S&S Cycle S&S Intelligent Spark Technology Ignition System for Harley Davidson All Big Tw Manufacturer Part No : 55-1221 The S&amp;S Intelligent Spark Technology ECU module automatically adjusts ignition timing When detonation is detected by the exclusive knock sensor, the ECU retards the ignition timing to prevent engine damage When detonation is not present, ignition timing is advanced for maximum power and economy The system &rsquo;remembers&rsquo; the conditions that cause the engine to knock and automatically adjusts ignition timing to prevent it when those conditions reoccurIf a different camshaft is installed or if cylinder head modificationsare made, the S&amp;S Intelligent Spark Technology ignition system will automatically optimize the ignition timing for the new configuration