ThunderMax is a performance-driven, award-winning ECM built exclusively for EFI-equipped Harley-Davidson® motorcycles. Designed as a stand-alone replacement for the factory ECM, the 309-605 arrives fully assembled with wide-band oxygen sensors, plug-in harness, AutoTune module, USB communication cable, and everything you need for a straightforward install—no wire-cutting, splicing, or dyno required.
At its core, ThunderMax uses proprietary AutoTune technology and a closed-loop control system to continuously read, adjust, and perfect your air/fuel ratio in real time. With fueling points mapped every 1.5° of throttle and every 256 RPM, the system delivers unmatched precision for smooth, consistent performance in all riding conditions. A built-in barometric sensor accounts for altitude and ambient air changes automatically—just load the map that matches your build and ride.
The ThunderMax 309-605 also features knock correction for timing adjustment, adding another layer of performance by adapting ignition timing on the fly. Unlike other aftermarket tuners, ThunderMax fully supports factory features, so your ride modes, Wi-Fi, and navigation all continue to work seamlessly. This ECM is compatible with both VVT and non-VVT bikes.
Riders get complete flexibility: run a basemap and let AutoTune handle the rest, or dive into the ThunderMax software—free to download from the Thundermax website—to fine-tune AFR maps, ignition timing, startup fuel, idle speed, rev limits, and speedometer calibration. The system also offers data collection and diagnostic capabilities, letting you log, monitor, and analyze critical engine metrics for deeper insight into performance.
The result? Sharper throttle response, stronger rideability, and that deep, tuned exhaust note that makes the bike yours. Compatible with high-performance cams, turbo, nitrous, and supercharger applications.
How easy is it to fit? Well click on this link to see us install one on a 2024 CVO ST
NOTE 1: Pricing includes shipping if sold with mufflers or headers ONLY. Shipping as a single item is additional.
NOTE 2: ThunderMax ECMs utilize 18mm O₂ sensors. Factory exhaust systems are equipped with 12mm ports; TAB Performance headers come with both 12mm and 18mm sensors. If using a factory exhaust, you may weld in 18mm bungs. Bungs are not included.
NOTE 3: Fitment for 2023-Up Roadking®,2023-2024 Ultra®, and 2023-Up Trikes® require part number 309-591