Ladies and gentlemen, start your engines and learn about the ignition coil, a type of step-up transformer key no pun intended to the operation of your car. Electric, solar-powered and alternate fuel vehicles may be the wave of the future, but for now most automobiles run on gasoline, which they burn in an internal combustion engine to convert into motion. For combustion to take place, a spark is needed to ignite the fuel mixture in the engine.
The heart of this system is a device called an ignition coil. This coil is a kind of transformer. Transformers transfer voltage from one circuit to another, either as a higher voltage as in a step-up transformer, of which the ignition coil is an example , or a lower voltage a step-down transformer. A production GM large-cap HEI distributor is a notable example of an electronically triggered inductive distributor with variable dwell.
Photo: Marlan Davis. As its name implies a "capacitive discharge" system uses a separate capacitor to store energy at a high voltage threshold as much as primary and 50, secondary volts in an MSD 8-Plus, for example , which is then discharged through the ignition coil. Capacitors charge far more quickly than a coil, and the best of these systems can fully charge up to as high as 15, engine rpm.
Invariably, a coil intended for use with a CD system has a different turns rate, internal resistance, and rise time compared to a coil used on a traditional inductive system.
For a discussion of capacitive discharge vs. Capacitive Discharge Ignition Systems. Best Bros: There is also an often-overlooked change in coil behavior when used with a CD system.
When teamed with a capacitor, the coil becomes a tuning device for the ignition system. By swapping in different coils with different levels of inductance, it's possible to improve power and on-track performance see " Coil Tuning " for a detailed explanation on how to do this. A "hot" coil runs More heat, more resistance. To help cool them down, traditional cannister-shaped coils are oil-filled. If oil starts leaking out, it's a sign that the coil's days are numbered.
Modern irregularly shaped performance and racing coils typically reject heat with epoxy potting. And the iron core is no longer a round tube in the new designs. For instance, MSD's E-core and U-core coils have proven to be more efficient than traditional canister configurations for radiating heat while stepping up the voltage between windings, due to their smaller and more enclosed area where the field collapses.
The iron core's laminations have many more thin metal layers to yield a higher-frequency coil with less energy loss. It takes an ignition village: In sum, to achieve maximum performance, the coil should be optimized for the type of ignition system employed inductive or capacitive discharge and distributor's switching mechanism points or electronic , expected engine operating rpm range, and duty cycle street, short-duration racing, or endurance racing.
A coil with the correct turns ratio to work right with one type of ignition system may not be the best solution for a different type of system. This ruins the new coils. The typical wiring for a three-wire ignition coil-on-plug assembly are battery voltage power supply, ground and control circuit trigger from the PCM to a transistor circuit in the coil on plug assembly. Four wire coil-on-plug assemblies can involve a lot of commonality also such as, the battery voltage power supply, two ground circuits and the control circuit trigger from the PCM to the solid state driver module.
Some applications may use one the four wires of the coil-on-plug assembly as a feedback circuit to verify proper ignition coil system integrity. Also, do not forget the condition of the spark plugs themselves as a contributing factor. When replacing an ignition coil that has failed, replacing the spark plugs and the other ignition coils is always recommended to prevent comebacks.
As each tooth of the armature nears the pickup coil, it creates a voltage that signals the electronic module to turn off the coil primary current. A timing circuit in the module will turn the current on again after the coil field has collapsed. When the current is off, however, the magnetic field built up in the coil is allowed to collapse, which causes a high voltage in the secondary windings of the coil. It is now operating on the secondary ignition circuit, which is the same as in a conventional ignition system.
Very different from conventional and electronic — coils sit directly on top of the spark plugs, no spark plug wires, and the system is electronic. The third type of ignition system is the distributorless ignition. The spark plugs are fired directly from the coils.
Spark plug timing is controlled by an ignition module and the engine computer. The distributorless ignition system may have one coil per cylinder or one coil for each pair of cylinders. Learn more about quality spark plugs , find your car part , or find where to buy your auto part today. The content contained in this article is for informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic.
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