MSD Three Step Module Selector

As an example, we'll use a drag car with a Three Step Module Selec­tor plugged into the rpm socket of a 7AL-2 Ignition. The different rpm modules are activated when 12 volts are applied to a corresponding wire. By connecting one wire to the line-lock circuit, one module will be activated during the burnout. This helps keep tire temperatures consistent. When the line-lock button is released, the limit turns off. When you're on the starting line, you can activate the second limit through the clutch or trans switch. This provides a steady and consis­tent rpm for firm holeshots every time. When no modules are selected, the remaining high limit is active to protect the engine in the event of driveline failure.