In Yamaha's R1, crossplane crankshaft has been used. It have normal inline 4 cylinder engine like in other superbikes. You can able to see high power superbikes are fitted with inline 4 cylinder arrangement. For example Yamaha's R1, Suzuki's GSX R 1000, Honda's CBR 1000 RR, Kawasaki's ZX-10R and H2, BMW's S 1000 RR and in motorbikes with 1340 - 1400 CC range like Kawasaki's ZX-14R, Suzuki's Hayabusa. Like inline 4, there's also the V4 setup which is present in motorbikes like Ducati's Panigale V4 and in Aprilia's RSV4. Generally in inline 4 cylinder's arrangement, the crankshaft will be designed to hold two pistons at the top that is at Top Dead Center (TDC) and to hold other two pistons at down that is at Bottom Dead Center (BDC). Two pistons will be at 0° and the other two will be at 180°. But here in the crossplane crankshaft, each piston will be present at 90°. That is in every 90°, one piston will be present. It just look like two parallel twins joined together. Due to this arrangement, engines fitted with crossplane crankshaft have very aggressive and unique exhaust note.
Inline 4 cylinder
You might wonder why sports and high performance oriented motorbikes have multiple cylinders with various configurations like boxer arrangement, inline arrangement, V arrangement. The answer is power stroke. Yeah.... For example, consider a single cylinder engine. The power stroke exactly happens third in the sequence. In the one total combustion cycle (720°), the power stroke happens + or - 360°. During the whole 720°, at the third stroke (@ + or - 360°) the sparkplug burns the fuel air mixture thus making the piston to move downwards. What i'm trying to say is, at the whole 4 stroke, the power is obtained only at 3rd stroke. Other strokes will be happening only with the help of the momentum from the flywheel. But, in the case of 4 cylinder engine, the power stroke happens at each cylinder simultaneously. At every stroke, a power stroke will be obtained from anyone of the 4 cylinders. Thus inline 4 cylinders produce more power compared to any other setup.
As we all know, when rider twists the throttle, the torque will be generated. This torque is divided into two. First one is the combustion torque and second one is the inertial torque. Combustion torque is produced when the fuel air mixture is burnt and forcing the piston down. Inertial torque is the torque which is produced in the engine's crankshaft. The torque which the rear wheel experiences is the result of both combustion and inertial torque. Combustion torque varies according to the throttle input. But, inertial torque depends on the crankshaft rotation.
In a conventional inline 4 cylinder engine with flatplane crankshaft, the inertial torque increases with the engine RPM. At lower RPM band, the level of disturbance or interference from the rotating crankshaft is somewhat manageable. But, once the engine starts to run at higher RPM band, inertial torque becomes greater than the combustion torque. At higher RPM band, rider needs more combustion torque. But due to the addition of inertial torque which cannot be controlled, the output torque will become disordered.
To eliminate this problem, crossplane crankshaft has been designed and developed. By differing the position of crankpins at the regular interval of 90°, the fluctuation created by the inertial torque is eliminated. Due to this, rider is able to achieve linear power delivery and good amount of traction in all RPM band. This crossplane crankshaft also provides a irregular firing order which results in more vibrations. To compensate and eliminate the vibrations produced, the design is added with the optimized balancer shaft.
pros
* Smooth running due to a continuous crank rotation as a result of every cylinder firing at 90°.
* Capable of producing high optimized torque at low RPM.
* Unique and aggressive exhaust note.
Cons
* Heavy counterweight results in additional mass.
* Large crankcase
* Lower revving limit.
Inline 4 cylinder
You might wonder why sports and high performance oriented motorbikes have multiple cylinders with various configurations like boxer arrangement, inline arrangement, V arrangement. The answer is power stroke. Yeah.... For example, consider a single cylinder engine. The power stroke exactly happens third in the sequence. In the one total combustion cycle (720°), the power stroke happens + or - 360°. During the whole 720°, at the third stroke (@ + or - 360°) the sparkplug burns the fuel air mixture thus making the piston to move downwards. What i'm trying to say is, at the whole 4 stroke, the power is obtained only at 3rd stroke. Other strokes will be happening only with the help of the momentum from the flywheel. But, in the case of 4 cylinder engine, the power stroke happens at each cylinder simultaneously. At every stroke, a power stroke will be obtained from anyone of the 4 cylinders. Thus inline 4 cylinders produce more power compared to any other setup.
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| Flatplane arrangement |
So why crossplane?
In the year 2009, Yamaha has used the crossplane crankshaft in their production sports bike R1. As i said, flatplane crank setup in a inline 4 cylinder will have crankpins at 180°. First and fourth cylinder's crankpin will be at 0°. Second and third cylinder's crankpin will be at 180°. Which means, first and fourth cylinder's piston will be at TDC where second and third cylinder's piston will be at BDC at the same time. The firing order will be 1-3-4-2. But in the engine fitted with crossplane crankshaft, crankpins will be present at each 90°s. In crossplane setup, first cylinder's piston will be at TDC. Second and third cylinder's piston will be at middle of the combustion chamber. Fourth cylinder's piston will be at the BDC. The firing order in this arrangement is 1-3-2-4.
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| Crossplane arrangement |
As we all know, when rider twists the throttle, the torque will be generated. This torque is divided into two. First one is the combustion torque and second one is the inertial torque. Combustion torque is produced when the fuel air mixture is burnt and forcing the piston down. Inertial torque is the torque which is produced in the engine's crankshaft. The torque which the rear wheel experiences is the result of both combustion and inertial torque. Combustion torque varies according to the throttle input. But, inertial torque depends on the crankshaft rotation.
In a conventional inline 4 cylinder engine with flatplane crankshaft, the inertial torque increases with the engine RPM. At lower RPM band, the level of disturbance or interference from the rotating crankshaft is somewhat manageable. But, once the engine starts to run at higher RPM band, inertial torque becomes greater than the combustion torque. At higher RPM band, rider needs more combustion torque. But due to the addition of inertial torque which cannot be controlled, the output torque will become disordered.
To eliminate this problem, crossplane crankshaft has been designed and developed. By differing the position of crankpins at the regular interval of 90°, the fluctuation created by the inertial torque is eliminated. Due to this, rider is able to achieve linear power delivery and good amount of traction in all RPM band. This crossplane crankshaft also provides a irregular firing order which results in more vibrations. To compensate and eliminate the vibrations produced, the design is added with the optimized balancer shaft.
pros
* Smooth running due to a continuous crank rotation as a result of every cylinder firing at 90°.
* Capable of producing high optimized torque at low RPM.
* Unique and aggressive exhaust note.
Cons
* Heavy counterweight results in additional mass.
* Large crankcase
* Lower revving limit.
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