MSD's Electronic Ignition System - Going Digital

A new wave in high-tech ignition systems

Wayne Scraba Mar 1, 2001 0 Comment(s)
Sucp_0012_01_z 2000_sema_performance_parts Digital_system 1/13

So you're wondering what's the big deal with "digital," are you? Unless you've been hiding under a rock for the past decade, almost everything you hear about is new, improved, and digital. The "old stuff" was analog. And guess what when it comes to adding this technology to your hot ride, there's more available than just CD players. One of the most recent areas to go digital is electronic-ignition systems. So what does it mean, and why are digital systems better than older analog electronics? Before looking at digital ignition systems in particular, let's take a look at the differences between analog and digital circuits. Here's the technical definition of both (drawn from an electronics dictionary):

Digital Circuit: This is a circuit in which the output currents or voltages are interpreted as having one of several (often two) values, depending on which of a corresponding number of ranges they fall into. Such circuits implement logical operations or operations on representations of discrete numbers, often in binary form.

Analog Circuit: This is a circuit in which the output voltage and current values are considered significant over a continuum. Analog circuits may be used for such purposes as amplifying signals.

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One thing you'll notice about today's crop of digital ignition systems is the physical size. While this MSD Digital-6 Plus system is slightly longer (roughly 1/2 inch) than its analog counterparts, it offers a number of internal features, which would require add-on accessories in older systems.

Proportionate Technologies?
There's more to consider than a simple definition, though: When you take a look at a computer, you'll find that it is basically a device capable of performing a series of arithmetic, or logical, operations. A computer is distinguished from an adding machine (a good example is a simple hand-held electronic calculator or even an ancient abacus) by being able to store a computer program (this allows it to repeat operations and make "logical" decisions) and to store and retrieve data without intervention from you.

Technically speaking, computers are classified as analog or digital. An analog computer operates on continuously varying data. Meanwhile, a digital computer (such as today's common PC) performs operations on what is called "discrete data." An analog computer represents data as physical quantities and operates on the data by manipulating the quantities. In a complex analog computer, continuously varying data is converted into varying electrical quantities and the relationship of the data is determined by establishing an equivalent relationship, or "analog," among the electrical quantities.

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When you compare an analog ignition to a digital system, it's easy to see that the new digital ignitions are physically smaller, and can have more internal features. Since there are so many good things associated with digital ignitions, does this mean analog systems are obsolete? Hardly. There are plenty of high-powered, sophisticated ignition systems out there that get the job done (some with flame-thrower-like spark capability). The MSD 7AL3 on the right is one of them.

While analog computers are commonly found in such forms as electrical watt-hour meters, they largely have become obsolete for general-purpose mathematical computations and data storage thanks to digital computers. Inside a digital computer, data is expressed in binary notation (or "numeration"). Essentially, this is a series of on-off conditions that represent the digits 1 and 0. A series of eight consecutive binary digits, or bits, is called a byte and allows 256 on-off combinations. Each byte can represent one of up to 256 alphanumeric characters. Mathematics and comparative operations can be performed on data represented in this way and the result stored for later use. Digital computers are used for things like desktop publishing, scientific research, data-processing...and now, race car ignition systems.

A Less Intense Explanation...
As you can see, the definitions of analog and digital are definitely hard on the brain, and if you're not into computers or electronics, they can certainly tend to be geek-speak. Here's the simple answer: The best way to understand the differences between digital and analog is to think of the differences between a good old-fashioned wristwatch with a sweep second hand and the LCD readout on something like your VCR. Both display time, but the wristwatch is constantly varying. Simply stated, as the second hand sweeps around the face of the wristwatch, the information that is displayed is constantly changing.

Next, regarding the clock on your VCR, it's really presenting the same information, but in what's called a "discrete demonstration." In other words, it displays one piece of information at a time.

An analog system is like the good old-fashioned wristwatch with a second hand. It attempts to recreate the information as it actually happens. The digital system takes the information and represents it as a series of changes, or "bits," that are represented in code by zeros and ones.

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