EVO Ignitions


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Stock H-D Evo Big Twin ignitions have two advance curves ---- a quick advance curve for part-throttle, light load running, and, the very slow advance curve for mid to full-throttle running. It is this second curve that determines the ignition timing when accelerating even moderately. While not the most common reason for 'soft' or 'flat' acceleration in the mid-rpm range, the stock Evo ignition doesn't help.

The Screamin' Eagle Evo ignitions have the same full throttle advance curve as the stock ignition. The only difference between the two is the rev limiter rpm which is 5200 for the stock unit and 8000 (much too high) for the Screamin' Eagle ignition.

Ignitions with quicker advance curves, such as the CompuFire (curves 6,7 or 8) or Dyna 2000 (#1 curve only) have aggressive advance curves and improve throttle response and part-throttle performance in the mid-rpm range, especially below 3000 rpm. These two examples are that only. There are other after market ignitions that also contain quicker advance curves.

Stock Twin Cam ignitions are more complex than the earlier Evo type. They use a manifold pressure/engine revolution rate system for choosing ignition timing for any combination of rpm and throttle setting.