pipes seems attractive.

Difficulties in the repair and maintenance of boxer engines

As mentioned earlier, if you need to carry out any manipulations on the engine, you cannot do without the help of a specialist. In opposition engines, without consequences, it will only be possible to change the oil with your own hands.

One of the factors that has a significant impact on the service life is the timely and systematic de-coking process. This procedure cleans the combustion chamber, valves and pistons from accumulated carbon deposits. It is best to carry out this procedure in the fall or early spring. It is during this period that it will be reasonable to check the oil with its changeable.

A power unit such as a boxer engine (in particular, the manufacturer Subaru) is similar in principle to a standard, in-line internal combustion engine. It is distinguished by the specificity of the arrangement of pistons, cylinders, due to the horizontal (and not the usual vertical) installation of the engine. Therefore, the pistons of the boxer engine are located horizontally, moreover, opposite (opposite) to each other, in pairs. Also, each of these pairs of engine pistons has a pair of camshafts.

At first glance, Subaru's boxer engine is more compact than others, with the same power and volume. Such an illusion is created because it is “flat” and evenly fills the engine compartment. At the same time, the motor-plate is short, flat, but wide. Its design is represented by half-blocks of two cylinders, but in width, apart from a crankcase with a pallet, like an in-line one, there is also a half-block and a head.

Subaru's boxer internal combustion engines were first noticed and installed in sports cars by racers. 12-cylinder engines were later developed for them, instead of the 6-cylinder ones used.

Pros of the Subaru boxer engine

The Subaru boxer engine has many advantages:

1. The distribution of mass is symmetrical about the axle, not specifically on it (less load on the rear wheels) - due to the low center of gravity (plus the possibility of its displacement).
2. High functionality, a relatively long duration of work until the first need for repair is the most important plus and reason for installing a Subaru boxer engine.
3. Minimization (or complete absence of vibration), which, when installing a conventional engine, creates considerable discomfort for the driver / passenger.

The first plus (dignity) is most appreciated by the owners of sports cars. Because, at high-speed corners, the Subaru boxer engine will give more resilience... In addition, the speed indicators of cars using these particular engines are comparatively better than similar ones (especially among 12-cylinder ones).

The second advantage is durability of the engine- checked / confirmed numerous times. Before the need for overhaul, the boxer engine will delight the car owner with more than one thousand kilometers without problems.

The last (third advantage) is possible, among other things, due to the horizontal arrangement of the pistons, working from each other, creating a kind of balance, counterweight... Unfortunately, not all Subaru boxer engine models boast maximum vibration resistance. The best way to "withstand" vibration loads is a six-cylinder boxer engine (similar to a 6-cylinder variation of an in-line engine). But already the 4-cylinder does not possess such successes and significant advantages.

Cons of a Subaru boxer engine

However, in every advantage of the Subaru boxer engine, you can find a small "fly in the ointment". Of these disadvantages:

1. The high cost of engine maintenance, the difficulty in selecting the necessary spare parts. And, among other things, it is advisable to trust only professionals who specialize in this in matters of repairing specifically such engines.
2. The high cost of the actual boxer engine made by the manufacturer Subaru, explained by the complexity of the design.
3. Also, a large oil consumption is added to the consumable items using such an engine.

Independent repair of the boxer engine is also impossible due to the need for a specialized tool, without which many parts of the non-standard, horizontally located engine cannot be reached.

The range of uses for the Subaru boxer engine

The slightly difficult financial situation of a significant mass of motorists does not allow the popularity of Subaru's boxer engines to spread. Their application is most widespread in the field of racing, high-speed car models. Because here, the previously mentioned advantages of Subaru boxer engines are much more important and cover the disadvantages of their use.

In addition, they are installed, of course, in the models of cars of the manufacturer Subaru. Also, Porsche often resorts to installing these particular engines in their cars.

A boxer engine is a modified unit with a structure different from a conventional in-line engine. Its pistons are at a rotated angle, so the vapors move towards and back. The adjacent pair, located along the axis of the plane of the motor, moves identically, but with a small time interval, providing the engine's stroke. The movement of the pistons inside the engine remotely resembles a boxing match, therefore this type of internal combustion engine is called a boxer.

Operating principle

Based on the design of the unit, each piston is installed on the one intended for it. The number of cylinders is necessarily even, it ranges from 2 to 12. The most common engines for cars are motors with four and six cylinders.

In general, the principle of operation of this type of unit is similar to a conventional in-line motor. The difference lies in the fact that the pistons in it move horizontally, and not up and down, which is due to the horizontal arrangement of the cylinders. These types of motors are characterized by the presence of two cylinder heads located horizontally on both sides.

Motor applicability

Quite a lot of car models with a boxer engine under the hood drive on the roads. But there are only two leading companies that are engaged in the implementation and development of these units, namely Porsche. Although earlier these units were installed on such car brands as Honda, Ferrari, Chevrolet, Alfa Romeo and many others.

One of the classic flat-engine cars - Alfa Romeo 33

Models from the Porsche manufacturer, such as the Cayman and 911, are powered by six-cylinder engines, while the sportier variants are equipped with eight- and even twelve-cylinder forced engines.

Most experienced car owners say that two- and four-cylinder boxer engines are virtually indistinguishable from their in-line counterparts, but the more cylinders, the more pronounced the difference.

A bit of history

The first serial diesel boxer engine was a motor produced by Subaru in 2008. It was a four-cylinder unit with a volume of 2 liters and a capacity of 150 horses. This engine received a fuel supply control system.

In Soviet times, tanks were equipped with one of the types of modern boxer engine, which has a similar principle of operation, but completely opposite to it in design. It contained 2 pistons per cylinder, which worked, moving towards each other. At the moment when the distance between the pistons was minimal, fuel entered the resulting combustion chamber between them. That is, if a modern engine has one crankshaft and 2 block heads, with piston stroke from each other, then the Soviet 5TDF had 2 crankshafts and 1 head with pistons moving towards each other. Also a feature is the two-stroke operation of this unit and its versatility in terms of the fuel used. Initially, it was a diesel type of engine, but it could successfully run on gasoline, kerosene, aviation fuel, even fuel oil. On the latter, however, not very long. This versatility was due to the presence of a fairly high compression ratio in the cylinders.

After the production of T-64 tanks was discontinued, the engine was abandoned in favor of V-shaped configurations, considering the boxer engine resource-intensive and not convenient enough for further use.

The very idea of ​​developing a boxer engine is not a merit of Subaru, as many think. Such units were installed on Ikarus buses, on a fairly large number of motorcycles (starting with domestic Dnieper and Urals, ending with BMW R1200GS, as well as similar ones). Naturally, like any development, the boxer engine has its pros and cons.

Pros of a boxer motor

The main advantages include the following qualities:

• Due to the design, the center of gravity is shifted down. This greatly improves the handling of the vehicle, especially at high speeds. Although we do not have such roads where it could be verified without risk.
• No vibration when working. This only applies to motors with 6 or more cylinders. In engines with two or four cylinders, secondary vibrations are not much lower than in conventional in-line engines.
• Enough . It is believed that boxer engines have a resource of over a million kilometers.

Cons of the motor

Naturally, units of such a design have rather serious drawbacks, which the developers have not yet gotten rid of.

• The maintenance cost is substantially higher than that of conventional motors. In addition, the opposed one is problematic, and sometimes almost impossible to repair yourself. It has a rather complex structure, so it is better to have it repaired by professionals. And this will cost a lot of money.
• Due to the first drawback, the second one flows out smoothly. In small towns, you may simply not find a sufficiently qualified master who is guaranteed to provide service with proper quality.
• The complexity of the design, as well as the greater number of elements, increases the cost of its spare parts several times, as well as their number.
• High for a boxer engine is considered the norm. Moreover, it is so high that, with a similar flow rate, an ordinary unit must necessarily undergo overhaul. This leads to the situation when, unknowingly, the motorist simply did not control the oil level in the engine, which led to oil starvation. Given the horizontal arrangement of the piston, this can quickly lead to irreversible consequences.

Having familiarized yourself with how the boxer engine works, we can conclude that almost all the disadvantages of this type of engine can be attributed to the financial part, but for many car owners this is a rather serious factor taken into account when buying a car.

Representatives of the Subaru company believe that returning to standard types of engines would be a huge step back for them, so they are not going to change boxer engines for other models. According to them, the level of sales is not affected either by the price of service or by the price of the cars themselves.

Boxer engines have been designed to save space under the hood. As a result, the unit is lower, shorter, but much wider. That is, from the vertical plane it was transferred to the horizontal one. That is, in fact, nothing has changed, except for the increased price, as well as the complexity of service. And as for the forced models with one or more turbines, their service life ranges from hundreds of thousands of kilometers to several hundred, not a million. The same applies to fuel consumption - it is about a third higher than that of a standard engine of the same power.

Considering all the advantages and disadvantages of this type of engine, it is difficult to call them any technical breakthrough in terms of the automotive industry, but these engines also have their fans. Do you agree with us?

After the creation of the first ICE, questions arose almost immediately about its improvement and increase in power. The first engine was single-cylinder, and the simplest solution immediately suggested itself, allowing to increase its power - to increase the number of cylinders. But the next steps in the development of the internal combustion engine were not so obvious, since these several cylinders can be arranged in different ways - vertically in a row one after another, at an angle or horizontally. This last version was called the boxer engine, i.e. an engine, the cylinders of which are located horizontally, opposite (opposite) each other.

Boxer engine options

However, even such a simple technical solution - placing the engine cylinders horizontally opposite each other - can be implemented in several ways. When such a boxer engine is running, its pistons can move in different ways.

Boxer boxer

During the operation of such a motor, the pistons are always at a distance from each other, and each works in its own cylinder - if one is located at the maximum distance from the engine axis, then the other, adjacent, occupies a similar position.

This way of working resembles the movement of a boxer, which is why it is called "boxer". Very often uses similar boxer engines Subaru. The described engine is shown in the photo below.

OPOC, reviving old ideas

Another construction principle implements an opposed engine of the OPOC type. Today they are beginning to develop again thanks to the investments of the notorious Bill Gates. The device of such a motor is shown in the figure below.


This boxer engine is a two-stroke engine. The figure clearly shows that there are two pistons in the cylinder, and they are fixed on one crankshaft (in the figure they are designated as red and blue). Red provides an inlet for the mixture, and blue provides an outlet for combustion products. From the design of such a boxer engine, the cylinder head and valve drive mechanism disappeared. In addition, the advantage of such a boxer is that the pistons work on one crankshaft.

All this significantly reduced the weight of the boxer engine and significantly expanded the scope of its use. Another feature is that it can be either diesel or gasoline. It is imperative to clarify that, like any two-stroke engine, it needs to be purged from the cylinders. For this, an electric motor powered from an external source is used. When the boxer engine is on mode, the electric motor is shut off and the air supply is converted to a turbocharger.

Considering the design of such a boxer engine, it is necessary to note its advantages: an increase in efficiency, provided by the fact that the expanding gases press on two pistons, and not on the wall of the combustion chamber, as well as an increased force on the shaft. In addition, each piston travels a shorter distance, which reduces frictional force and therefore losses.

Considering other advantages that a similar boxer engine promises, it is worth noting - the manufacturer reports that when it is used as a diesel engine, then:

• such an engine is fifty to thirty percent lighter than a conventional turbodiesel;
• such a power unit contains fifty percent fewer parts than a conventional diesel engine;
• takes fifty to forty five percent less space under the hood;
• more economical by fifty to forty five percent.

However, it should be borne in mind that such an opposed power unit is still quite crude, which means that the noted advantages reflect to a greater extent the expectations of its developers.

Boxer tank engine

Yes, there was such an engine, this is the 5TDF, developed for the T-64 tanks, as well as the subsequent T-72 and others. Then he provided the necessary power for the given dimensions. A similar boxer engine and its structure are shown in the figure below.

As can be seen from the figure, its pistons are located in one cylinder and move in the opposite direction, but each work on its own crankshaft. With a minimum distance between the pistons, a combustion chamber is formed between them, where the fuel is ignited. There is a boxer engine, both gasoline and diesel. By analogy with OPOC, turbocharging is used to supply air to the cylinders, as well as to remove the exhaust gases.

The principle of counter movement of pistons used made it possible to simplify the design, ensure the power and compactness of the power plant. So, a similar diesel boxer power unit at two thousand revolutions, a volume of thirteen and six tenths of a liter gave out seven hundred horsepower, while taking up a minimum of space.

What's good and bad about oppositor?

It should be noted that in the history of the car, many manufacturers at various times have used the boxer engine, trying to realize the advantages provided to it. However, at the moment, SUBARU uses such motors more often than others on their cars.


It should be noted right away that it is the device of the opposed power unit that provides its advantages when installed on a car:

• low center of gravity of the car, which gives it additional stability when driving;
• reduction of both noise and vibration due to the movement of the pistons towards the opposite, due to which the boxer engine is considered quieter than similar in-line engines;
• a significant resource reaching a million kilometers with proper operation.

However, everything is not always good, there are also disadvantages and disadvantages of the opposed one. Of these, it is worth noting:

1. repair of such a motor is very difficult;
2. the engine device is also quite complex, and, accordingly, it has a high price;
3. maintenance costs are high, and the service itself is extremely costly and inconvenient, requires highly qualified performers;
4. increased oil consumption during operation.

Despite the noted disadvantages and disadvantages, a number of cars (the already mentioned SUBARU and some Porshe models) are equipped with opposed power units. One must think that manufacturers accurately weigh their advantages and disadvantages and consciously go for the use of such a motor.

For an internal combustion engine, the arrangement of the cylinders horizontally is only one of the possible construction options, but nevertheless, in this case, the resulting boxer engine is distinguished by great capabilities and significant prospects for use in a car.

I continue to talk about internal combustion engines. Moreover, I like to talk about engines that are not understandable for a common man in the street, for example, from Volkswagen. Today, no less interesting engine, which is also installed on a narrow range of cars. It's about a boxer engine. Basically, now such units are used by Subaru, as well as the Volkswagen Group corporation, in their cars. So what kind of engine is this? Read on ...

- an internal combustion engine, in which the pistons are horizontal (or at an angle of 180 degrees), in contrast to an in-line internal combustion engine, in which the pistons are vertical. That is, in simple words, it can be called a horizontal motor. The pistons of such a unit are located - two on the right and two on the left. During operation, the pistons converge and diverge horizontally. Since the pistons are separated, each group of pistons has (two on the right and two on the left), two camshafts. That is, there are two camshafts on the right - 8 valves and the same ones on the left. Gas distribution mechanisms in a boxer engine (camshafts and valves) are located vertically, in contrast to a classic in-line engine, where they are located horizontally. Here's a small diagram.

The first boxer engines appeared in 1938, they were installed on Volkswagen Käfer cars (Volkswagen Beetle was used in chic application). It was Volkswagen who first developed the horizontally opposed engine. Some modern cars belonging to the Volkswagen Group are now equipped with such engines (for example, Porsche 997, Porsche Boxster, etc.). Also in the 1940s, SUBARU was independently developing its engine. And to this day, Subaru equips its cars with horizontal boxer engines.

Why was the boxer engine created?

Was designed to lower the vehicle's center of gravity. Probably everyone knows that the lower the center of gravity, the better the driving characteristics of the car, the roll of the car will be less when cornering.

Advantages of a boxer engine

1) As I wrote above, it was created to lower the center of gravity of the car, which has a very good effect on driving characteristics.

2) Another plus is the arrangement of the cylinders. When moving towards each other in a horizontal plane, extraneous vibrations are much more attenuated. Therefore, this engine is considered to be much quieter than its in-line or V-shaped counterparts.

3) Also from the pros, I would like to note the large resource of this type of engine. For example, SUBARU engines have a service life of about 1,000,000 kilometers, with proper use and timely replacement of consumables.

Cons of a boxer engine

1) The first and most significant disadvantage is the difficult repair of such an engine.

2) The complex structure, which means the expensive price of this engine.

3) Complicated maintenance.

This unit is durable, but complex in structure. Its dynamic performance is similar to that of an in-line gasoline engine. Power and consumption. And now a short video.

SUBARU boxer engine video

Let me finish with this, I think it became a little clear what it is and how it works.