How It Works - Pertronix Ignition Systems

Don Lindfors of Pertronix Performance Products Serves Up an Electrifying Education

Stephen Kim Feb 26, 2014 0 Comment(s)
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What's the Point?

Although points-style ignition systems have served the automotive community faithfully for many years, they have numerous shortcomings. The most obvious is that regardless of whether the subject at hand is a performance vehicle or a grocery getter, ignition points wear out. "The points operate mechanically with a rubbing block that rubs on a small cam in the distributor. This rubbing block wears, which changes the timing and the point gap, altering both the performance and the amount of spark available," Don explains. A points system also requires a condenser, which prevents mini-arcing when the points open and close. Without the condenser, this mini arcing would not only wear the points out faster, but it could also cause the primary winding to collapse across the points. This would weaken the spark, so the condenser absorbs the initial shock of the primary winding and delays it just enough for the energy to travel to the secondary windings, creating spark at the spark plugs. In essence, the condenser is a capacitor that wears out from absorbing all this energy millions of times.

Much like the valvetrain in an engine, the mechanical components that comprise a points system are prone to float and bounce. As the points open and close, they rely on a flat spring to keep them in contact with the cam. This keeps them opening and closing at the right time and with relative precision. As rpm increases, however, they reach the limits of the spring, resulting in float and bounce. "Float is where the spring can't keep up, and the points don't close all the way, causing misfires. Bounce is when the spring is over-stressed and the rapid opening and closing cycles causes the points to bounce back open, creating more misfires as the coil is rising and collapsing at the wrong times," says Don. "To combat this, the PerTronix Ignitor system uses a Hall Effect sensor that replaces the troublesome factory breaking points. The sensor is essentially an electronic switch not limited by rpm or mechanical shortcomings. There are no parts to wear out, so in a healthy electrical system, the Ignitor can operate indefinitely. By not having the problems of points arcing and condenser failings, combined with improved control over the breaking of the current to create the collapse of the magnetic field, a stronger spark is the result. A strong spark is the product of the magnetic field collapsing both quickly and powerfully, and that is something that a Hall Effect sensor does much better than a points system."

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Ignitor II and III

"PerTronix's original Ignitor system, which has been on the market now for 40-plus years, is a basic Hall Effect sensor that replaces the mechanical switching of points to an electronic switching system. In contrast, the Ignitor II has built-in reverse polarity protection and over-current protection that shuts down the system, preventing component damage if the key is left on without the engine running. Additionally, the Ignitor II units sense the coil current level and use a powerful micro controller to adjust the dwell through PerTronix's patented Adaptive Dwell technology. The Ignitor III takes the features of the Ignitor II even further with the addition of a multi-spark feature and a digital rev-limiter built into the module. At PerTronix, we call this ignition box performance without the box. Additionally, the Ignitor II has a built-in four-degree spark retard during start up to ease the start-up stress in high-compression engines."

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Multiple Sparks

Sometimes, one spark isn't enough, which is why many aftermarket ignition systems feature multiple spark technology. "Introducing multiple sparks ensure that the all of the air/fuel mixture inside the combustion chamber gets burned for maximum efficiency and peak power. Unburned fuel is wasted energy that can also contribute to decreased power, higher emissions, and hotter running temperatures," says Don. "Unlike most multiple-spark units on the market, the PerTronix Second Strike ignition box and Ignitor III module deliver multi-spark operation from idle through redline, not cutting out at lower rpm. This is done through complex electronics and specialty low-resistance ignition coils that allow for the rapid charge time required to accomplish multi-spark performance through a broad rpm range."

Adaptive Dwell Technology

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"The Ignitor II and III both utilize adaptive dwell technology. To understand what is it and how it works, we first need to define dwell and how it can impact performance. Dwell is the time that the points or the electronic module in an ignition system are closed, and the coil is charging. Standard ignition systems have a fixed dwell angle, meaning that the coil is charged for a fixed period of time during the engine cycle. As rpm increases, that dwell angle has less and less time, so the coil gets charged less per spark event, resulting in a weaker spark. At high engine speeds, a weak spark often becomes the limiting factor for performance and even causes misfires.

"Using Adaptive Dwell Technology, the Ignitor II and III sense the time it takes the coil to charge up to peak current. They use this data to schedule the coil turn-on time so that peak current level is reached just prior to spark for maximum energy without heat buildup, increasing coil and module life. This way they can adapt to any coil that they are connected to. When connected to a stock coil, adaptive dwell maximizes ignition system efficiency, but the real advantage comes when it is used in conjunction with a low-resistance PerTronix Flamethrower II or III coil. Low-resistance coils charge up quickly, and would overcharge and burn up at low rpm in a stock system. The adaptive dwell of the Ignitor II and III keeps the charge time in check at low speeds, and the fast charge time of the Flamethrower II and III coils keeps the spark energy high, much further up the rpm range. The result is a system that works efficiently at low rpm and delivers full spark energy at high rpm."

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