Tired of dealing with pesky prop wash and inconsistent motor RPMs on your drone? Betaflight’s Dynamic Idle feature might be your solution. Here’s how to activate it and why it’s worth your attention.
How to Enable Dynamic Idle in Betaflight
Step 1: Enable Bi-Directional DShot
- Open the Motors Tab in Betaflight Configurator.
- Enable bi-directional DShot—this is crucial as it allows Betaflight to read the RPM of each motor. If you’ve already enabled the RPM filter, you can skip this step.
Step 2: Adjust Dynamic Idle RPM
- Navigate to the PID Tuning Tab.
- Find “Dynamic Idle” under “Throttle and Motor Settings” in the right-hand pane.
- Set the Dynamic Idle RPM Value based on your drone’s propeller size:
- 5-inch props: 3000-3500 RPM
- Higher pitch props: Use lower values
- Lighter props: Use higher values
Note: When you set Dynamic Idle, the static Motor Idle percentage in the Motors tab is automatically disabled.
Propeller Size and Recommended RPM Values
The ideal Dynamic Idle RPM value depends on your propeller size and pitch. Smaller and lower pitch props generally require higher values, while larger, high-pitch props need lower settings. Here’s a quick reference:
| Prop Size | High Pitch Props | Low Pitch Props |
|---|---|---|
| 31mm/1.2″ | 84 | 167 |
| 40mm/1.6″ | 62 | 124 |
| 2″ | 50 | 100 |
| 2.5″ | 40 | 80 |
| 3″ | 33 | 66 |
| 3.5″ | 28 | 57 |
| 4″ | 25 | 50 |
| 5″ | 20 | 40 |
| 6″ | 16 | 33 |
| 7″ | 14 | 28 |
| 8″ | 12 | 25 |
| 10″ | 10 | 20 |
Pro Tip: If you set the value too high, your drone might lose hang time when falling upside down, and throttle management could become tricky as the quad may “hover” more at zero throttle. Too low, and you risk low throttle instability.
Fine-Tuning Your Dynamic Idle
To fine-tune your Dynamic Idle value:
- Test your motor in the Motors tab. Consider using a smoke stopper or a bench power supply to limit current.
- Spin the motor at the ESC idle value (default is 5.5%) and note the reported RPM value (only visible if bi-directional DShot is enabled).
- Set the Dynamic Idle RPM by dividing the noted RPM by 100. This will give you the ideal Dynamic Idle value.
Why Dynamic Idle is Important
Without Dynamic Idle, Betaflight sets the minimum RPM of motors with a fixed value—defaulting to 5.5%. This can lead to inconsistent RPMs across motors due to KV differences and fluctuations in battery voltage (e.g., idle RPM is faster at 4.2V than at 3.8V).
Dynamic Idle, however, lets Betaflight detect each motor’s RPM and set a more precise minimum RPM. This improved accuracy is particularly beneficial for reducing prop wash, a common issue for drone pilots.
How Dynamic Idle Improves Prop Wash Performance
Prop wash occurs when the flight controller tries to stabilize the quadcopter by rapidly adjusting motor speeds. Without Dynamic Idle, the minimum RPM is capped at 5.5%, limiting the motors’ ability to brake. With Dynamic Idle enabled, Betaflight can reduce the motors’ RPM to 0%, providing better braking power and significantly enhancing prop wash handling.