ThunderMax for 2021 - 2024 Softail® Models

Part Number: 309-592

Note: The ThunderMax 309-592 kit uses the same ECM as part number 309-591 but includes a specially designed ECM caddy for Softail fitment, making installation clean and secure for Softail models.

ThunderMax is an award-winning, performance ECM designed specifically for EFI-equipped Harley-Davidson® motorcycles. This advanced, stand-alone tuning system uses proprietary AutoTune technology with wide-band oxygen sensors to deliver unmatched performance, rideability, and adaptability.

The ThunderMax ECM comes fully assembled, ready to install, with no wire-cutting or splicing required. Simply replace the factory ECM and oxygen sensors, load a base map, and ride. Installation is quick, and the system immediately begins tuning itself to your bike.

With built-in knock control for timing adjustment, ThunderMax offers precise spark management in real time. It retains full factory functionality and works seamlessly with factory systems. Wide-band O₂ sensors continuously read the air/fuel ratio, automatically making live adjustments across every throttle position and RPM range. No dyno is required, and once you key off, all changes are instantly written to the ECM.

The ThunderMax software is free to download from our website and provides full access to tuning tools, diagnostics, and data collection. Riders can monitor, record, and examine critical information such as engine temperature, RPM history, diagnostic codes, and more.

Notice: ThunderMax ECMs utilize 18mm O₂ sensors. Factory exhaust systems are equipped with 12mm ports; however, nearly all aftermarket exhaust systems are manufactured with 18mm ports. If using a factory exhaust, you may weld in 18mm bungs. Bungs are not included.