How to Enable and Configure Betaflight Dynamic Idle to Improve “Prop wash”

Betaflight’s Dynamic Idle feature can improve prop wash performance for FPV drones. In this guide, we’ll walk you through enabling and configuring Dynamic Idle to achieve optimal results for your specific drone.

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Activating Betaflight Dynamic Idle

To enable Dynamic Idle, follow these steps:

1. Open the Motors tab in Betaflight Configurator and enable bi-directional D-shot. This allows Betaflight to read the RPM of each motor. If you have already enabled the RPM filter, then you don’t need to do this step.
2. Navigate to the PID Tuning tab and locate “Dynamic Idle” in the right-hand pane, under “Throttle and Motor Settings.” Set an appropriate Dynamic Idle RPM value based on your drone’s propeller size (e.g., 3000-3500 RPM for 5-inch props). Higher pitch props require lower values, while lighter props need higher values.

Note: When Dynamic Idle is set, the static Motor Idle percentage in the Motors tab is automatically disabled.

The recommended Idle RPM value depends on propeller size and pitch, smaller and lower pitch propellers generally require higher value. For 7″ you can generally set this to 14-28, for 5″ drones, 20-40, and for 3″ it’s higher at 33-66. When it’s windy you can also set this higher to counter.

Value too high, you lose hang time when you let the drone fall upside down (the motors push harder towards the ground). A high value will also tend to make the quad “hover” a little more even at zero throttle, making throttle management a little harder. When value is too low, you risk low throttle instability.

To set the value, depends on what ESC idle you had previously (default is 5.5%), test your motor in the motor tab, you can use a smoke stopper or bench power supply to limit current in case it goes out of control. Spin the motor at the ESC idle value, e.g. for 5.5%, move slider to around 1055, and see what the reported RPM value is (it will only show this if you enable bi-directional DShot). Then this RPM value would be the ideal value for your dynamic Idle value (divide it by 100).

The Importance of Dynamic Idle

Without Dynamic Idle, Betaflight sets the minimum RPM of motors by sending a fixed value (with a default idle speed of 5.5%). This can result in inconsistent RPM across all motors due to slight KV differences and battery voltage fluctuations (e.g., idle RPM at 4.2V will be faster than at 3.8V).

With Dynamic Idle, however, Betaflight can detect and read each motor’s RPM, allowing you to set the minimum RPM more precisely. But how does this improved accuracy benefit prop wash performance?

How Dynamic Idle Reduces Prop Wash

When prop wash occurs, the flight controller attempts to stabilize the quadcopter by rapidly speeding up or slowing down the motors. Without Dynamic Idle, the minimum RPM your motors can reach is 5.5% by default. In contrast, when Dynamic Idle is enabled, Betaflight can command the motors to drop to 0% RPM. This enhanced braking capability noticeably improves prop wash handling.

Wrapping Up

Enabling Dynamic Idle can lead to a notable improvement in prop wash performance. However, numerous other factors can also impact prop wash handling. For more tips on improving your drone’s performance, check out our comprehensive tuning guide: https://oscarliang.com/fpv-drone-tuning/