Get maximum power with no detonation risk! The MSD 6-BTM CD ignitions are ideal for engines with a turbo or supercharger. Not only will they benefit from full power CD sparks, but there is also an adjustable boost/timing retard circuit to prevent detonation. The dash-mounted control knob lets you easily adjust the amount of timing retard from 0-3 degrees per pound of boost pressure. Dial away engine-damaging detonation by retarding the timing in relation to boost pressure, and run on the threshold of detonation for maximum power and efficiency. You also get overrev protection from the soft touch rev control. They work with 4, 6 (even fire only), and 8-cylinder engines using a distributor. They include rubber shock mounts and 3,000, 6,000, 7,000, and 8,000 rpm plug-in rev limit modules.