Most stock or mildly modified Harleys will benefit from the use of the VOES. The way the system works is; at part throttle or cruising speeds, when engine vacuum is high, the switch is closed and the ignition is at full advance by 1500 RPM. This results in increased fuel economy and improved part throttle drivability. When under heavy acceleration and engine vacuum is low, the switch opens, causing the Dyna 2000i to follow a slower advance curve. This helps to reduce detonation under heavy loads. More heavily modified motors can benefit from using the VOES switch wire in the optional modes outlined in the instructions manual.