From the modern classics to the adventure tourers, the 270 degree parallel twin engines are used everywhere these days. Unlike other parallel twins, everybody loves this 270° parallel twin's exhaust which is a pure eargasm. Since the development of IC engines, many configurations has been designed and implemented. We have inline arrangement, V arrangement, boxer arrangement and so on. Especially in cruiser and in mid range motorbikes, parallel twin arrangement is used widely. There's something in this parallel twin cylinder arrangement which plays a major role. Yeah... Its nothing but the crank angle. We have 180° crank angle, 270° crank angle and 360°. But 270° crank angle is something different and very popular. Why?... Here in this post, let's see something about the 270° crank angle in parallel twin motors.
Comparing to the V twin or flat twin, parallel twin is easy to manufacture and easy to maintain. It stands out from other configurations in terms of both power and torque. You may think about the number 270 and what it refers to and what does the term crank angle mean.
Crank angle
Crank angle denotes the position of engine's crankshaft in relation to the piston which is travelling inside the engine's cylinder wall. This crank angle is measured in degrees. It is very much useful in determining the ignition timing, valve operating sequence and delivery of fuel in the fuel injected vehicles.
270 degree
The term 270° refers to the ignition timing. Ignition timing denotes the angular position of the crankshaft relative to Top Dead Center (TDC) of the cylinder. In other words we can say, it is the crank angle at which the sparkplug ignites the fuel air mixture present inside the combustion chamber at the end of the compression stroke. To understand about the 270° parallel twins, let's see about other two configurations first.
In a typical parallel twin engine with 180° crank, ignition takes place in each cylinder at 180° and at 540°. Because of this angle, it offers very uneven firing interval. Due to this, it produces high unbalanced vibrations compared to any other setup. The engine fitted with 360° crank have even firing order compared with 180° crank setup. Since both the piston will reciprocate at the same time, it has the mechanical balance of both piston as the single one. To cancel the vibration and force produced, a balancer shaft will be present. In this setup, firing happens at 360° and at 720°. Even though it is better than 180° setup, it still lacks smooth power delivery at all RPM band. This is where 270° comes into play. In the engine with 270° setup, firing happens at 270° and at 450°. This is exactly followed in the 90° V twin setup. That's why 270° parallel twins have unique exhaust note. It offers a better engine balance than the 360° and 180° crank. But it still requires a balancer shaft at higher RPM band to neglect the vibrations produced completely. In 360° and in 180° arrangement, both the piston stops at one spot simultaneously. But in 270° setup, when one piston is at stationery, the other one will be moving. This provides a good primary balance compared to other two setups making it much smoother. Since one piston is always moving, the crank speed fluctuates less during the cycle which results in linear torque delivery in the driveline and it provides good traction to the rear wheel.
V twin setup is thinner than other configurations. Then you might be questioning why manufacturers are not implementing this V twin setup in motorbikes. As i said previously, parallel twin configuration is simple in design and easy to manufacture & maintain where V twin setup is much more complicated. Parallel twins are most often used in cruiser based motorbikes and in retro modern motorbikes which means it should have retro appearance with modern features and high power. In this case, it is best to go for parallel twins because it consumes less space and looks simple where V twin setup need a lengthy profile which suits for a sports bike.
Comparing to the V twin or flat twin, parallel twin is easy to manufacture and easy to maintain. It stands out from other configurations in terms of both power and torque. You may think about the number 270 and what it refers to and what does the term crank angle mean.
Crank angle
Crank angle denotes the position of engine's crankshaft in relation to the piston which is travelling inside the engine's cylinder wall. This crank angle is measured in degrees. It is very much useful in determining the ignition timing, valve operating sequence and delivery of fuel in the fuel injected vehicles.
270 degree
The term 270° refers to the ignition timing. Ignition timing denotes the angular position of the crankshaft relative to Top Dead Center (TDC) of the cylinder. In other words we can say, it is the crank angle at which the sparkplug ignites the fuel air mixture present inside the combustion chamber at the end of the compression stroke. To understand about the 270° parallel twins, let's see about other two configurations first.
In a typical parallel twin engine with 180° crank, ignition takes place in each cylinder at 180° and at 540°. Because of this angle, it offers very uneven firing interval. Due to this, it produces high unbalanced vibrations compared to any other setup. The engine fitted with 360° crank have even firing order compared with 180° crank setup. Since both the piston will reciprocate at the same time, it has the mechanical balance of both piston as the single one. To cancel the vibration and force produced, a balancer shaft will be present. In this setup, firing happens at 360° and at 720°. Even though it is better than 180° setup, it still lacks smooth power delivery at all RPM band. This is where 270° comes into play. In the engine with 270° setup, firing happens at 270° and at 450°. This is exactly followed in the 90° V twin setup. That's why 270° parallel twins have unique exhaust note. It offers a better engine balance than the 360° and 180° crank. But it still requires a balancer shaft at higher RPM band to neglect the vibrations produced completely. In 360° and in 180° arrangement, both the piston stops at one spot simultaneously. But in 270° setup, when one piston is at stationery, the other one will be moving. This provides a good primary balance compared to other two setups making it much smoother. Since one piston is always moving, the crank speed fluctuates less during the cycle which results in linear torque delivery in the driveline and it provides good traction to the rear wheel.
V twin setup is thinner than other configurations. Then you might be questioning why manufacturers are not implementing this V twin setup in motorbikes. As i said previously, parallel twin configuration is simple in design and easy to manufacture & maintain where V twin setup is much more complicated. Parallel twins are most often used in cruiser based motorbikes and in retro modern motorbikes which means it should have retro appearance with modern features and high power. In this case, it is best to go for parallel twins because it consumes less space and looks simple where V twin setup need a lengthy profile which suits for a sports bike.
Tags
Random talks