Ignition system used to create a spark in the cylinder. Ignition system takes care of the spark timing and all advance mechanism .
For a spark to jump between the spark plug ends , the voltage difference must be 10000-20000 volts. But the battery supplies 14 volts (not sure about this ). So the voltage must stepped up heavily . The below video will show a older type of ignition system with distributor type.
Short wordings on the above video )all are DC current
-Primary current flow from the battery to the ground this happens when the contact breaker is closed.
-When the contact breaker is opened ( by the cam) the current from battery cannot flow to the ground so them magnetic field in the primary coli destroys. While destroying the magnetic flux will be continuously change , causing a a emf to induce in secondary coil.
-At the same time the capacitor will discharge a huge voltage which will accelerate the destroying magnetic field.
Since no of coils on the secondary coil is more , higher voltage is produced in secondary coli ,which later flows through distributor and reaches spark plug. The spark plug is grounded by connecting to the engine casing or the chassis.
But in modern engine these system have been modified and used as Transistor control ignition , capacitive discharge ignition , digitalelectronic ignition.
Electronic fuel ignition uses a electronic module , which uses a series of sensors and actuators. the sensors are used to just visualize the working of sensors. They convert the parameters (temperature , Crankshaft , camshaft position , throttle position , air mass flow rate , Oxygen level in exhaust ) into electrical signals and fed them to engine. The output of these sensors are analog , so they converted to digital signal before feeding tho the ECU.
The engine makes decision based on sensor information , and controls the actuators ( ignition timing , throttle position if its is a Drive by wire, fuel pressure ) in the engine , to optimize based on the situation. They act as feedback system.
The engine and ECU has a set of preset values called as Engine fuel map. This is like a table which controls the Air fuel ratio with respect to engine Speed. Air fuel is controlled with injecting predefined quantity of fuel based on throttle position.
Most modern engine will have a ECU with sensors and actuators
Refer this to know more on engine fuel maps
A engine can work only a narrow range of RPM , but in actual scenario we require various speed and torque depending on situation.A transmission is device which can increase speed with expense of reduction in torque and increase in torque by reducing speed ( this is application of law of conservation of energy)
Gif files show gear speed reduction and speed increase , a combination of such gears form a gear train.
Do u remember the thing which i said in starting about two types of bikes, this comes under this topic .
Transmission in Motor bikes-