Got spark – got fuel. When you have them both, you’re going to have a combustion event of some sort, but there’s a lot more to it when it comes to race cars. When that spark occurs in the combustion chamber, it’s energy. Timing, and the right mix of air and fuel, are the main ingredients that determine the outcome of the combustion process within the cylinder, and the resulting force to push the piston down.
Of course, we’re simplifying matters, as there are still many other variables, including compression ratios, combustion chamber and piston design, valve timing, fuel quality, and more. You can have the ideal mix of air and fuel along with perfect delivery of this mixture into the cylinder, but if the ignition system isn’t up to snuff – or not set up properly – that perfect fuel mixture isn’t going to do you much good. (Conversely, all the spark voltage in the world isn’t going to be worth squat without the fuel – but for this story, we’re talking about the spark). Within this article, you’ll see products from Edelbrock, FAST, Mallory, MSD, and Performance Distributors.
The ignition system of a race car is one area that can be improved and easily tuned to help your engine achieve peak performance. Remember, the ignition is responsible for the outcome of many systems working together on your engine. When you improve other systems, such as better flowing heads or intake, or add an improved cam profile, the ignition plays an important role in delivering the most from these engine updates.
Scroll through any website or parts catalog, and you’ll note there are a lot of ignition components available designed to improve a racing-ignition system, such as CD controls, advance kits, low-resistance wires, distributor modules, high-output coils, and others. In fact, it can become a little overwhelming when you first start researching what you need for your race car. So, where do you start?
Before you buy any ignition part for your dirt car, you need to dive into your rule book to see what’s legal in your class. In dirt track racing, many classes limit ignition modifications, or mandate certain components to try to keep everyone on the same level (with varying results in many cases). Once you know what your limits or opportunities are in the world of spark, you’ll be set to go.
First, however, lets take a closer look at the components that make up your engine’s ignition system, starting with the hardest working ignition component – the distributor.
The distributor has a variety of responsibilities: trigger the high-voltage circuit at the coil, distribute the spark to each cylinder, alter the ignition timing to compensate for load and RPM, and in most applications, turn the oil pump. By making the move to a higher-quality aftermarket distributor, you ensure that each task is handled precisely.
It’s important to note that a distributor hasn’t been used on a domestic engine application in about 20 years. But on the dirt track, they’re still the number one ignition. Coil-per-cylinder engines are on the rise, but for this article, we’re sticking with a distributor-triggered ignition.
Most aftermarket distributors use an electronic trigger, such as a magnetic pickup, light emitting diode, or Hall-effect trigger. These are accurate, maintenance-free, and very reliable. These pickups provide the trigger signal to the coil or aftermarket ignition box to fire the high-voltage spark. The accuracy and endurance of the trigger pickup are extremely important to performance on the track.
One of the most popular distributors used in dirt track racing is the HEI distributor. GM offered this High Energy Ignition distributor on all of its brands in the early ‘70s, as an upgrade from breaker points. The distributor incorporated an electronic trigger assembly for maintenance-free accuracy, plus, the coil was built into the top of the distributor. It’s a complete ignition.
Forty years later, the HEI is still the most popular distributor in dirt track racing. Ignition manufacturers have done a great job building higher-output ignition modules and coils, as well as stronger distributors to handle the higher RPM use of racing. We’ll touch more on the latest HEI offerings in part two of our ignition story.
The coil is responsible for taking in 12-14 volts from the battery and stepping it up to a 1000 volts, creating 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 (primary and secondary). Also, an iron core strengthens the magnetic field created as the battery current flows through the primary windings.
The primary windings (wrapping of wire), are usually several-hundred turns of a heavier wire. The secondary windings are a finer material with several-thousand wraps. (This gives you the turns-ratio winding that you see in coil specifications such as 100:1 or 70:1 which is another story in itself.)
When the switching device of the distributor opens – whether it be breaker points or an electronic trigger source – it causes the current flow through the primary windings to stop, forcing 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 spark plug terminal to the distributor.
Spark Plug Wires
Of course, the ignition system is only as good as the sum of its parts. If one area is neglected, spark output suffers. Before you even think about upping the output of the ignition, make sure to have a good quality set of spark plug wires.
There is an abundance of performance spark plug wires available from the aftermarket, and you’ll want to make sure to use a quality suppression wire. A plug wire must be able to suppress the Electro Magnetic Interference (EMI) that occurs as electricity travels through the wire. Today, there are a number of low-resistance wires available that have high-EMI suppression capabilities. Also, take into account the durability of the outer sleeve, the boots, and the terminals used with the wires.
Depending on what class you race, you may see a lot of Capacitive Discharge (CD) ignition controls in the pits. A CD ignition is capable of producing full-power spark throughout the engine’s entire RPM range with no fear of a weak spark at the top-end of the revs, which is common on factory-style inductive ignitions.
A CD ignition draws its voltage supply directly from the battery, and uses a custom wound transformer to step up this voltage to over 500 volts or more. This voltage is stored at full strength in the ignition’s capacitor, which is much more efficient than a coil, resulting in full-power spark from idle to redline and above.
Another benefit of most CD ignitions is that they produce a series of sparks at lower RPM. This spark series occurs from initial engine cranking to about 3,000 rpm, and is very beneficial for quick starts and cleaning up the idle. But for racing, the high-energy sparks delivered near redline are where CD ignitions really shine.
With the basics covered, we will do a deeper dive into the different systems in part two of this series. Our major goal is to show the garage mechanics what makes these systems tick. We will cover basic installation tips and tricks, building a system to the rules, and how to decide what is best for your application. We might even have a pro tip or two for those looking to get a little extra from their ignition.