ThunderMax for 2021 - 2024 Softail® Models
For EFI-equipped 2021–2024 Harley-Davidson® Softail models with Milwaukee-Eight® engines.
Replace your factory engine control module with ThunderMax EFI management and AutoTune technology. The 309-592 combines a replacement ECM with wide-band oxygen sensors to monitor exhaust oxygen and adjust fueling as you ride.
Designed for Softail installation: This kit uses the same ECM as ThunderMax 309-591 and includes a specially designed ECM caddy for secure mounting in Softail models.
How AutoTune works
Select and load a basemap suited to your motorcycle’s engine, exhaust, and other modifications. After installation and initial setup, AutoTune uses oxygen sensor feedback to make ongoing air/fuel ratio corrections.
The basemap provides your starting calibration. AutoTune refines fueling from that starting point as you ride.
Key features
- Complete replacement ECM: Replaces the factory module without wire cutting or splicing.
- Wide-band AutoTune: Uses 18 mm oxygen sensors to monitor exhaust oxygen and make fueling corrections.
- Knock correction: Uses the factory knock sensors to automatically adjust ignition timing when knock is detected.
- Softail mounting caddy: Included to fit and secure the ECM in the motorcycle.
- Tuning software: Free ThunderMax software provides access to tuning tools, diagnostics, and operating data.
- Diagnostics and data logging: Monitor and record information such as engine temperature, RPM history, and diagnostic codes.
What’s included
- ThunderMax ECM with AutoTune
- Wide-band oxygen sensors
- Softail-specific ECM mounting caddy
Check your exhaust before ordering
ThunderMax requires compatible 18 mm oxygen sensor ports in the exhaust head pipes. Verify that your exhaust has suitable ports before installation.
If your exhaust has smaller ports or no suitable sensor ports, modifications may be required. Weld-in sensor bungs are not included.
Installation and setup
Review the application-specific installation instructions before beginning. Installation includes replacing the factory ECM and oxygen sensors, securing the ECM in the supplied caddy, and completing the software setup.
Download ThunderMax software · View installation documents
This product is intended for "RACE READY" vehicles only and is not for sale or use on vehicles otherwise subject to emission control requirements. In the state of California, this product should not be used on any vehicle that is registered for use on public roads. Please view the ThunderMax 50 application guide for "STREET APPROVED" & ARB compliant produ