Harley-Davidson 121 Tuning
1 supported Harley-Davidson 121 application, 2023+.
Harley-Davidson
1 supported 121 tunes
Harley-Davidson 121
121
117 HP stock / 136 lb-ft
2023+
- Controller
- Engine (ECU): Delphi MT21M
- Flash method
- OBD port, Bench
AutoTunerBook a tune
All Supported Harley-Davidson 121 Tunes
| Engine | Years | Version | Stock power | Controller | Platform |
|---|---|---|---|---|---|
| 121 | 2023+ | 117 hp | ECU Delphi MT21M | AutoTuner |
Other Harley-Davidson Models
About Harley-Davidson 121 tuning
Rapid Racing supports 1 Harley-Davidson 121 application from 2023+ through AutoTuner, with stock outputs up to 117 hp. Every calibration is built for your exact engine, fuel, and modifications, then verified on our Dynojet 424xLC2 in Jenison, MI, serving Grand Rapids and West Michigan.
Supported engines: 121.
Supported controllers: Delphi MT21M.
Don't See Your Vehicle?
These lists cover off-the-shelf tuning platforms. We also do standalone ECU installs and custom calibrations, so reach out and we'll tell you what's possible for your build. Compatibility data last updated 2026-09-24.