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A to Z of Electricity: A Glossary of Ignition Terms

Ignition experts have a lot of weird jargon they throw around, expecting you to know what they're talking about. Well, next time you're stumped by their techno-babble, just look it up right here!

Ignition Coil

A type of induction coil or transformer. It generates a high-voltage pulse from a low-voltage source, allowing the spark to jump the plug gap. 

Coil Terminology

Ballast Resistor

A resistor in the primary ignition circuit that reduces the voltage across the points of a breaker points distributor (see below) after the engine is started. This prevents arcing and reduces wear on the points and other components. 

Coil-On-Plugs

An ignition configuration where each spark plug has it own coil mounted on top of it. 

Coil Pack

A collection of remote mount coils (see below), used in a distributorless ignition system. Typically, each coil in the pack powers one or two spark plugs. 

E-Core Coil

A type of coil in which the magnetic core is shaped like the letter "E", which creates a closed magnetic system for less electromagnetic interference.

High Energy Ignition (HEI)

A type of inductive ignition, developed by GM in the emissions-conscious 1970s, designed to better ignite lean air/fuel mixtures. It uses no ballast resistor, but has a magnetic pickup distributor with the coil on the cap and a module to regulate the amount of current on the primary side of the ignition. 

Potting

Also called encapsulation, this is a process in which electrical circuits are covered with a liquid resin, which is then cured. The circuits are thus protected from physical damage. 

Remote Mount Coil

An ignition configuration where the coil or coil pack is located away from the spark plugs. Also refers to a reconfigured HEI ignition, with the coil relocated off the distributor cap. 

Spark Duration

The length of time a spark exists. Longer sparks burn more of the air/fuel mixture, but multiple short sparks can achieve the same results. 

Turns Ratio

The ratio of secondary wire windings to primary wire windings around the core of the ignition coil. This is effectively the multiplier for the output voltage of the coil: for example, if you put 400V into a coil with a turn's ratio of 105:1, then the voltage sent to the plug gap is 400 x 105, or 42,000V. 

Distributor

A device that distributes the electric charge needed to generate ignition sparks, traditionally via a metal point that rotates around a sequence of contacts. The rotation of the distributor is synchronized to the rotation of the engine so that the charge is delivered to the right spark plug at the right time. 

Distributor & Timing Terminology

Alkyd

A type of polyester resin, commonly formulated for high dielectric strength for ignition components. 

Blueprinting

Blueprinted components are constructed like OE components, then further machined to tighter tolerances for maximum performance. 

Breaker Points Distributor

Commonly just called "points"; this traditional type of distributor has a metal point on a rotor inside, which is physically rotated by the engine. The rotor is surrounded by contacts (one for each cylinder). As the point spins and passes each contact, the current jumps across the tiny gap. Older distributors have a section below this, where a rotating cam trips a lever, opening the points, causing the coil to lose its ground and generate a high-voltage pulse. The constant arcing can cause pitting on the contacts, eventually wearing them out, and at high rpms, the rotating mass can start to wobble. Points were largely superseded by Hall-effect distributors in the 1970s. 

Distributorless Ignition

As seen in most modern engines, this type of ignition uses a computer and a crankshaft sensor to control spark timing and output levels. It's more reliable and more efficient than a mechanical distributor, but changing the ignition timing requires an electronic tuner. 

Electronic Distributor

Generally any distributor without breaker points (and the maintenance issues associated with them), but still mechanically connected to the rotating assembly. There are a couple of kinds: 

Hall-Effect Distributor

A sensor outside the rotor senses magnets rotating past on the rotor and triggers ignition pulses. Also called magnetic pickup or magnetic breakerless distributors. 

Optical Trigger Distributor

The engine spins a vaned rotor, which interrupts a beam of light (such as a laser, infrared beam, or an LED), which triggers the ignition pulse. 

Magneto

A magneto spins at high speeds to constantly generate lots of current and high duration sparks. They're primarily seen on high performance race vehicles, due to the high engine speeds needed to operate, but since they're largely self-sufficient, there's no need for a heavy 12V battery. This is an inductive ignition design, controlled through breaker points or electronic circuits to turn the current on and off. 

Rev Limiter

Engines can be seriously damaged by revving beyond their normal tolerances, such as when they become suddenly unloaded due to loss of traction, or the transmission shifts into the wrong gear. A rev limiter prevents the engine from revving beyond a pre-set limit by dropping spark to different cylinders. 

Shaft Wobble

When spun at high speeds, the tiniest imperfections in the shaft connecting the distributor to the engine can throw the shaft out of balance. This wobble can ruin ignition timing. 

Spark Plug and Plug Wire Terminology

Crossover

When the current from one ignition wire jumps over to another wire; usually the result of the insulation being of an insufficient dielectric strength to contain the voltage. 

Dielectric Strength

The ability of an insulator to withstand electromagnetic fields and not break down or fail to insulate. High-voltage ignition systems require insulation with a high dielectric strength.

Flashover

An unintended high voltage electrical discharge around an insulator, or arcing/sparking between adjacent conductors. 

Plug Gap

The gap on the end of a spark plug that the current must jump to create a spark and ignite the air-fuel mixture in the cylinder. If the gap is too narrow, the spark will be small, resulting in difficult starting, poor fuel economy, and high exhaust emissions levels. Too wide, and the spark may not be able to make the jump, resulting in misfires.

Radio Frequency Interference (RFI)

Also called electromagnetic interference (EMI), this is the radiation created by rapidly-changing signals in electrical circuits which can interfere with other electrical operations, such as radio signal reception or computer functions.

Solid Core Wires

Plug wires with a core of solid metal. These are ideal for magneto applications; they're sufficient for stock or mildly modified vehicles, but can create RFI at higher voltages, disrupting on-board electronics. 

Spiral Core Wires

Plug wires with the conductive metal wrapped around an insulator, which helps suppress RFI. 

Inductive vs. Capacitive Discharge (CD) Ignitions 

What Do They Do?

An ignition system combusts the air/fuel mixture in a compressed engine cylinder by creating an electrical discharge or "spark" across the air gap on the spark plug. To do so requires high electrical voltage, as the compressed air makes it harder for the current to jump the air gap (a typical high performance street engine requires 8,000-12,000 volts to ignite the mixture). As cylinder pressures rise—as in high performance racing engines—the voltage must increase to compensate. 

Inductive ignitions trigger (usually with breaker points or Hall-effect sensors) an induction coil to generate a high-voltage pulse from a low-voltage source. Stock vehicle inductive ignitions are simple in construction and produce a long-lasting spark, but at higher rpms the coil does not have enough time to fully charge, reducing voltage and current output, and hindering performance (this is called "high-end drop-off"). Technically, magnetos are also a type of inductive ignition, but because they must spin at a high rate of speed, they are best used in high performance racing vehicles.

Capacitive discharge (CD) ignitions use a capacitor and a control box to apply hundreds of volts to the coil, which is transformed into tens of thousands of volts. Because the CD spark is shorter in duration than a regular inductive ignition spark, most CD systems use analog or digital controls designed to fire 8 to 12 sparks per combustion cycle at low rpms, ramping down to a single spark per cycle at around 3,000 rpm. CD ignitions perform more consistently than inductive systems at higher rpms, and are virtually required by turbocharged, supercharged, or nitrous-injected engines, due to the high cylinder pressures.

About the Author

Why did Rev Wright decide to make speeches at a time when Obama might have liked silence?

This didn't make any sense to me. If Obama and Rev Wright are supposedly so tight, why would he betray Obama by going public with MORE speeches taking up HOURS of air time on the 3 major TV stations? Or was he "set up" by a Clinton supporter? According to LA Times, the person who arranged for Wright to speak at the National Press Club was Barbara Reynolds a solid Clinton supporter. Sound fishy??

Read these:

http://latimesblogs.latimes.com/washington/2008/04/wrightsetup.html

http://tpmcafe.talkingpointsmemo.com/talk/2008/05/ardent-hillary-backer-organize.php

Was this another Clinton tactic?
Before you comment, please read the link. There is no such thing as a coincidence.

Someone once said, "Everything in politics is planned, everything."

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