hondafox440
11-24-2003, 07:02 PM
Basic CDI Ignition overview.
Electronic ignition systems, using a CDI are a much welcomed change to the points based ignition systems of the yesteryear. These new systems are more reliable than points, wear slower, and are less complicated in design. However, the parts that go into an electronic ignition system are more complex and expensive that those of a points ignition system
There are three main parts to an electronic ignition system:
The stator, which contains AC (alternating current) generating coils, and a pick up.
The CDI, which creates a high voltage electrical charge and sends it to the spark plug.
The flywheel, which contains several magnets that rotate around the stator.
A basic understanding of electricity is needed to understand your bike's ignition system. Electricity is the flow of electrons in a closed circuit. A closed circuit means the electrons have a complete path to travel in. For example, a wire placed from the positive (+) end of a battery, to the negative end of the battery (-), is a closed or complete circuit. A wire that is simply attached to the postive end of the battery at one end, and nothing at the other end of the wire is NOT a complete circuit.
*Rememeber*
1)Electrons must flow in a complete circuit
Conductors are materials that allow electrons to flow through them easily. Copper and gold are good conductors. Insulators are materials that do NOT allow electrons to flow through them easily. Examples of insulators are glass, rubber, or plastic. Voltage is the electrical pressure that is created when electrons (negatively charged) are separated from protons (positively charged). Remember that like charges (postive and positive) repel each other, and unlike charges (negative and positive) atract each other. Voltage is measured in the unit volts. Current is the flow of charged particles in a circuit, and is measured in amperes, or amps. Another way to think of current is the amount of electricity that can flow by a point in a given time. When voltage is applied to a circuit, and there is a path (current) for the electrons to move on, they move from the negative terminal to the postive terminal.
Alternating Current (AC) is the type of electricity that is delivered you your home. In AC, the voltage varies over time - it does not stay the same. This means that the voltage may spike and drop hundreds of times a second. Think of AC as a mountain range, with peaks and valleys. The voltage is constantly changing, going up and down. /\/\/\/\/\
Direct Current (DC) is the type of electricity that is created by batteries. In DC, the voltage does not vary over time - it is always the same. That means that a 9V battery ALWAYS produces 9 volts. ---------
*Remember*
1)Voltage is the "power" of the electricity.
2)AC voltage always varies.
3)DC voltage always stays the same.
Now, how does your engine create electricity? The most common way to create electricity is by spinning spools of wire through a magnet. This is what happens in power plants. Your engine does a scaled down version of this, with the stator and flywheel. Remember now that the stator contains AC generating coils. These coils are basically just coils of wire. The flywheel has magnets on it. The flywheel is connected tot he crankshaft of the engine, so as the engine runs, the flywheel rotates around the stator, which is stationary. This rotating action creates an electro magnetic field, and thus electricity is created in the same way it is at the power plant. Now that we have electricity, we need to turn that into a spark for the spark plug. This is where the CDI and coil come in. The electricity that is generated at the flywheel is routed up to the CDI by wires. Inside the CDI, the AC voltage is transformed into DC current. This DC current is then sent to a capacitor that is also located in the CDI. You can think of the capacitor as a storage tank for electricity. It stores energy until the "correct" voltage is reached. This varies between CDIs, but let's use 250V for this example. So when the capacitor gets 250V of electricity in it, it releases it all at once into the coil, which is correctly called the ignition coil. Inside the coil are 2 windings of wire, called the primary winding and the secondary winding. These windings are proportional to each other, with the secondary winding being much longer, even though it resides inside of the primary winding. For this example we will use 100:1, meaning the secondary winding is 100 times longer than the primary winding. There is also a magnetic field inside the ignition coil, created by the primary and secondary windings. This magnetic field is called the flux field. When voltage is passed through the primary winding, this magnetic field collapses and a voltage spike happens. This is when the ratio of primary to secondary winding comes into play, and the coil acts like transformer and steps the voltage up immensly. In this case, it would increase it by 100 times. Multiply that by the voltage that entered (250), and you have 25,000 volts leaving the coil. Where does this voltage go? It is fed into the spark plug. The benefits of the CDI system over the points system is apparent here because of how easy and precise it is to control the duration of the spark. The stronger (hotter) and faster the spark, the better.
So, as an overview.
Electricity is created by the flywheel spinning around the stator. The electricity is fed into the CDi, where it is released in a controlled pulse to the coil. The coil acts like a transformer and steps the voltage up, and feeds it into the spark plug.
There you have it. It's actually a relatively simple design, since there are no batteries involved. If your machine has a battery or lights, some of the electricity is routed to the alternator (changes AC current to DC) and to the battery from the stator, and some is routed to the lights from the stator.
Electronic ignition systems, using a CDI are a much welcomed change to the points based ignition systems of the yesteryear. These new systems are more reliable than points, wear slower, and are less complicated in design. However, the parts that go into an electronic ignition system are more complex and expensive that those of a points ignition system
There are three main parts to an electronic ignition system:
The stator, which contains AC (alternating current) generating coils, and a pick up.
The CDI, which creates a high voltage electrical charge and sends it to the spark plug.
The flywheel, which contains several magnets that rotate around the stator.
A basic understanding of electricity is needed to understand your bike's ignition system. Electricity is the flow of electrons in a closed circuit. A closed circuit means the electrons have a complete path to travel in. For example, a wire placed from the positive (+) end of a battery, to the negative end of the battery (-), is a closed or complete circuit. A wire that is simply attached to the postive end of the battery at one end, and nothing at the other end of the wire is NOT a complete circuit.
*Rememeber*
1)Electrons must flow in a complete circuit
Conductors are materials that allow electrons to flow through them easily. Copper and gold are good conductors. Insulators are materials that do NOT allow electrons to flow through them easily. Examples of insulators are glass, rubber, or plastic. Voltage is the electrical pressure that is created when electrons (negatively charged) are separated from protons (positively charged). Remember that like charges (postive and positive) repel each other, and unlike charges (negative and positive) atract each other. Voltage is measured in the unit volts. Current is the flow of charged particles in a circuit, and is measured in amperes, or amps. Another way to think of current is the amount of electricity that can flow by a point in a given time. When voltage is applied to a circuit, and there is a path (current) for the electrons to move on, they move from the negative terminal to the postive terminal.
Alternating Current (AC) is the type of electricity that is delivered you your home. In AC, the voltage varies over time - it does not stay the same. This means that the voltage may spike and drop hundreds of times a second. Think of AC as a mountain range, with peaks and valleys. The voltage is constantly changing, going up and down. /\/\/\/\/\
Direct Current (DC) is the type of electricity that is created by batteries. In DC, the voltage does not vary over time - it is always the same. That means that a 9V battery ALWAYS produces 9 volts. ---------
*Remember*
1)Voltage is the "power" of the electricity.
2)AC voltage always varies.
3)DC voltage always stays the same.
Now, how does your engine create electricity? The most common way to create electricity is by spinning spools of wire through a magnet. This is what happens in power plants. Your engine does a scaled down version of this, with the stator and flywheel. Remember now that the stator contains AC generating coils. These coils are basically just coils of wire. The flywheel has magnets on it. The flywheel is connected tot he crankshaft of the engine, so as the engine runs, the flywheel rotates around the stator, which is stationary. This rotating action creates an electro magnetic field, and thus electricity is created in the same way it is at the power plant. Now that we have electricity, we need to turn that into a spark for the spark plug. This is where the CDI and coil come in. The electricity that is generated at the flywheel is routed up to the CDI by wires. Inside the CDI, the AC voltage is transformed into DC current. This DC current is then sent to a capacitor that is also located in the CDI. You can think of the capacitor as a storage tank for electricity. It stores energy until the "correct" voltage is reached. This varies between CDIs, but let's use 250V for this example. So when the capacitor gets 250V of electricity in it, it releases it all at once into the coil, which is correctly called the ignition coil. Inside the coil are 2 windings of wire, called the primary winding and the secondary winding. These windings are proportional to each other, with the secondary winding being much longer, even though it resides inside of the primary winding. For this example we will use 100:1, meaning the secondary winding is 100 times longer than the primary winding. There is also a magnetic field inside the ignition coil, created by the primary and secondary windings. This magnetic field is called the flux field. When voltage is passed through the primary winding, this magnetic field collapses and a voltage spike happens. This is when the ratio of primary to secondary winding comes into play, and the coil acts like transformer and steps the voltage up immensly. In this case, it would increase it by 100 times. Multiply that by the voltage that entered (250), and you have 25,000 volts leaving the coil. Where does this voltage go? It is fed into the spark plug. The benefits of the CDI system over the points system is apparent here because of how easy and precise it is to control the duration of the spark. The stronger (hotter) and faster the spark, the better.
So, as an overview.
Electricity is created by the flywheel spinning around the stator. The electricity is fed into the CDi, where it is released in a controlled pulse to the coil. The coil acts like a transformer and steps the voltage up, and feeds it into the spark plug.
There you have it. It's actually a relatively simple design, since there are no batteries involved. If your machine has a battery or lights, some of the electricity is routed to the alternator (changes AC current to DC) and to the battery from the stator, and some is routed to the lights from the stator.