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Automotive Ignition Coil: Progress Through Efficiency

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Automotive Ignition Coil: Progress Through Efficiency Automotive Ignition Coil: Progress Through Efficiency he automotive ignition sys- tem is crucial to the internal Tcombustion engine’s operation and efficiency. At the heart of the entire ignition system is the ignition coil. To understand how ignition coils operate, it is important to have a general understanding of the basic principles of vehicle electronics. Direct Current (DC) vs. Alternating Current (AC) The primary winding of the For many years, this interruption ignition coil is wound with a small of the primary current was accom- number of turns creating a small plished by mechanically opening resistance. Applying battery volt- a contact called the “points” in a age to this coil causes a sizable DC synchronized sequence to send current to flow. The secondary coil high voltage pulses through a rotary has a much larger number of turns switch called the “distributor” to the and therefore acts as a step-up sparkplugs. One of the drawbacks of transformer. Rather than operating this process was that the interruption on AC voltages, this secondary of current in the primary coil generat- coil is designed to produce a large ed an inductive back-voltage in that voltage spike when the current in coil which tended to cause sparking the primary coil is interrupted. Since across the points. The system was the induced secondary voltage is improved by placing a sizable capac- proportional to the rate of change of itor across the contacts so that the the magnetic field through it, opening voltage surge tended to charge the a switch quickly in the primary circuit capacitor rather than cause destruc- FARADAY’S LAW AND to drop the current to zero will gener- tive sparking across the contacts. AUTOMOTIVE IGNITION ate a large voltage in the secondary Using the old name for capacitors, How do you obtain 40,000 volts coil according to Faraday’s Law. This this particular capacitor was called across a sparkplug in an automobile large voltage spike what is used in the “condenser”. when you have only 12 volts DC to the internal combustion engine to More modern ignition systems start with? The essential task of firing be sent to the spark plug. Once this use a transistor switch instead of the sparkplugs to ignite a gasoline-air voltage reaches the spark plug, the the points to interrupt the primary mixture is carried out by a process electricity arcs across the gap of the current. The transistor switches are which employs Faraday’s Law. sparkplug to ignite the fuel mixture. contained in a solid-state Ignition Control Module. Modern coil designs produce voltage pulses up in the neighborhood of 40,000 volts from POINT STYLE IGNITION SYSTEM the interruption of the 12-volt power supplied by the battery. COMMON IGNITION SYSTEM D ECHNOLOGICAL GENERATIONS STANDARD IGNITION COIL The earliest design of ignition coil was also referred to as the “Can Style” coil, based on the general shape of the unit itself. This system was widely used on nearly all auto- motive makes and models with point style and electronic ignition systems. This was the primary ignition system from 1910 through 1985. Can style ignition systems operated on a 12V supply and worked in collaboration with a distributor system. The igni- tion coil had a positive and negative post that connected to the battery. ELECTRONIC IGNITION SYSTEM (CDI) Then, it had a spark plug wire that made the contact between the igni- tion coil and the distributor cap. G.M. HEI IGNITION COIL Through advancements in auto- motive technology, General Motors introduced the High Energy Ignition (HEI) system in 1969. GM’s HEI systems worked in collaboration with a distributor system like the can style systems (or standard ignition systems), but without the need for a spark plug wire going from the coil to the distributor. HEI coils have 2 wires During the mid-80’s, automotive plug wire to make the connection protruding from them with terminals manufacturers had continued to de- between the coil and spark plug. on the end that clip into the inside velop more efficient engines, which The benefit to this design is the of the distributor cap to another wire required more efficient ignition sys- deletion of the distributor, helping to harness that helps to make the con- tems. The coil pack ignition design improve engine bay efficiency and nection between coil and distributor. was introduced to remove the me- allowing the coil pack to be strate- This design for GM helped reduce chanical connection from the engine gically positioned on the vehicle. engine bay clutter by removing the to the coil via the distributor. Without external coil and incorporating it as the need of the distributor, these COIL ON PLUG IGNITION part of the distributor cap, as well as coil packs simply require spark plug SYSTEM (COP) reduced an additional current path by wires to be routed from the coil pack The 1990’s represented many removing the extra spark plug wire to the spark plug. On some GM industry changes to create more used in the standard ignition setup models, they are referred to coil near fuel-efficient vehicles. While much between coil and distributor. plug, where it’s a single coil for each of this is obtained in other depart- IGNITION COIL PACK cylinder but still requires a spark ments, such as weight reduction, For more information, visit www.walkerproducts.com or 844-252-0114. smaller engine displacements, and timing advance for the next firing Advanced features of Ion Sense so forth, the fuel-efficiency can be sequence. These COP systems are Subsystems, such as compensation greatly improved upon through the capable of inducing over 50,000 of combustion due to fuel variation, ignition and timing of the engine. volts if required (dictated by the are also available to help reduce The coil on plug ignition system was required ionization current). cold-start HC tailpipe emissions. developed to be the most efficient Delphi’s Ionization Current method for spark production in the Sensing Ignition Subsystem (Ion IGNITION COIL MATERIALS combustion process. As their name Sense) is a technology based on AND CONSTRUCTION implies, they sit directly on top of the principle that electrical current Potting Materials your engine, directly in contact with flow in an ionized gas (e.g. during The potting materials have changed the spark plug. There are several combustion) is proportional to the dramatically since the ignition coils factors to why COP ignition systems flame electrical conductivity. By inception; originally ignition coils are more efficient than their prede- placing a direct current bias on were paper insulated wiring coils cessors. Some of those reasons the spark plug electrodes, the mounted in wood or steel boxes. include the ability to replace indi- conductivity can be measured. Later the ignition coil was built into vidual coils as they fail, as opposed the familiar conical shape and filled to replacing an entire coil pack With Ion Sense technology, the and formed with a phenolic plastic because just one output failed. In conventional spark plug acts as potting material to protect it from addition, there is the added benefit an intrusive sensor in the cylinder vibration and heat. of no longer needing spark plug to obtain information about each The potting materials have wires, which reduces overall system combustion event with minimal changed from phenolic plastic, components and unnecessary elec- influence due to environmen- epoxies, urethane polymers, and trical resistance. tal conditions such as vibration, most recently to DuPont Rynite® mechanical noise, and tempera- and Thermx®. The materials may DELPHI IONIZATION CURRENT ture. Optimized individual cylinder look like the same black plastic, SENSING IGNITION SUBSYSTEM knock control helps increase engine but they have evolved dramatically. Some modern COP systems were efficiency and reduce fuel con- Some early ignition coils were oil further advanced by Delphi in 2012 sumption. Through this Ion Sense cooled (the windings were sub- to monitor Ionization current to technology, misfire detection is OBD merged in oil), which could leak determine a number of factors such II capable and provides very high and cause overheating and coil as misfire detection, knock detec- reliability and robustness compared failure; but all modern ignition coils tion, fuel compensation, and proper to many other detection methods. are now dry due to improvements For more information, visit www.walkerproducts.com or 844-252-0114. in core materials, coil winding copper coated aluminum wire. core made of ferromagnetic metal materials, and potting materials Originally the windings were insu- such as iron, or ferromagnetic com- that can withstand higher under lated with paper or cloth. Most pounds such as ferrites to concen- hood temperatures, vibration, modern coil windings are now trate the strength and increase the and higher secondary voltage. insulated with polyurethane or effect of magnetic fields produced polyamide enamel composites. by the electric current. Coil Winding Materials The presence of the magnetic Primary and secondary coil wind- Magnetic Cores core can increase the magnetic field ings use an insulated copper or All ignition coils have a magnetic of a coil by a factor of several thou- sand over what it would be without the core. CONCLUSION It is easy to see the advancements in technology throughout the years. As we continue to evolve the internal combustion engine to be more and more efficient, components such as ignition systems must also continue forward. Because there are so many variations of ignition coils in the automotive aftermarket today, Walker has committed to providing a full line of OE quality replacements for all makes and all models. Through quality, cov- erage, and support, Walker Prod- ucts can provide the necessary resources to grow your business.
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