2-Step Rev Control For Digital 6Al Pn 6425 Or 64253 Only MSD IgnitionSince the new Digital 6AL Ignition uses rotary dials to adjust the rev limiter, our engineers were tasked with developing a 2 Step Rev Control that could be added to give racers the ability to switch to a low rpm limit to use on the starting line. There are two easy to read rotary dials that let you set the launch rpm in 100 rpm increments. There is an activation wire that connects to the transbrake, a clutch switch or to the line lock to activate the