MSD Box Basics: Ignition Controller Buyer's Guide
The majority of stock ignition systems are inductive ignitions. The drawback here is the output voltage efficiency, specifically under heavy load and high rpm conditions. The coil has to store battery voltage and transform it to high voltage between each fire to jump the plug gap. This works great on factory vehicles or for general road use, but let's face it, when it comes to needing performance, it falls short. At higher rpm, there is less time to charge the coil to full capacity, and just when you need it most, the voltage fails to reach its maximum output, resulting with a loss of power or misfires at the top end.
The fix is easy with some help from MSD Electronic Ignition Systems! Let’s take a closer look at MSD’s 6 series Ignition Boxes that Speedway offers. It had been about 25 years since we had last seen an update from MSD, and back in 2010, MSD hit us with the newly designed fully digital 6 series line-up. One major improvement is higher output while consuming less energy. The digital boxes will deliver around 530 volts to the coil, in contrast to the out-dated analog boxes, which produced around 470 volts. Let’s compare that to a stock ignition system at 12 to 14 volts, meaning a huge increase in performance and drivability especially under heavy load and at high rpm. The 6 series ignition boxes are compatible with 4, 6, or 8-cylinder engines and are designed to work with points or electronic distributors. Depending on the unit you choose, they are capable of controlling timing, spark curves, single and dual stage rev limits, and variable ignition retarding for boosted applications.
The 6A box is a popular option for the average street and strip application or hobby stock and modified classes. However, if you’re above 12.5:1 compression or 8 pounds of boost you may want to consider the 7 series line-up. The basic 6A offers multiple spark up to 3000 RPM, capacitive discharge, and it’s designed to be used with externally modulated timing controls. The 6A produces full power multiple sparks at each plug, but the number of multiple sparks that occur decreases as rpm increases, the spark will always last for 20 degrees of the crank rotation. Shop 6A Ignition Box.
Anyone looking for rev control, the 6AL unit is the option for you. The on-board soft touch rev control is one of the main differences between the 6A and 6AL. This means no external rpm modules to plug in anymore, simply adjust the rotary dials located on top and you are ready to go. Like the 6A box, the 6AL has a primary voltage of 520 – 540 volts and secondary of 45,000. The 6A and 6AL series have been dyno tested to deliver efficient spark up to 15,000 rpm. Shop 6AL Ignition Box.
As an upgrade to the 6AL, the 6AL-2 offers a two step soft touch rev control using four rotary dials that are adjustable in 100 rpm increments. This means you can have both a staging rev control for the drag strip, plus a high rpm limit. The 6AL-2 is wrapped in the all new cast aluminum housing with primary voltage rated at 535, secondary at 45,000 volts. It can be used with Hall-effect, points and mag pickup triggers. Shop 6AL-2 Ignition Box.
The 6BTM is designed specifically for supercharged or turbocharged applications. This box offers the ability to control the timing and rev control, but also retard the timing in proportion to the boost pressure by using dash mounted control unit. It’s adjustable from 0-3 degrees of timing per pound of boost, you simply hook up your vacuum line and the box will do the rest. The BTM is supplied with plug in rpm modules for 3,000, 6,000, 7,000, and 8,000 RPM rev limits. Shop 6BTM Ignition Box.
-The Distributor MSD’s 6 series control boxes are designed to work with any points or electronic style distributors. We recommend installing a new distributor cap and rotor whenever you're installing a CDI ignition. Always inspect the terminals and rotor tip. On smaller caps, it is possible for the air inside the cap to become electrically charged causing crossfire. This can be prevented by drilling small vent holes between the terminals in the cap at the same height as the rotor.
-The Coil The 6A and 6AL ignition can be used with most stock coils and aftermarket coils. MSD’s line-up of Blaster Coils are great options for street and mild racing applications. For extended or high rpm, we recommend Blaster HVC, MSD part number 8252 or HVC II, PN 8253.
-Spark Plugs and Wires Just as it is with anything, your ignition system is only as good as its weakest link. That being said, it’s important to have a quality set of helically wound plug wires such as MSD’s 8.5mm Super Conductor Wire. It features a conductor that is helically wound around a special center core that is designed to suppress Electro Magnetic Interference (EMI). It’s important to always use a heli-coil wire anytime you’re installing one of MSD’s Ignition Control Boxes. Solid core wires will not suppress the higher spark output generated by the CDI. Be sure your wires are properly spaced and routed correctly to avoid cross fire. For plug wire routing, you can see MSD’s engine firing order chart.
It’s important to have a quality spark plug for the best performance, since there are so many combinations and manufacturers, MSD does not recommend any specific gap. However, we do recommend following the engine builder or manufacturer’s specification for spark plugs. You can experiment with the plug gap to get the best performance by opening the gap in .005” increments. Here are some examples as a good place to start. Keep in mind that every application performs differently and should always be tested and tuned.
Compression Spark Plug Gap
- Up to 10.5:1 - 0.050" to 0.060"
- 10.5:1 to 13:1 - 0.040" to 0.050"
- Above 13:1 - 0.035" to 0.045"