You might be wondering why several motorbikes from the manufacturers have high cc, but low power output. It all depends on the engine architecture. Everyone of us is familiar with the motorbike with two different characteristics. First one is the high revving motor which is capable of producing more power in all RPM bands. On the other hand, we have engines which is not much capable of producing more power at higher RPMs but much better for producing the torque at low ends. The bore and stroke of the engine also plays an important role in deciding this parameter and in this post, let's see something about the long stroke and short stroke engines.
Bore and stroke of the engine
To understand about the short and long stroke engines, some of the basics should be gained about the bore and stroke of the engines. So, the bore of the engine refers to the measurement of the cylinder sleeve diameter in which the piston reciprocates. Stroke refers to the distance travelled by the piston from the Top Dead Center (TDC) to the Bottom Dead Center (BDC) of the cylinder. During the combustion cycle, the piston reciprocates in the cylinder which is connected to the crankshaft with the help of con rod thereby making the vehicle to move.
Based on the bore to stroke ratio, engine is classified into three types namely
* Square engine
* Under square engine
* Over square engine
Over square engine / short stroke engine
In this configuration, the stroke will be shorter than the bore of the engine which means that the piston has to move lesser as it has a wider bore. Due to this, the inertial stress is less compared to any other configuration and it creates the ability for the engine to rev at higher RPMs. With a big bore dimension, there'll be more space for fitting the better intake and exhaust valves on the head. Engines with bigger valves and big bore results the engine capable of revving more and to produce more power. These type of engine generates its peak power at higher RPM band which suits for the light weight high power motorbikes which is to meant to be ripped off on the tracks. As it contributes a top end power, low end torque is not good which affects the tractability of the vehicle at lower speeds. For example, Bajaj's 200NS have the bore of 72mm and the stroke of 49mm only.
Under square engine / long stroke engine
As the name tells, stroke will be higher compared to the bore. In this configuration, the piston has to travel longer for the given displacement. Because of this, the inertial stress will be higher, so this engine will not rev as high as a short stroke engine. Due to the short bore of the engine, less amount of space is present for fitting the bigger valves which affects the feeding of more fuel air mixture to the combustion chamber. Compared to the short stroke engines, long stroke engines are capable only for generating less power and accelerate very slowly. But, this long stroke engines have other advantages. Low end torque of the engine is very much good than that of the short stroke engines. Motorbikes which comes under tourer and cruiser category use this type of engines which is very much essential for carrying more load. For example, Royal Enfield's Classic 350 have 90mm of stroke and 70mm of bore.
Square engine
Both sides of the square are equal, as we all know. In square engines, the bore and stroke of the engine have almost same dimensions. This type of engine contributes a good balance between the torque and acceleration. For example, Yamaha's FZ have the bore of 57.3mm and stroke of 57.9mm. The dimensions are almost similar. This type of engines are known as square engines.
I hope now the doubts in difference between the long and short stroke engine has been flushed out and if you have any doubts, comment below and if you have any suggestions or corrections, mail me...
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Bore and stroke of the engine
To understand about the short and long stroke engines, some of the basics should be gained about the bore and stroke of the engines. So, the bore of the engine refers to the measurement of the cylinder sleeve diameter in which the piston reciprocates. Stroke refers to the distance travelled by the piston from the Top Dead Center (TDC) to the Bottom Dead Center (BDC) of the cylinder. During the combustion cycle, the piston reciprocates in the cylinder which is connected to the crankshaft with the help of con rod thereby making the vehicle to move.
Based on the bore to stroke ratio, engine is classified into three types namely
* Square engine
* Under square engine
* Over square engine
 |
Over square engine / short stroke engine
In this configuration, the stroke will be shorter than the bore of the engine which means that the piston has to move lesser as it has a wider bore. Due to this, the inertial stress is less compared to any other configuration and it creates the ability for the engine to rev at higher RPMs. With a big bore dimension, there'll be more space for fitting the better intake and exhaust valves on the head. Engines with bigger valves and big bore results the engine capable of revving more and to produce more power. These type of engine generates its peak power at higher RPM band which suits for the light weight high power motorbikes which is to meant to be ripped off on the tracks. As it contributes a top end power, low end torque is not good which affects the tractability of the vehicle at lower speeds. For example, Bajaj's 200NS have the bore of 72mm and the stroke of 49mm only.
Under square engine / long stroke engine
As the name tells, stroke will be higher compared to the bore. In this configuration, the piston has to travel longer for the given displacement. Because of this, the inertial stress will be higher, so this engine will not rev as high as a short stroke engine. Due to the short bore of the engine, less amount of space is present for fitting the bigger valves which affects the feeding of more fuel air mixture to the combustion chamber. Compared to the short stroke engines, long stroke engines are capable only for generating less power and accelerate very slowly. But, this long stroke engines have other advantages. Low end torque of the engine is very much good than that of the short stroke engines. Motorbikes which comes under tourer and cruiser category use this type of engines which is very much essential for carrying more load. For example, Royal Enfield's Classic 350 have 90mm of stroke and 70mm of bore.
Square engine
Both sides of the square are equal, as we all know. In square engines, the bore and stroke of the engine have almost same dimensions. This type of engine contributes a good balance between the torque and acceleration. For example, Yamaha's FZ have the bore of 57.3mm and stroke of 57.9mm. The dimensions are almost similar. This type of engines are known as square engines.
I hope now the doubts in difference between the long and short stroke engine has been flushed out and if you have any doubts, comment below and if you have any suggestions or corrections, mail me...
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