The principle of operation of a 4-stroke engine. What is the difference between a two-stroke engine and a four-stroke

The principle of operation of a four-stroke internal combustion engine (ICE). Operating cycle of a 4-stroke engine.

In this article, you will learn how a four-stroke internal combustion engine works. The main part of the power products presented on the MotoSvit website works specifically with four-stroke engines (motor pumps, general-purpose engines, snow blowers, and even unique ones with four-stroke engines that operate in any plane, etc.). If this article is useful for you, do not be lazy and share with your friends, the buttons at the end of the article.

Glad to see you friends on the site.
Very often, MotorSvit customers ask a question when choosing a boat motor:

What is better to choose a boat motor two-stroke or four-stroke engine?

In order to answer this question, we recommend that you find out and see the working cycle of a four-stroke engine.

Let's not delay, let's get down to business i.e. to this process. We tried to give you the information as simply as possible and without unnecessary complicated technical terms + visual pictures will help you quickly understand and understand the principle of operation of a four-stroke engine.

By the way, now we are considering with you a piston four-stroke gasoline internal combustion engine. You can read the internal combustion engine, its types and definition.

As the name implies, a four-stroke engine's work cycle consists of four main stages - strokes (as shown in the picture above). This is the main difference between a 4-stroke engine and. And now consider each cycle (cycle) of the internal combustion engine.

During this stroke, the piston moves from top dead center (TDC) to bottom dead center (BDC). In this case, the camshaft cams open the intake valve, and through this valve a fresh fuel-air mixture is sucked into the cylinder.

The piston goes from bottom dead center to TDC, compressing the mixture. This significantly increases the temperature of the mixture. The ratio of the working volume of the cylinder at BDC and the volume of the combustion chamber at TDC is called the compression ratio.

The compression ratio is a very important parameter, usually the higher it is, the greater the fuel efficiency of the engine. However, a higher compression engine requires higher octane fuel, which is more expensive.

Shortly before the end of the compression cycle, the air-fuel mixture is ignited by a spark from a spark plug. During the journey of the piston from TDC to BDC, the fuel burns out, and under the influence of the heat of the burnt fuel, the working mixture expands, pushing the piston.

The degree of “underturning” of the engine crankshaft to TDC when the mixture is ignited is called the ignition timing.

The ignition advance is necessary so that the gas pressure reaches its maximum value when the piston is at TDC. In this case, the use of the energy of the burnt fuel will be maximum. Fuel combustion takes almost a fixed time, so to increase the efficiency of the engine, you need to increase the ignition timing with increasing speed.

In older engines, this adjustment was made by a mechanical device (centrifugal and vacuum regulator acting on the chopper). In more modern engines, electronics are used to adjust the ignition timing.

After the BDC of the operating cycle, the exhaust valve opens, and the upward moving piston displaces the exhaust gases from the engine cylinder. When the piston reaches TDC, the exhaust valve closes and the cycle starts over.

It is also worth remembering that the next process (for example, intake) does not have to begin at the moment when the previous one (for example, exhaust) ends. This position, when both valves (inlet and outlet) are open at once, is called valve overlap. Valve overlap is necessary for better filling of the cylinders with a combustible mixture, as well as for better cleaning of the cylinders from exhaust gases.

For clarity, below you can see animated pictures of the working cycle of a four-stroke gasoline engine.

When buying a new scooter, people often ask questions like " Which is better 2 stroke or 4 stroke". There is no single answer to this question. Each motorist will find both disadvantages and advantages in both types of engines. To figure it out for yourself which scooter is better 2 stroke or 4 stroke, you should first find out What is the difference between 2 stroke and 4 stroke engine.

The difference between a two-stroke and a four-stroke

Main differences between two-stroke and four-stroke engines is due to the difference in their gas exchange devices - the supply of a fuel-air mixture to the cylinder and the removal of exhaust gases. IN 4t engine the processes of cleaning and filling the cylinder are carried out using a special gas distribution mechanism (GRM), which closes and opens the intake and exhaust valves at a specific time in the working cycle. IN engine 2t filling and cleaning of the cylinder are carried out in parallel with the compression and expansion strokes - at a time when the piston is located near BDC (bottom dead center). To do this, there are two holes in the walls of the cylinder - inlet (purge) and outlet, through which the fuel mixture is supplied and the exhaust gases are released. The two-stroke engine does not have a valve timing mechanism, which makes it much lighter and simpler.

Which engine is more powerful 2 stroke or 4 stroke

Unlike a 4 ton engine, in which one stroke occurs for two revolutions of the crankshaft, in a 2 ton engine, a stroke occurs with each revolution of the crankshaft. This means that a two-stroke engine must have (in theory) twice as much liter capacity (the ratio of power to engine volume) as a four-stroke. But in practice, the predominance is only 1.5 - 1.8 times. This happens due to inadequate use of the piston stroke during expansion, the worst mechanism for ridding the cylinder of exhaust gases, the cost of a share of power for scavenging and other phenomena associated with the distinctive features of gas exchange in 2-stroke engines.

Fuel consumption 2t and 4t

Surpassing the four-stroke engine in liter and power density, two stroke engine inferior to him in economy. The expulsion of exhaust gases is carried out in it by a fuel-air mixture arriving in the cylinder from the crank chamber. In this case, part of the fuel mixture ends up in the exhaust channels, being removed together with the exhaust gases and not producing useful work.

Grease 4 t and 2 t

Two-stroke and four-stroke engines have a different design and principle of operation of the engine lubrication system. In 2-stroke scooters, it is carried out by mixing engine oil with fuel in established proportions (usually 1:25 ... 1:50). The fuel-air-oil mixture, circulating in the crank and piston chambers, lubricates the connecting rod and crankshaft bearings, as well as the cylinder mirror. When the fuel mixture ignites, the oil burns together with gasoline. The products of its combustion are removed together with the exhaust gases.

There are 2 methods of mixing oil with gasoline. Conventional mixing before pouring fuel into the tank and a separate supply, in which the fuel-oil mixture is formed in the inlet pipe located between the carburetor and the cylinder.

Separate lubrication system for two-stroke engine

1. oil tank
2. carburetor
3. throttle cable separator
4. throttle stick
5. oil control cable
6. plunger dosing pump
7. oil inlet hose

All modern 2t scooters use separate oil supply(we fill in 2t oil separately from gasoline). IN two stroke scooter the engine has an oil tank, the pipeline of which is connected to an oil pump that supplies oil to the inlet pipe in the amount that is necessary depending on the amount of air-gasoline mixture. The productivity of the pump depends on the position of the "gas" knob. The more fuel is supplied, the more oil is supplied, and vice versa. A separate lubrication system for two-stroke engines is considered more flawless. With it, the ratio of oil to gasoline at light loads can reach 1:200, which leads to a reduction in smoke, a decrease in carbon deposits and oil consumption. This design is used on modern scooters with two-stroke engines.

In a four stroke engine oil does not mix with fuel and served separately. To do this, the engines are equipped with a traditional lubrication system consisting of an oil pump, filter, valves, pipelines. The role of the oil tank can be performed by the engine crankcase (wet sump lubrication system) or a separate tank (dry sump system).

Lubrication system of a four-stroke engine with a wet and dry sump

1. sump
2. oil intake
3. oil pump
4. oil filter
5. safety valve

When lubricating with a “wet” crankcase, pump 3 takes oil from the sump, pumps it into the outlet cavity and then delivers it through the channels to the crankshaft bearings, crankshaft and timing parts. When lubricating with a “dry” sump, oil is poured into the tank, from where it is pumped to the rubbing planes. That part of the oil that flows into the crankcase is pumped out by an auxiliary pump, which gives it back to the reservoir. There is a filter to clean the oil from wear products of engine parts. If necessary, a cooling radiator is also installed, since during operation the oil temperature can rise to high temperatures.

What is the difference between 2-stroke oil and 4-stroke oil?

Since oil burns in 2t engines, but not in 4t engines, the requirements for its properties vary greatly. Oil used in 2-stroke engines must leave a minimum amount of carbon deposits in the form of ash and soot, while oil for 4t engines must guarantee stable performance for as long as possible.

When choosing power equipment, special attention must be paid to the type of engine. There are two types of internal combustion engines: 2-stroke and 4-stroke.

The principle of operation of an internal combustion engine is based on the use of such properties of gases as expansion when heated, which is carried out due to the forced ignition of a combustible mixture injected into the air space of the cylinder.

You can often hear that a 4-stroke engine is better, but to understand why, you need to take a closer look at the principles of operation of each.

The main parts of an internal combustion engine, regardless of its type, are the crank and gas distribution mechanisms, as well as systems responsible for cooling, power, ignition and lubrication of parts.

The transfer of the useful work of the expanding gas is carried out through a crank mechanism, and the gas distribution mechanism is responsible for the timely injection of the fuel mixture into the cylinder.

Four-stroke engines - Honda's choice

Four-stroke engines are economical, while their operation is accompanied by a lower noise level, and the exhaust does not contain a combustible mixture and is much more environmentally friendly than a two-stroke engine. That is why Honda uses only four-stroke engines in the manufacture of power equipment. Honda has been introducing its four-stroke engines to the power market for many years and has achieved the highest results, while their quality and reliability have never been questioned. But still, let's look at the principle of operation of 2 and 4 stroke engines.

The principle of operation of a two-stroke engine

The duty cycle of a 2-stroke engine consists of two stages: compression and power stroke.

Compression. The main piston positions are top dead center (TDC) and bottom dead center (BDC). Moving from BDC to TDC, the piston alternately closes first the purge and then the exhaust port, after which the gas in the cylinder begins to compress. At the same time, a fresh combustible mixture enters the crank chamber through the inlet window, which will be used in subsequent compression.

working stroke. After the combustible mixture is compressed as much as possible, it is ignited by an electric spark generated by a candle. At the same time, the temperature of the gas mixture rises sharply and the volume of the gas grows rapidly, exerting a pressure at which the piston begins to move towards the BDC. As the piston descends, it opens the exhaust port, while the combustion products of the combustible mixture are released into the atmosphere. Further movement of the piston compresses the fresh combustible mixture and opens the purge hole through which the combustible mixture enters the combustion chamber.

The main disadvantage of a two-stroke engine is the high fuel consumption, and some of the fuel does not have time to benefit. This is due to the presence of a moment at which the purge and outlet openings are simultaneously open, which leads to a partial release of the combustible mixture into the atmosphere. There is also a constant oil consumption, since 2-stroke engines run on a mixture of gasoline and oil. Another inconvenience is the need to constantly prepare the fuel mixture. The main advantages of a two-stroke engine remain its smaller size and weight compared to a 4-stroke counterpart, but the size of power equipment allows you to use 4-stroke engines on them and experience much less hassle during operation. So the lot of 2-stroke engines is left to various modeling, in particular, aircraft modeling, where even an extra 100g matters.

The principle of operation of a four-stroke engine

The operation of a four-stroke engine is significantly different from that of a two-stroke engine. The working cycle of a four-stroke engine consists of four stages: intake, compression, power stroke and exhaust, which is made possible by the use of a valve system.

During the entry stage the piston moves down, the inlet valve opens, and a combustible mixture enters the cylinder cavity, which, when mixed with the remnants of the used mixture, forms a working mixture.

When compressed the piston moves from BDC to TDC, both valves are closed. The higher the piston rises, the higher the pressure and temperature of the working mixture.

working stroke A four-stroke engine is a forced movement of the piston from TDC to BDC due to the action of a sharply expanding working mixture, ignited by a spark from a candle. As soon as the piston reaches BDC, the exhaust valve opens.

During graduation The combustion products displaced by the piston moving from BDC to TDC are released into the atmosphere through the exhaust valve.

Due to the use of a valve system, four-stroke internal combustion engines are more economical and environmentally friendly - after all, the emission of unused fuel mixture is eliminated. In operation, they are much quieter than 2-stroke counterparts, and much easier to operate, because they work on a regular AI-92, which you fill your car with. There is no need for constant preparation of a mixture of oil and gasoline, because the oil in these engines is poured separately into the oil sump, which significantly reduces its consumption. That is why Honda only produces 4-stroke engines and has achieved tremendous success in their production.

The four-stroke engine is a reciprocating internal combustion engine. The working process of all cylinders in these units takes 2 crankshaft circuits or four piston strokes. Since the middle of the twentieth century, a 4-stroke engine has been the most common type of piston engine.

Working principle and main characteristic

The working cycle of an internal combustion engine (ICE) consists of a series of processes in which the power of the engine acting on the crankshaft is increased. The working cycle consists of several stages:

• the cylinder is filled with fuel mixture;
• the mixture is compressed;
• the fuel mixture ignites;
• gases expand and the cylinder is cleaned.

In an internal combustion engine, the piston moves in one direction (up or down). The crankshaft makes one revolution in two cycles. The working stroke of the piston is the one at which useful work is done and the burnt gases expand.

Two-stroke engines are called engines in which the cycle is completed in one revolution of the crankshaft or in two cycles. Four-stroke units are characterized by the completion of the working cycle for two turns of the crankshaft or for four bars.

The main characteristic indicators of a 4-stroke engine:

1. Due to the movement of the working piston, the exchange of gases occurs.
2. The unit is equipped with a gas distribution mechanism, allowing the cylinder cavity to switch to intake and exhaust.
3. going on gas exchange during a single half-turn of the crankshaft.
4. Gear reducers and a belt chain drive make it possible to change the moments of gasoline injection, ignition and timing gear drive in relation to the crankshaft speed.

Story

Approximately in 1854-1857 the Italians Felicce Matoczi and Eugene Barsanti created a device that, according to information available today, was similar to four stroke motor. The invention of the Italians was lost and only in 1861. Alfon de Rocher patented this type of engine.

For the first time, a workable four-stroke engine was created German engineer Nikolaus Otto. The four-stroke Otto cycle was named after him, and a 4-stroke engine using spark plugs is called an Otto engine.

Features of the 4-stroke engine

In a two-stroke engine, lubrication of piston and cylinder pins, crankshaft, piston, bearing and compressor rings is carried out by pouring oil into gasoline. The crankshaft of a 4-stroke engine is located in an oil bath, which is a significant difference. That is why there is no need to mix fuel and add oil. All that needs to be done by the owner of the car is to fill the fuel tank with gasoline.

Thus, the car owner does not need to purchase special oil, without which a two-stroke engine cannot function. In addition, in the presence of a four-stroke engine on the piston mirror and on the walls of the muffler, the amount of carbon deposits is reduced. Another important difference is that in a two-stroke engine, a combustible mixture splashes into the exhaust pipe, which is due to its design.

Admittedly, four-stroke engines also have some minor drawbacks. For example, their working moments for regulating the thermal valve clearance are not of particularly high quality.

Unit design

Camshaft four-stroke engine located in the cylinder head. It is driven by a drive wheel mounted in the crankshaft. The camshaft opens and closes one of the valves: exhaust or intake, depending on the location of the piston. Cams are also located on the camshaft, which actuate the rocker arms.

Rocker arms after triggering, they begin to act on a specific valve and open it. It is important that there must be a thermal gap (narrow gap) between the adjusting screw and the valve. When heated, the metal expands, so if the gap is too small or not at all, valves cannot completely close the exhaust and intake channels.

At inlet valve clearance should be less than that of the exhaust valve because the exhaust gases are hotter than the mixture. Accordingly, the intake valve heats up less than the exhaust valves.

Engine operation

As already noted, the operation of a four-stroke engine consists of four piston strokes or two revolutions of the crankshaft.

Stages of work:

1. Inlet. The piston moves down, opening the intake valve. From the carburetor, the combustible mixture enters the cylinder. When the piston reaches the bottom position, the intake valve closes.
2. Compression. The piston moves up, causing the combustion of the combustible mixture. As it approaches the top point, the compressed gasoline ignites.
3. Extension. Gasoline ignites and burns. As a result, the combustible gases are stretched, and the piston moves down. In this case, two valves are closed.
4. Release. The crankshaft by inertia continues to move around its axis, and the piston moves up. At the same time, the exhaust valve opens, and the exhaust gases enter the pipe. When the valve passes the dead point, the intake valve closes.

Design and operational differences of four-stroke two-stroke gasoline engines

The main difference between a four-stroke engine and a two-stroke due to different mechanisms of gas exchange, namely: the removal of exhaust gases and the supply of a fuel-air mixture to the cylinder.

Cylinder filling processes and its cleaning in a four-stroke engine occurs with the help of a special gas distribution mechanism, which opens and closes the working cycle at a certain time.

Cylinder cleaning and its filling in a two-stroke engine is performed at the same time with expansion and contraction when the piston is near the bottom dead center. There are two holes in the walls of the cylinder for this: purge or inlet and outlet. The fuel mixture enters through the exhaust port and the exhaust gases exit.

The main differences between two-stroke and four-stroke engines:

1. liter power. In a four-stroke engine, there is one stroke for every two revolutions of the crankshaft. Therefore, theoretically, a two-stroke engine should have twice the liter capacity of a four-stroke. But in practice, the excess is about 1.8 times, due to the use of a piston when expanding the stroke, as well as the presence of a worse mechanism for releasing the cylinder from exhaust gases and high costs for blowing off part of the power.
2. Fuel consumption. A two-stroke engine is superior to a four-stroke engine in specific and liter power, but inferior in efficiency. The exhaust gases are displaced by the air-fuel mixture, which enters the cylinder from the connecting rod-crank chamber. Part of the fuel mixture enters the exhaust channels and is removed with the exhaust gases.
3. For two-stroke and four-stroke engines, the principle of engine lubrication is significantly different. Two-stroke models are characterized by the need to mix gasoline with engine oil in certain proportions. An oil-air-fuel mixture circulates in the piston and crank chambers, lubricating the crankshaft and connecting rod bearings. When the fuel mixture ignites, the smallest drops of oil burn together with gasoline. Combustion products leave together with the fulfilled gases.

Gasoline is mixed with oil in two ways. This can be a simple mixing, which is carried out before pouring fuel into the tank and a separate transmission. In the second case, the oil-fuel mixture is formed in the inlet pipe located between the cylinder and the carburetor.

The engine in the latter case is equipped with an oil tank with a pipeline connected to a plunger pump. The pump delivers oil to the inlet in the amount that is needed. The performance of the pump depends on how the “gas” supply handle is located. The flow of oil is greater, the more fuel is supplied. More perfect is a separate lubrication system for a two-stroke engine. The ratio of gasoline to oil with it can reach 200:1. This results in lower oil consumption and less smoke. Such a system is used, for example, on modern scooters.

In four-stroke engines, gasoline and oil are not mixed, but served separately, for which the engines have a classic lubrication system, which consists of a filter, an oil pump, a pipeline and valves. The engine crankcase (lubrication with a “wet” crankcase) or a separate tank (“dry” crankcase) can act as an oil tank.

In the first case, the pump sucks oil from the sump, directs it to the inlet cavity, and then through the channels to the parts of the connecting rod and crank group, to the crankshaft bearings and the gas distribution mechanism.

In the case of lubrication with a "dry" sump, oil is poured into a barrel. From there, it gets to the rubbing surfaces with the help of a pump. Part of the oil flowing into the crankcase is pumped out by an additional pump and returned to the tank.

To purify the oil from various wear products, the engine has a filter. In addition, if necessary, install cooling filters, because the oil temperature during operation can rise very much.

The principle of operation of 2 and 4-stroke engines

Before saying which engine is better, consider the design of engines.

The stroke of the internal combustion engine cycle is the stroke of the piston from one dead center to another. One stroke corresponds to a 180-degree rotation (half-turn) of the crankshaft. With a 4-stroke process, the working cycle is carried out in two revolutions of the shaft, with a 2-stroke process - in one.

The same 4 cycles are present: intake - compression - expansion - release. First, the intake valve opens, the piston goes down, under the action of the resulting vacuum, a fresh air-fuel mixture or air enters the cylinder - this is the intake stroke. Then the valve closes, the piston goes up - compression occurs. The next stroke: the compressed mixture is ignited by a spark, the piston goes down under the influence of this - this is an expansion, or a working stroke of the piston. The engine does useful work during the expansion cycle. Then the piston goes up, the exhaust valve opens, through which the combustion products of the fuel go into the atmosphere - this is the exhaust stroke.

In the case of a two-stroke process, things are no longer so simple. The cycles are conditionally called compression and expansion. As you can see, there was no place for separate intake and exhaust strokes. This is no coincidence. Although there are intake and exhaust processes in a two-stroke engine, for their implementation it is necessary that the pressure at the inlet to the cylinder be above atmospheric. That is, a forced boost is needed. Those who are familiar with two-stroke motorcycle gasoline engines may argue that there are no turbo or mechanical compressors on motorcycles. There really is no separate compressor in a two-stroke motorcycle. The compressor function is assigned to the engine crankcase.

In simple motorcycle engines, there are no valves in the cylinder head, instead there are inlet and outlet ports in the cylinder walls, blocked by the piston body. The inlet windows are connected to the carburetor not directly, but through bypass channels that open into the crankcase. During the upward stroke of the piston, the lower edge opens the window on which the carburetor is located, the working mixture, under the action of the vacuum created by the upward piston, rushes into the crankcase. When the piston goes down, it closes this window, the working mixture begins to compress. The piston goes further down, opening the bypass windows, the working mixture is supplied under pressure to the cylinder, where it displaces the exhaust gases into the exhaust window. The piston goes up again, and the processes under its bottom are repeated, and at this time the working mixture is compressed in the cylinder. The compressed mixture is then ignited by the spark plug and the piston moves down on its expansion stroke, or power stroke.

The 2-stroke motor responds more quickly to the throttle. In 4-stroke cycles, the piston needs to make 2 full revolutions to complete a full cycle, while in 2-stroke cycles, only one.

Push-Pull Drawbacks

1. Greater fuel consumption. Recall that the approximate consumption can be calculated by the formula: for 2 cycles 300 grams per horsepower for 4 cycles 200 grams.

2. Noisy. At maximum speed, 2-stroke engines tend to run a little louder than 4-stroke engines.

3. Comfort. 4-stroke engines do not vibrate as much at low speeds (Only applies to two-cylinder engines. Single-cylinder and 2-stroke and 4-stroke engines vibrate about the same) and do not smoke as much as 2-stroke engines. Smoke is an important point, especially if you like to troll.

4. Durability. Pretty controversial point. There is an opinion that 2-stroke motors are less durable. On the one hand, this is understandable, because the oil for lubricating the rubbing elements of the engine is supplied together with gasoline, which means it does not work as efficiently, unlike 4-stroke engines, where the rubbing elements literally float in the oil. But on the other hand, a 4-stroke engine is much more complicated in design than a competitor, it consists of a much larger number of parts, and no one has yet canceled the golden principle of mechanics "The simpler the more reliable".

And again, but in more detail:

What is the difference between 2T and 4T engines?

Let's start with the principle of action. Any internal combustion engine has a piston that turns the crankshaft (and ultimately the wheels) through the connecting rod, driven by the energy of combustion of fuel vapor mixed with air (combustible mixture).

In a 2T engine, the process of filling the cylinder with a fresh combustible mixture, compressing it, igniting it, power stroke (when the combustion energy forces the piston down, rotating the crankshaft) and exhaust gases is released in two cycles.

First beat. The piston goes up, compressing the fuel mixture. The combustible mixture ignites. Second cycle, working stroke. The expanding gases push the piston down. When it is at the bottom, it opens the exhaust and intake ports in the cylinder walls. Exhaust gases go into the muffler, their place is taken by a fresh fuel mixture and the first cycle is repeated. All this happens in one revolution of the crankshaft.

In a 4T engine, the process of filling the cylinder with a fresh combustible mixture, compressing it, igniting it, running it and exhausting it takes four cycles.

First stroke, inlet. The piston goes down, the intake valve opens, and the fuel mixture enters the cylinder. When the piston reaches the bottom position, the intake valve closes.

Second measure, compression. The piston goes up, both valves are closed, the fuel mixture is compressed. When the piston is at the top, the spark plug ignites the combustible mixture.

Third cycle, working stroke (expansion). The hot gases expand rapidly, pushing the piston down (both valves closed).

Fourth measure, release. By inertia, the crankshaft continues its rotation (for uniform rotation, weights are installed on the crankshaft - crankshaft cheeks), the piston goes up. At the same time, the exhaust valve opens and the exhaust gases exit into the exhaust pipe. In the upper position of the piston, the exhaust valve closes. These 4 cycles occur in two revolutions of the crankshaft.

They say that a two-stroke engine is more powerful and a scooter with it is more dynamic. It's right?

Yes. 2T engine for two turns of the crankshaft manages to use the energy of fuel combustion twice. Many believe that it is twice as powerful as a 4T engine. But pay attention, in a 2T engine, part of the cylinder is occupied by intake and exhaust windows, which means that the amount of fuel that will then burn out is less in volume than in a 4T engine, where the cylinder is one-piece. In the 2T engine, due to the simplicity of the design, the crankshaft is lubricated with oil added to gasoline. Oil in the working mixture reduces the energy released (oil burns worse). Due to the peculiarities of the intake-exhaust of the combustible mixture and exhaust gases in the 2T engine, more of the combustible mixture "flies into the pipe" without burning. In a 4T engine, this process is minimal due to a more complex intake-exhaust mechanism. As a result, 2T engines are indeed more powerful (but not twice as much), but their higher power is achieved in a narrower operating range of crankshaft speeds (that is, you start from a standstill, the scooter barely accelerates, then the so-called “pick up” occurs. ”, the scooter “shoots”, but quickly fades) and you will have to maintain a certain engine speed all the time for a dynamic ride. As you understand, the more powerful the 2T engine, the narrower the rev range, the finer the settings and the more expensive the engine. Either athletes (where it is more important to squeeze everything out now) or owners of chainsaws and lawn mowers (which are simpler and cheaper, the better) can enjoy the full benefits of a 2T engine. If you want to improve the dynamic performance of your scooter, you can install a kit to increase the engine displacement up to 70 cc. After the rework, your scooter will not yield to the 2T model and there will be more riding pleasure.

4T engine is less powerful, so it’s not interesting to ride such a scooter?

It follows from the previous answer that even a slightly less powerful 4T engine has a more favorable characteristic - it is "elastic". Immediately from the start of the movement, it will provide the scooter with “locomotive traction”, that is, you pick up speed smoothly and confidently without “dips” and “pickups”, and a confident set of speed will be available to you throughout the entire range of crankshaft speeds. The lack of power will affect only in the upper operating range of engine speeds, that is, when you "spit" at the limit. Just close to this driving mode, the 2T engine will produce maximum power. Tell me, how long will the equipment operated at the limit of its capabilities last? You do not feel sorry for the money for unscheduled repairs?

Is the 4T engine more reliable?

Undoubtedly.

In a 2T engine, the piston, piston rings and cylinder are actually consumables due to the design features - there are holes in the cylinder. Many scooters roll a 2T engine piston in a season, and a cylinder in two. In a 4T engine, you will forget about it. 4-5 seasons on one piston 4T engine is the norm.

Due to better lubrication (oil is supplied to critical parts not mixed with gasoline, but by spraying or supplying under pressure), a 4T engine is designed for a longer service life. A more complex valve mechanism for the intake and exhaust of gases works more clearly, requires simple and infrequent maintenance.

Is a 4T engine more economical?

Certainly. A 50cc 2T model with decent performance (power 4-5 hp), consumes 3.5 liters of gasoline per 100 km. Plus oil. A 4T engine with a power of 3 hp. "eat" 2.2 liters. gasoline. Oil is not consumed at all.

Not only the speed of emptying your wallet depends on this, but also the mileage at one gas station. Since the scooter tanks are about the same, a 6 liter tank is enough for you to drive 100 km more on a 4T scooter without stopping.

Who would you recommend to buy such a scooter?

First of all, those who will go to the country, to the forest and through the fields for walking and fishing, in the city to work at rush hour. The scooter will give you the opportunity to feel free. For a teenager, this is a toy that is the first step in mastering the world of two-wheeled vehicles and the pleasures that this promises. In any case, it is better to start with reliable, economical and inexpensive equipment, so that the joy of owning a scooter is not overshadowed by a high price, frequent repairs, and high gas costs.