CDI stands for Capacitor Discharge Ignition which is known as the ignition system in a series of motorcycle engines. This ignition takes place in the combustion chamber which utilizes energy from the capacitor. This energy is then used to produce a high voltage on the ignition valve so that this results in a spark in the plug. For more insight about this, the function of the CDI and how it works will be discussed in this article.
In general, the function of the CDI is to distribute and cut off the flow of electric current to the motorcycle. In this sense, CDI regulates the availability of electric current when the engine is turned on or off. The CDI coil that gets a high voltage from the capacitor will cause electric sparks to spark in the plug. The higher the energy of the channeled capacitor, the stronger the spark in the plug to ignite the fuel.
The function of the CDI ignition system is very important for the quality of the motorcycle’s work. This ignition system needs precise timing, for that the CDI is made to regulate it. A good ignition system will completely burn fuel vapor so that it does not produce pollutants and produces optimal heat.
Heat is needed for a motor system that is designed in such a way as to convert chemical energy into heat energy which is then converted into motion energy in the motorcycle.
Therefore, the use of the right CDI components will greatly affect fuel consumption and motorcycle performance. There are many kinds of CDI with certain types which are adapted to the type of motorbike as well. Several types of CDI are racing limiter, racing un-limiter, programmable, and standard. These types of CDI are only of different types but their function is still the same.
CDI has two ignition systems, which are CDI with AC power and CDI with DC power.
- CDI with AC power utilizes the main voltage coming from the spool as it is known that the electric current generated by the spool is AC. This AC is used in this ignition system.
- CDI with DC power utilizes DC direct voltage and electric current from the rectifier regulator on the motorcycle. This electric current initially comes from the spool as well but is converted first by the rectifier regulator into DC which is then used by the ignition system.
Both of these systems have the same circuit and components. This is because the CDI is equipped with a diode component that functions as a current converter so that it can be passed by AC or DC.
Before further discussion about how the CDI works, it is necessary to know the components of the CDI and their functions to better understand how the CDI in a motorcycle works in the next discussion.
- Batteries have a function as energy storage and electric current. For injection motorcycles, this component is used to activate the ECU. The electricity stored in this battery comes from the spool.
A spool is a component that is in the form of a static coil and is located on the inside of the magnetic rotor. The magnetic rotor is in the form of a drum that is connected to the engine crankshaft. These two components have a function to change the rotation channel on the engine crank and convert it into AC.
- Pulse igniter or pick up coil is a component for capturing a signal or timing when igniting. Then this component will send the signal to the SCR in the CDI unit.
- Voltage converter is a component to convert a higher voltage. In other words, this component maximizes the discharge current so that it has a high voltage.
- CDI unit is the main component in the CDI ignition mechanism. This component has a role to transmit voltage to the coil with the concept of discharge. In this component, there is a capacitor that works to absorb and store electric current and release it later when needed.
- Key works as a motor ignition switch. The key functions to turn on and turn off the engine.
- Fuse has a function as a safety circuit in case of a short circuit or short to ground. In the ignition system, the fuse can protect the CDI unit to keep it in a safe condition in the event of a short electric current. The way it works is by automatically breaking the thin wire in the fuse when the current exceeds the capacity.
- Ignition coil serves to increase the electric voltage to 200KV through a spontaneous induction process. This component uses an up-stage transformer work system, which utilizes the number of turns in the coil (the secondary coil is more than the primary coil).
- Spark plug wire is useful as a distributor of high voltage electric current from the ignition coil component. This cable has a diameter of about 5 mm.
- Cop spark plug is the end of the spark plug wire that connects between the spark plug and the spark plug wire. In short, this section is only a joint.
- Spark plug is an important component in addition to the CDI unit. In the ignition system, the spark plugs play a role in creating electric sparks in the combustion chamber which are obtained from electromagnetic induction from the coil so that fuel combustion can occur and the engine starts.
How Motorcycle’s CDI Works
After knowing the components of the CDI, we will easily understand the working concept of this CDI. When the ignition is turned on, the CDI unit battery will flow the electric current. This current then enters the converter so that the voltage can be increased up to 300 volts. In this condition, the engine is not turned on because energy is stuck in the capacitor.
On CDI’s AC, when the connector lock is On, the pick-up coil will deliver the PWM signal to the machine according to the RPM frequency. This is what causes a pulse with a certain frequency to be sent to the SCR. When the SCR receives a time signal from a pulse igniter, a capacitor current will be generated.
When the capacitor circuit is connected to the ignition coil, there will be two conditions; the battery circuit will be disconnected and the second voltage in the ignition coil will immediately flow to the primary coil quickly so that a large magnetic power will arise in the primary coil spontaneously.
This magnetism will propel the induction of the secondary coil to produce a voltage of seven times. The voltage from the secondary coil is sent to the spark plug, causing an electric spark. This spark plays a role in the fuel combustion process in the motor so that the engine can start to work.
When the SCR gets a signal again, the battery current will be reconnected to recharge the capacitor in a short time. As for accelerating ignition, the rotor and pulse igniter play an important role. The rotor will adjust the rotation to the RP and the weight of the motor engine. This results in a signal from the pulse igniter which can still be used again.