We understand the principles, but whatever actually happens “in there” is to some degree, confined to our imaginations. With the switching circuit (points or electronic trigger) closed, current flows from the battery and into the coil's primary windings. Channel D: Coil amplifier earth It has an iron core with fairly thick wire (primary winding) wrapped around it a few hundred times. This means that current moves in one direction, from the positive battery terminal to the negative battery terminal. 5. Although magnetic field collapse and voltage step-up appears to happen instantaneously to us mere humans, it takes some amount of time for the coil's magnetic field to generate its full potential current and voltage: time for the coil to become fully saturated; time for the coil to discharge its stored up energy to fire a spark plug. The output voltage will be 100 times greater than the input voltage. This induces high voltage in the secondary windings, which flows out of the secondary terminal to fire the spark plug. Either way, somewhere in the 4-6 amp range while the car is running. 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). When the coil's primary circuit is switched on, the voltage drops slightly, and as the current in the circuit increases to the target of 11 amps, the voltage drops accordingly. (For a discussion of capacitive discharge vs. traditional pure inductive ignition systems, see: "Inductive vs. Capacitive Discharge Ignition Systems. More heat, more resistance. You cannot operate a car smoothly without delivering high voltage to the spark plugs to ignite the air-fuel mixture. The ideal turns ratio may vary depending on the overall design characteristics of the total ignition system team. A lot of the older systems used 12 volts to the coil when the ignition switch was in the start position than when released to the on position the resistor alowed reduced voltage to the coil. It’s the part of a car’s ignition system that takes the battery’s 12-volt output (called low-tension current) and transforms it into as much as 45,000 volts (called high-tension current) before then supplying it to the engine’s spark plugs. The role of the ignition coil is to multiply battery voltage into high voltage. The average vehicle ignition coil puts out 20,000 to 30,000 volts, and coils used in racing applications are capable of 50,000 or more volts at a constant rate. MSD has a whole series of Blaster 2 and 3 cannister-type ignition coils that can replace stock coils used in various OE ignition systems. Renault Clio at 30: Highs and lows of a hot-hatch hero, Hidden Bugatti may fetch over $9 million at auction, Chip Foose reimagines the iconic Jaguar E-type, Chip Foose reinvents the 1966 Ford Bronco with street-savvy style, Take a look inside the world of vintage Ferrari V-12 engines, Wrenchin’ Wednesday: Efficient, no-mess grease packing, Jeep Grand Wagoneer LS swap: Project accomplished, lessons learned, Watch this 56-mile Buick Grand National get a much-needed pampering, Reconfiguring a novelty ignition system requires a novel solution. The ignition coil has a resistor in series with it so you should measure around 9V when the points are closed. When the points open, the flow of primary current stops and the magnetic field collapses. Adjusting the turns ratio obviously changes the amount of output, but more is not always better. See How Car Engines Work or How Two-Stroke Engines Work for details. However, more voltage does not always mean better in the world of ignition coils. At low rpm, 30 degrees of coil dwell time can be 2 or 3 times longer than needed, resulting in excess ignition system heat buildup and unnecessary alternator power consumption. However, if resistance is too low, the higher current could damage the distributor's points or electronic trigger. Sometimes the thin lacquer insulation between the two windings deteriorates. In the case … A 100:1 turns ratio (typical of many coils on the market) means there are 100 secondary turn windings to every one primary turn. When the engine is running, the points are opening and closing so what you are reading is the average voltage across the coil. When teamed with a capacitor, the coil becomes a tuning device for the ignition system. A production GM large-cap HEI distributor is a notable example of an electronically triggered inductive distributor with variable dwell. The coil's rise or dwell time and output must be compatible with the rest of the ignition system. The resistor wire is in place. The voltage induced with each spin goes to the primary coil, which has about 75 turns. When you switch on the ignition and the breaker points are closed, current flows through the primary winding, creating a magnetic field. This is called “ignition timing.”, If your car uses a negative ground and you have a coil with primary and secondary terminals, the primary winding is connected to the terminal on the coil that is marked “+” or “Bat.” This is the terminal that receives voltage from the battery. The idea behind any ignition system is to generate an extremely high voltage -- on the order of 20,000 volts -- at exactly the right time. Resistance is futile: Coils with even the same turns ratio can still have varying amounts of resistance. All automobiles work on DC, or Direct Current. The duration of dwell can vary depending on the type of ignition system—30 degrees with most traditional points systems, but various electronic triggers can have (depending on the design) less dwell, more dwell, or even variable dwell. Dwell isn't swell. 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. If the ignition works properly with the good coil, you will know the original coil was bad. 1. Photo: MSD. Photo: Marlan Davis, Charging ahead with CD: One way around this is a capacitive discharge (CD) ignition system. I read that modern coils draw about 4 amps while the points are closed. The series resistor in the ignition circuit will not develope a voltage drop, so you do not loose any voltage. Most coil failures result from secondary winding defects. Fig. MSD has a whole series of Blaster 2 and 3 cannister-type ignition coils that can replace stock coils used in various OE ignition systems. It may require only 1,000 volts for it to ignite when the engine is idling and cylinder pressure is low, but then need 20,000 volts to climb a hill under full throttle. Just how does an ignition coil work to step up a battery's 12 volts (even less with a ballast resistor) to the tens of thousands of volts needed to fire the spark plugs? This is a sufficient voltage to produce arcs which jump an air gap of an inch or more. Some extremely high-output coils may only be used in short-duration drag racing, as compared with others optimized for long-duration oval track or an extended lifetime of street performance. All coils with metal housings can be tested for grounded windings by touching one probe of an inexpensive test light on the metal container and the other to the primary and high-tension terminals. The MSD ignition also produces a series of full power sparks through mid range rpm. With the ignition switch in the RUN mode. Many service manuals recommend temporarily substituting a known good coil for a suspected bad one. The coil will still need a minimum of 1.5 ohms of resistance, either internally such as the Flame - … To find out for sure, use a multimeter to check the voltage on the positive wire of the coil with the ignition on. They're also a good complement for MSD 6-series ignitions. If oil starts leaking out, it's a sign that the coil's days are numbered. Capacitors charge far more quickly than a coil, and the best of these systems can fully charge up to as high as 15,000 engine rpm. Either 12V across a 3-ohm primary coil or 6-9V across 1.5 ohms in a ballast coil. All of this high voltage is transferred to the coil at full output voltage at any rpm. Increasingly higher turns ratios affect other electronic properties such as resistance, reactance, and impedance. AMPERAGE is the limiting factor when the life expectancy of an ignition is the concern. When a current flows through a conductor, it generates a magnetic field around the conductor. The Stator is the plate holding all of the electrical coils of wire, which is used to power ON the ignition coil, bike’s lights, and battery charging circuits. In the example waveform, the voltage is about 14.0 volts. Coils can be tested with an ohmmeter (most coils will give a reading around 8,000 ohms) or with the small scope on a Sun machine. So that being the case, your 1.5 figure falls in line with the specs for the external resistors so it would seem to indicate your coil does have an internal resistor and therefore you would not need an external resistor. A "hot" coil runs...hotter: As coil output increases, so does its need to radiate heat. The supply voltage is stepped up to 520-535 volts by a custom transformer and is then stored in MSD’s efficient capacitors. The Ignitor™ lead (red wire) can go directly to the ignition switch or any other "switched" source on the fuse panel. Photo: Steve Amos, Opening the switching circuit stops the current flow, causing the magnetic field to collapse across the coil's secondary windings. Time waits for no mortal...or ignition coil. 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. It’s a Windings Road! According to Wired for Success author Randy Rundle, you would be well-advised to look in the back of hobby publications for companies that specialize in the restoration of lock-switch coils and other ignition parts. Why does an engine need one? IF it's about 8.5 volts, 4. A common automotive ignition coil can generate an output voltage on the order of 30,000 volts. Working on your own car always carries a level of risk. This new voltage is then routed to the distributor via the coil wire, which is just like the spark plug wires, only normally much shorter. This posed a dilemma for the ignition … The CD ignition draws voltage supply from the battery and steps up the voltage to 500 volts and higher, it then stores the voltage in the ignition’s capacitor. During this phase, the contact points are closed. The job of the magneto is to create a surge of high voltage (between 10,000 and 20,000 volts) at just the right moment during each revolution of the crankshaft. The final voltage is about 12 volts - 2 volts lower than the original voltage. The ignition coil transforms the battery’s voltage to a level that allows the spark plug to do its job. Your information will be collected and used in accordance with our  Privacy Policy. Too high a ratio causes secondary voltage to start decreasing. The OE GM/Delco module has a dwell predictor circuit that shortens lower-rpm dwell time to 15 degrees and lengthens it to as high as 40 degrees at high rpm. If it's 12 volts, it's not. Photo: Steve Amos. Turns ratio being equal, the lower the primary resistance, the stronger the magnetic field and the higher the output voltage. Picture here is for reference only. Failures and Fixes Most ignition coils are long lasting and reliable, but a weak coil you can be the cause of under-hood havoc. Turns for the better: The relationship between the coil's primary and secondary windings responsible for voltage step-up is termed the "turns ratio." For factory-type repair of a lock switch extension coil you may be able to find a swap meet vendor with a coil service package for your car. The starter does not have a solonoid so there will always be a reduced voltage going to the points, which is good. The high voltage is carried away from the coil by a high-tension cable that looks like a short piece of spark plug cable and runs to the distributor tower. Inductive vs. Capacitive Discharge Ignition Systems. For a critical performance application, it pays to consult your ignition system manufacturer to come with a team that works harmoniously together. Engineers refer to a coil's time-charge factor as "dwell," which is expressed in crankshaft degrees. Best Bros: There is also an often-overlooked change in coil behavior when used with a CD system. "). In the primary circuit, the 6 or 12-volt power supply charges the ignition coil. Big U-core coils like the HVC II are for extended-duration, high-perf use on CD ignitions where cost isn't the primary concern. © 2021 Hot Rod | MOTOR TREND GROUP, LLC. If your car uses a 12 volt battery, the 12 volts you put into the primary side of the coil will exit the secondary side as 30,000 volts! If you want a full 12 volts at the coil, and still maintain key control, use the original coil wire to trigger a relay, and have the switch side of the relay go straight to the battery. The greater the turns ratio, the greater the voltage step-up. ... You definitely do need it, or you will smoke your coil in short order by running it at high voltage (12+ volts) for long perods of time. This winding lies inside the magnetic field created when electricity goes through the primary winding. But at high rpm, 30 degrees isn't enough: The faster the crank spins (the higher the engine rpm), the less time available for recharging the coil. Support for these kinds of repairs is readily available. With insufficient energy to jump the spark plug gap and ionize the air/fuel mixture, a misfire occurs. With a 100:1 turns ratio and relatively low resistance, output is about 45,000 volts. To say it's a mite confusing is an understatement! Since a car ignition coil acts as a step-up transformer, the secondary coil has many more turns than the primary coil. An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system that transforms the battery's voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel. When a switch—the distributor points opening or an electronic trigger—interrupts the flow of battery current, the magnetic field collapses across the secondary windings. They're also a … These come with a full instruction sheet. A windings road: It all starts with the concepts of inductance and electromagnetism. When battery current flows into the primary windings, it produces a magnetic field. At some point a higher turns ratio becomes counterproductive. 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