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.

Choose dynamic idle value based on prop size, a general rule I personally follow:

• 1.6″ (40mm): 9000 RPM – 90
• 2″: 7500 RPM – 75
• 3″: 5000 RPM – 50
• 3.5″: 4500 RPM – 45
• 4″: 4000 RPM – 40
• 5″: 3000 RPM – 30
• 6″: 2500 RPM – 25
• 7″: 2100 RPM – 21

You should also adjust RPM slightly based on prop pitch, heavier props will have a lower RPM, for example on a 5″:

• 20-30 for prop pitch > 3.5
• 30-40 for props pitch < 3.5
• If not sure, just use 30 which works well most of the times

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/