When
it comes to automobiles there are various kinds of engines available. However,
majorly there are two types of engines, 2 stroke and 4 stroke.
A stroke is a process in which the distance is covered by the piston when it moves from the top dead center (TDC) to bottom dead center (BDC), or vice versa to produce power. A stroke is the main function in the engines which leads to the combustion process within an engine.
2 Stroke vs 4 Stroke
The main difference between 2 Stroke and 4 Stroke is basically how they are operated. The 4 stroke engines require a heavy flywheel, whereas 2 stroke engines require a lighter flywheel. Both the engines can also be differentiated on the basis of their use because 2 stroke engines are mainly used in scooters and mopeds whereas, 4 stroke engines are used in heavy vehicles or off-road vehicles.
Comparison Table Between 2 Stroke and 4 Stroke (in Tabular Form)
| Parameter of comparison | 2 Stroke | 4 Stroke |
|---|---|---|
| No. of crankshaft revolution | One | Two |
| Torque Generation | High torque | Low torque |
| Fuel’s Outlet and Inlet | Uses ports | Uses valves |
| Thermal Efficiency | Less thermal efficient | Higher thermal efficient |
| Cost | Cheaper | Expensive |
| Scavenging Process | No | Yes |
| Noise Production | Less | High |
| Space | More space required | Less space required |
What is 2 Stroke?
2 stroke engines are mainly used in scooters and mopeds but nowadays it is also being used in small engine tools and some kind of trimmers.
Its
name itself indicates its functioning, in order to power the engine there are
only two strokes which the engine performs i.e., the compression stroke and the
combustion stroke, therefore these engines are called 2 stroke engines.
In every single revolution of the piston, the spark plugs fire and power is produced once every 2- strokes of the piston. To complete the entire combustion cycle, 2 stroke engines performs five functions which are intake, compression, ignition, combustion, and exhaust this entire cycle is completed after two piston strokes.
The pressure is created on the carburetor when the fuel is pulled from it. A vacuum is created as the piston travels downwards to the cylinder, this opens up the exhaust ports and the pressurized fuel mixture went into your cylinder.
The piston then moves upwards to the cylinder to reach the spark plug. To generate the spark, the spark plug is used which will later heat the fuel and then sends the piston back down towards the cylinder, and open up the exhaust port.
The extra wear out goes out of the exhaust
port on the engine as soon as the piston moves back upwards to the cylinder, and
then new fuel is introduced into the cylinder.
In every single revolution of the crankshaft the crankshaft rotates to 360 degrees. In 2 stroke engines, there is an exhaust port in the combustion chamber. Hence, it does not need valves as the intake and exhaust are part of the compression and combustion of the piston.
Also, these engines do not have a separate chamber for the oil, therefore oil must be mixed with fuel in the proper amount. 2 stroke engines combust the fuel mixture in every rotation unlike other 4 stoke engines and these are faster than 4 stroke engines because they do not have valves and fire every piston revolution.
2 stroke engines have fewer parts which make it inexpensive and easy to manage. Thus, it also occupies less space. Their design is based on high power to weight ratio. 2 stroke engines can be positioned in any direction as you don’t need to worry about the oil flow from any of the valves.
Few applications of 2 stroke engines are:
- Equipment used in lawn and garden, bikes, jet skis
- Small outboard motors
- Radio-controlled model plans
What is 4 Stroke?
4 stroke engine is also a type of an internal combustion engine. 4 stroke engines have intake and exhaust valves, unlike 2 stroke engines that have ports for pulling in fuel and air. The successive strokes which take place in 4 stroke engines are suction, compression, power, and exhaust.
4 strokes are needed to complete the cycle in 4 stroke engines. The crankcase is an important part of the engine, in which the engine is kept separated from the chamber so that combustion can take place. And therefore, you only need to lubricate gears and other bearings of the engine by filling the oil into the oil reservoir.
When
the first stroke takes place it opens the intake valve, the piston travels down
towards the cylinder and pulls the fuel and air mixture from the carburetor.
This stroke which is performed here is known as the intake stroke.
After the intakes stroke is performed, the piston again starts moving in upwards direction to reach the cylinder and closes the intake valve. The spark plug gives off a spark to ignite the fuel mixture, just before the piston reaches the top dead center.
The compression stroke takes place when the piston goes to the top of the piston. As soon as the fuel ignites it forces the piston back down towards the cylinder. Power stroke gives the power to the engine its power.
The exhaust valve gets open when the piston is forced down. As soon as the valves get open the piston then travels upwards to reach the cylinder, once it reaches the cylinder the exhaust gases are emitted through the exhaust port available in the engine.
The piston will again move up towards the cylinder and begin the process all over again. Here you can see both compression and combustion stroke.
All the successive strokes are completed in the 2 revolutions of the crankshaft. And in this, the crankshaft rotates at 720 degrees.
4 strokes have more and very well reinforced parts. The performance of 4 stroke engines is very well. 4 strokes engines are majorly used in heavy-duty appliances and vehicles like buses, cars, and trucks.
4
stroke engines are less noisy and provide high power output. Its maintenance
cost is also low as compared to other engines.
Main Differences Between 2 Stroke and 4 Stroke
- The main difference between 2 stroke and 4 stroke engines is the way they operate i.e., the movement of the crankshaft and piston is the major difference between these two engines.
- Their performance, maintenance cost, and efficiency is also the major aspect to see their difference, as well as their uses.
- 4 stroke engines are less noisy and provide high power output. Its maintenance cost is also low as compared to 2 stroke engines.
- The applications of both the engines are also different. 2 stroke engines are used in small and light equipment and engines, whereas 4 stroke engines are used in heavy and offload equipment and engines.
- The space occupied by 4 stroke engines is quite high and not easy to manage, whereas 2 stroke engines are small and occupy less space. One can easily handle 2 stroke engines
Conclusion
Technically,
2 stroke and 4 stroke engines are essential and they basically have different
applications at different places.
However, if we see on the basis of performance 4 stroke engines are better with low maintenance and high power output.
Whereas,
2 stroke engine is less expensive, occupies less space and easy to operate and
handle. Hence, both the engines are having some pros and cons as per their
design and performance.
References
- https://bura.brunel.ac.uk/bitstream/2438/9742/1/Fulltext.pdf
- https://www.archives-pmr.org/article/S0003-9993(99)90098-9/pdf
- https://www.sae.org/gsdownload/?prodCd=981038