MSD Ignition 101: Get Your Spark On

If you’ve been involved in hot rodding for any length of time, you’ll know these infamous letters: MSD. They stand for Multiple Spark Discharge, a patented design by MSD Ignition that fires your spark plug multiple times rather than the single time that the factory ignition does. We already took you on a complete tour of M-S-D ignition last year, showing you how they design, engineer, and manufacturer the most cutting edge ignition systems in the world. (See that video here.)

In this tech article and video, we’re going to educate you.. call it MSD Ignition 101. We’ll show you the differences between your STOCK ignition, and MSD Ignition. By the end of the tech article, you’ll not only know how MSD works but what it will do for YOUR Hot Rod!

Here is the video, and you can read the article below:

We all know the basics of how an engine works. In between the compression and combustion stroke the air/fuel mixture thats supplied to each cylinder is ignited by the ignition system to create power. The ignition event sounds simple enough, but as with any mechanical function it’s not always the case. Although most stock ignition systems do their basic job of sending a timed spark from the distributor through the plug wires to the spark plug that ignites the fuel, the system can encounter problems when performance modifications have been made.

What is MSD Multi-Spark?

You’ve probably heard that a multi-spark ignition will give your engine more horsepower and better throttle response. The big question is why. Let’s explain how an Multi-Spark Ignition works. With a stock ignition system, one small spark is all that is necessary to combust the mixture of oxygen & fuel in the cylinder. As you can see here, the stock ignition produces a single, weaker spark. Enough for a totally stock engine, but not optimized for performance.

When you begin to make performance upgrades to your engine, including free-flowing induction and exhaust, more air and fuel is required to maintain the correct air/fuel ratio. MSD’s ignition boxes feature Multiple Sparks at lower RPMS, along with a stronger, hotter, higher voltage spark to completely ignite the mixture. That’s easy to see in the video.

Now let’s discuss what MSD calls Capacitive Discharge.

Each spark an MSD ignition produces is an extremely high current spark. This is because MSD uses Capacitive discharge technology to produce a very high primary voltage. These high powered sparks ensure complete combustion of the fuel mixture at everything from idle to high racing RPM, producing more power. Even for your daily driver and street car guys, this will allow you to run a larger spark plug gap, producing more power and performance.

Street vs. Race Ignitions

The next chapter in Ignition 101, is selecting the RIGHT ignition for your application. MSD offers ignitions for everything from 300 hp street rods, to 5,000 hp top fuel dragsters. For example, MSD’s 6AL-2. It’s a digitally-controlled ignition that can produce up to 535 volts, has the multi-spark functions, and a built-in rev limiter and 2-step. With 135 millijoules of spark output, it’s great for serious street cars – but you’ll REALLY want something serioues – like this MSD Digital 7 – for a RACE CAR.

Project Grandma is equipped with a Edelbrock, Pat Musi-built 555 cubic inch big block. WITH NITROUS. At 1,100 hp, it’s combustion process features a whole bunch more air and fuel than a street car would have – and you need a correctly matched ignition to burn that mixture. This MSD Programmable Digital 7 Box has a number of upgrades that racers of all kinds – from Drag to Circle Track, want and need in a race box.

First, it features over 30% more spark energy, 190 millijoules per spark, than the 6-box. That will allow it to support engines even up to 2,000 horsepower. Second, it is programmable with MSD’s Pro Data-software, allowing custom timing adjustments, nitrous boost, and shift light activations, and even programmable rpm/time rev-limiting maps. Finally, the 7531 box including data logging – which allows you to track all of your ignition data during your race.

Quick Review of Points, Distributor, and Distributorless “MSD” Solutions

Now let’s say that you have a classic Muscle Car with points, or a newer Late Model that doesn’t even have a distributor… For our last Chapter of Ignition 101, we’re going to let you know that EVEN YOU can be helped.

The same type of technology found in the multi-spark ignition boxes is available for distributorless ignitions with coil-per-cylinder or coil-on-plug systems. MSD calls these systems the DIS, and Multi-Spark coil kits are even available for GM’s LS vehicles.

Finally, for you old-school points guys, any MSD ignition will hook right up, or you can switch to the MSD Ready to Run Distributor that include the MSD technology and the Distributor in one unit.

We hope you’ve learned something today about ignitions, multi-spark, and just how important THAT spark is to your engine’s performance. That’s it for Ignition 101, and we urge you to visit MSD’s website at if you want even more in depth information!

MSD Ignition Boxes: Quick Review

Below is a Quick Review of some of the MSD Ignition Boxes and Components on the market. Use this guide to pick the right MSD components for your vehicle:

MSD Digital 6 Plus

MSD has recently added a new high tech weapon to the line-up, the MSD Digital 6 Plus. This digital ignition control box is loaded with features that put you in control of your ignition. MSD’s digital operation uses a high speed RISC microcontroller to control the ignitions output while constantly analyzing the various inputs such as supply voltage, trigger signals and rpm. The high speed controller can make extremely quick compensations to the output voltage, multiple spark series, timing and rpm limits while maintaining accurate timing signals to within 1 degree and 1 percent of the rpm limits

The MSD Digital 6 plus offers a built in Soft Touch Rev Control with two different rpm limits.The Soft Touch circuitry provides a smooth and accurate rev limit by dropping the spark to individual cylinders. It produces a load-free rev limit that is within 1 percent of the selected rpm. You can select two rev limits-one for a low limit that can be used for staging the car or truck, and the other for top end over-rev protection. Both rpm limits are externally adjustable in 100 rpm increments and adjusted by easy to use rotary switches so there is no need to carry along extra chips.

A single stage retard step that can be activated when 12 volts are applied. This is great for nitrous applications. The retard will remain until the 12 volts are removed. This retard step can be connected to a nitrous solenoid activation wire or micro switch on the shifter. The retard is adjustable from 0 to 9.9 degrees in 1/10 degree increments.

MSD Programmable Digital 6AL-2

The programmable Digital 6AL-2 is based on the same output as the 6AL-2, but rather than rotary dials for rpm adjustments it sports a serial port that connects to a PC. Once you load MSD’s Windows based software on your PC, you’re ready to start mapping and programming. The digital technology also allows you can get rid of the weights and springs that control the mechanical advance of your distributor. Lock it out and create a timing curve that allows you to manipulate the timing down to tenth of a degree increments every 100 rpm. The advantage is precise timing control, with the ability to ramp the timing in or retard it at exactly the rpm that you want it to move.

Another great feature is for the forced induction fans. The ignition features a timing curve based on boost so you can map out a timing curve based on boost pressure. The feature that most boosted drivers will enoy is the ability to pull timing out during the holeshot – and ramp it back in during the run. Since many cars have more power than traction capabilities, being able to soften the power at the first section of the run can help reduce the tire shake off the line.

There are also three different rpm limits that can be set in 100-rpm increments; one for the burnout, one for the holeshot and a top end limit for overrev protection. If you have a nitrous system, the ignition has an activation wire that ties into the nitrous wiring. When the nitrous is activated, the timing can be retarded instantly!

Digital-7 Plus Ignition Control

For racers that don’t need a lot of programming options, the Digital-7 Plus Ignition is a great choice. State-of-the art technology allows the 7 Plus to produce more power while using less current. The CD circuits combined with an IGBT Coil driver deliver 520 – 535 volts to the primary side of the coil with up to 190 millijoules of energy at any rpm. Below 3,300 there is of course MSD’s powerful series of multiple sparks, rather than a single spark. This spark series burns in the cylinder for over 20° of crankshaft rotation resulting in improved combustion and increased power. The Digital-7 Plus provides racers with two smooth rev limits, one for top end overrev protection and another to activate with a clutch or transbrake switch for use on the starting line. Both are adjustable with rotary dials in 100 rpm increments from 2,000 – 9,900 rpm with a maximum of 12,500 rpm. For nitrous applications or for racers looking for a little more mph, there is a single stage retard circuit that is adjustable up to 9.9°. Next to the rotary dials there is an LED that will verify that the ignition is receiving a trigger signal and will also warn you if there is problem with the supply voltage.

The Digital-7 Plus incorporates proficient EMI filter components to keep inputs and signals free from electrical interference. Combined with the fast microcontroller and a unique input feedback circuit, the ignition is well protected against EMI.

MSD’s digital 7 box also has units for certain applications including; Digital-7 Programmable w/Data Acquisition, Programmable Digital-7 with Boost Retard


The 7AL-2 has been a staple in the drag race community for years. From Super Stock to Comp it’s the ignition of choice for racers. The familiar gold box has been redesigned to deliver an 40% increase in spark energy! It also features a popular two-step rev control for staging and over rev protection. LEDs lights are used for troubleshooting the unit and a convenient terminal strip makes for easy wiring.


The MSD 7AL-3TM is based off the well proven MSD 7AL-2 Plus. It features a host of the most popular drag racing accessories. A built-in Three Step Rev Control provides three different rpm limits that can be used for the burnout, staging and top end overrev protection. There is also a Multi-Step Retard with four different modules that can be activated at different times. Four 0° modules and a 2°, 3° and 4° module are supplied. Many race engines with crank trigger systems or locked-out distributors will benefit from the 7AL-3’s built-in Start Retard option.

During cranking the Start Retard will retard the timing 25° allowing the engine to turn over easier. When the engine starts, the timing will automatically go back to its mechanical setting. One last option is an RPM Activated Switch that allows you to activate a solenoid or shift light at an adjustable rpm. When the engine hits the desired rpm the RAS circuit provides a ground to the component to activate it. Vibration mounts, wires and detailed instructions are supplied.


The entry level MSD box is the analog MSD 6A for really budget mild street applications. The MSD 6A is the base model of the capacitive multiple spark discharge 6 Series design. This ignition works on modified street machines, trucks or street rods. The powerful multiple sparks of the MSD 6A ensures complete combustion. Easier starting, improved throttle response, reduced plug fouling, more power and increased fuel economy are all benefits from the 6A’s high energy multiple spark strikes.

Unlike the stock-type inductive ignition systems, MSD ignitions incorporate capacitive discharge technology. The supply voltage is stepped up to 520-535 volts by a custom transformer and is then stored in MSD’s efficient capacitors. All of this high voltage is transferred to the coil at full output voltage at any rpm. The MSD ignition also produces a series of full power sparks through mid range rpm. This series of sparks ensures complete combustion of the fuel mixture resulting in greater power and performance.

Like all of the MSD 6 Series Ignitions, the 6A will work with virtually any vehicle as long as it has a 12-18 volt electrical system. It can be triggered using breaker points, a magnetic pick-up or the output of an electronic amplifier.


If you are a weekend warrior at the strip, the MSD 6AL ignition is a good starter box for saving that high dollar engine. 6AL shares the same circuitry of the 6A with the addition of a built-in adjustable rev limiter. The combination of powerful sparks with the safety of a Soft Touch Rev Control is what makes the 6AL a popular ignition box for entry level drag racers.

MSD developed the Soft Touch rev control to prevent overrev damage to the motor in the event of a missed shift or parts failure. The rpm limit is adjustable in 100 rpm increments with MSD’s plug-in modules. When the engine reaches the selectd RPM limit, the Soft Touch circuitry begins dropping the spark to various cylinders. On the next cycle, these plugs are fired again to prevent fuel from loading up in the cylinder. The result is a smooth and accurate RPM limiting action without backfires or blowbacks through the carburetor.

MSD Distributors

In addition to ignitions, MSD has a line of distributors for most popular applications. Their Ready to Run, HEI and E-Curve distributors are great for street applications. These distributors have a built-in module and provide more than enough spark output for street/strip applications.

For the racer, the MSD Billet and Pro-Billet Distributors are the finest performance and racing distributors available. Every feature is designed to provide the best in performance and endurance to top off your ignition system.

Like the multiple spark, CD ignition, MSD was the first to introduce a distributor housing machined from a billet of aluminum. MSD uses state-of-the-art Computerized Numerical Controlled (CNC) mills and lathes to create each housing. This procedure produces a flawless, lightweight distributor housing that is accurate to within 0.001″.

The complete line of MSD Distributors uses a polished steel shaft that receives a QPQ, or Tuftride coating. This process produces a durable finish that reduces friction and resists corrosion. To accurately guide this shaft, MSD uses a sealed ball bearing located at the top of the housing. At the bottom of the housing, an extra long sintered bushing controls the shaft. This combination keeps the shaft spinning smooth and accurately throughout 10,000+ rpm.

All of the MSD Distributors (except crank trigger models) use a high output magnetic pickup to trigger the ignition system . This pickup is completely maintenance-free requiring no adjustment ever. The pickup is mounted to the base of the distributor housing and plugs directly into your MSD Ignition Control. A trigger signal is created as a precision made reluctor (attached to the shaft) passes by. The reluctor has a “paddle” for each cylinder and when the paddle passes the pickup, a signal is created.

One of the most important features of the MSD Distributors is the adjustable mechanical advance assembly. The advance assembly allows you to accurately modify the advance curve to match your specific application. To start with, the advance plate is stamped and machined from chrome moly . Weight pins are then staked in and tig welded in place. This assembly, along with the weights, then receive a corrosion resistant QPQ coating. Nylon weight pads are installed under the weights to ensure smooth movement as the weights are pushed out from centrifugal force to advance the timing. The advance assembly is mounted on top of every MSD Distributor making adjustments a breeze. A variety of advance springs and stop bushings are supplied with each distributor giving you the ability to set up to 24 different curves.

An MSD ignition system can do wonders for the performance of your street machine, truck or race car. The factory ignition system will do fine with a bone-stock engine, but as soon as you start adding performance parts, an MSD ignition system is a given to keep up with the extra spark demands needed to feed intakes, heads and cam. If you plan to go the nitrous or boosted route, the digital versions of MSD’s 6 or 7 series boxes are part of a tunable package. If you don’t have the most optimum spark available for power adders, you’ll definitely be hurting parts as soon as you start to lean on the power.

About the author

James Lawrence

James started working on a Nostalgia Top Fuel drag racing team in 1992, and the rest has been history. A life-long automotive enthusiast, James is in fierce competition to see whether he can collect more cars or cats. Right now, the cars are winning. James co-founded the NMRA and NMCA Drag Racing Series in 1998 and continues to be an avid and passionate fan on everything 1320. He also thinks he can drive. Thinks, is the key word.
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