Motorcycle Noise Reduction
LEADING THROUGH KNOWLEDGE
ENGINE EFFICIENCY
Heat engines, like steam engines, turn thermal energy into mechanical work repeatedly.
The process starts out at a high operating temperature and ends up at a lower operating temperature.
The heat engine takes the input heat used to raise the temperature to produce work, while some dissipate as exhaust.
Heat released as exhaust raises the temperature of the heat engine, starting the cycle once more.
First law of Thermodynamics states that change in the thermal energy of a system is equal to heat and work. In the case of a heat engine, however, the change in thermal energy is zero because the temperature always returns to where it started from.
This also links to the idea of efficiency within a functional system. The more work produced and less heat released, the more efficient the system is in utilizing the input heat. It is important for an engine to be efficient because then we wouldn't be wasting energy.
In the case of motorcycle engines and their sound productions, for example, an engine's input heat is 10 kJ at 500K and its exhaust heat is 2 kJ at 300 K. We want to find out the efficiency of the engine by using this equation:
Efficiency = 1 - exhaust heat/input heat
1 - 2kJ/10kJ = 0.8 = The engine is 80% efficient, meaning, 80% of its input heat goes to work and the rest 20% is released as exhaust heat.
The ideal efficiency, however, is:
E = 1 - 300K/500K = 0.4
What this means is that it is impossible for this engine to have an efficiency over 0.4, meaning, the data given to us of the engine is false.
Torque in a Motorcycle
The force we use to apply to the pedal with our leg muscles is comparable to the crankshaft.
There is a piston in the motorcycle that moves up and down. The force that continues its movement is from the fuel that's burned. Connected to the piston is a rod that's connected to the crankshaft. The initial force we apply to the pedal with our leg muscles is comparable to that first kick to the engine and start the process of fuel consumption.
The amount of torque is expressed in Newton meters. In a motorcycle, there often is a number for maximum torque and the number of revolutions per minute at which that torque is delivered (in rpm).
A motorcycle's maximum torque, therefore, is the rpm where the fuel is burned most efficiently. It's at that rpm where the piston delivers the maximum torque on the crank (usually at 90 degrees).
