Pertronix 9LU-144 Ignitor II Adaptive Dwell Control for Lucas 4 Cylinder with Vacuum Advance Adaptive dwell maintains peak energy throughout the entire RPM range, reducing misfires while improving engine performance Develops on average 4 times more available energy between 3000 and 5000 RPM, and 2 times more available plug voltage Compensates for inherent electronic delay by adjusting the spark timing throughout the entire RPM range Synchronized peak current and spark timing reduces heat build-up Senses startup and develops more energy for quicker, easier starting