A Performance Automotive Ignition System Overview
The ignition system, much like the fuel, brake or suspension systems, is comprised of several different components that all must work in concert to complete their goal effectively. In the case of the ignition system, that goal is to create a high-voltage spark at the exact right moment during the compression stroke of an internal combustion engine – and to repeat the process millions of times.
The ignition system is one area that can easily be improved by selecting the right components to match your engine’s needs and your performance goals. However, when you wade through all of the product options available through a hot rod or speed shop, the choices can get overwhelming – CD ignitions, low-resistance wires, HEIs, high-voltage coils of all shapes and sizes. Where do you start and what exactly do these parts do?
We’re here to help guide you through the ignition system with a quick overview of the components and their operation so you can make the right choice for your hot rod or custom project.
The distributor is probably the hardest working component of the ignition system. It’s responsible for triggering the high voltage from the coil, getting the spark to each cylinder via the rotor and cap terminals, and in most cases, alters the ignition timing. (Not to mention drives the oil pump!) Having a high-quality, well-prepped distributor ensures that each task is handled precisely.
Unless you’re building an era-correct vintage hot rod, there’s just no reason to use an old distributor with mechanical breaker points. Even then, there’s modern electronics that you can easily install under the cap that will take the place of points and even improve the ignition output. Most aftermarket distributors use a maintenance-free electronic trigger such as a magnetic pickup, light emitting diode, or Hall-effect switch and have smooth, easy-to-adjust centrifugal advance assemblies – a win-win combination.
One of the most popular distributors used on street rods and street machines through the years has been the GM HEI. This fully electronic distributor was introduced in the early-’70s and is a favorite for a couple different reasons. First, the coil is integrated into the cap assembly, so everything is included in one unit. Second, the wiring is easy – only one switched 12-volt source is required.
The downside of the HEI is its girth, which can limit its use in tight engine compartments. An alternative is a ready-to-run distributor such as those from MSD, Pertronix and other companies. These distributors are the same diameter as GM points models, yet are fully electronic. Another choice is the Mallory Uni-Lite, which is even smaller in diameter and maintenance-free.
The coil is responsible for taking in 12-14 volts from the battery and stepping it up to thousands of volts to create a spark that is capable of jumping across the gap of the spark plug to ignite the air/fuel mixture. To accomplish this feat, the coil is made up of two series of windings, the primary and secondary, along with an iron core to strengthen the magnetic field that is created as the battery current flows through the primary windings.
To summarize a coil’s operation, the primary windings are usually several hundred turns of a heavier wire while the secondary windings are a finer material with several thousand windings. When the switching device triggers the coil, current flowing through the primary windings stops, which forces the magnetic field to collapse across to the secondary windings. This induces a very high voltage which is sent out of the coil through the secondary (spark plug) terminal to the distributor.
The coil of your ignition system should be a quality model with high voltage output capabilities. Most manufacturers design their coils to operate best with their ignition or distributor, so it is usually good to keep the system matched.
Spark Plug Wires
Before you even think about upping the output of your ignition system, make sure to have a good quality set of spark plug wires. Wires will actually wear over time and can easily burn. If a boot or terminal fails, an engine miss will develop, so it’s important to inspect wires during routine maintenance.
There’s an abundance of performance spark plug wires available from the aftermarket. Most are good quality plug wires and feature lower resistance which improves the spark delivery to the plugs. It is important to use a spiral wound, or suppression wire, as this style wire helps prevent electrical interference with other vehicle electronics. Steer clear of solid-core wires as they have no way of suppressing electrical interference which can lead to troubles. Also look for wires with a hearty sleeve, quality terminals and high heat boots.
As for the spark plugs, there are oodles of models to choose from, but you need to consider the ignition system you’re using. If you’re running a high-output CD ignition, steer clear of platinum style plugs as they don’t dissipate the extra heat very well. For mild or stock systems, standard plugs will be just fine, or you can pay the extra bucks for the longer-lasting designer plugs if you prefer.
You see a lot of CD ignition systems, such as an MSD 6AL, FAST 6A, or the Mallory Hyfire, under the hoods of cars at Goodguys events, and for good reason. These units are Capacitive Discharge Ignitions (CDI) and are capable of producing a much higher voltage spark. Another benefit is their ability to multi-fire the same plug at lower rpm. These multiple sparks can aid in the idle quality, starting, and throttle response of your hot rod.
For those of you running a later-model engine, there’s not much to your ignition system other than eight coils and for LS engines, there’s a short plug wire. The benefit of having a coil for each cylinder is better spark control and cylinder timing through the ECU of the drivetrain.
The coils from the OEMs are fairly stout and can handle quite a bit of power, but when you’re making serious power, or simply need to replace a coil or two, the aftermarket offers coils with improved output and capabilities. Most ignition companies offer coils for LS, Coyotes and even the dual-plug Hemis.
Photos courtesy of the Manufacturers