The boost setting on an electronic speed controller (ESC) provides an extra burst of power by advancing the motor's timing electronically over an RPM range you can set.
By default, brushless motors have a certain number of degrees of timing, usually 30 degrees. Increasing the timing of your motor has a similar effect to using a larger pinion - it increases your top speed but decreases your torque and acceleration.
Because you don't need as much torque when you're already up to speed, ESCs allow you to boost the timing of the motor once it hits a set RPM range. ESCs will normally have three boost settings - the boost amount, a boost start rpm, and a boost end rpm.
Boost start RPM
As you accelerate, the boost will start taking effect once you hit the boost start rpm.
Boost end RPM
As you continue accelerating, the number of degrees of boost will increase until you hit the boost end RPM, and then the boost will stay constant.
The boost amount or boost level (or just "boost") will increase linearly as your RPMs increase from the boost start to the boost end.
Some ESCs, instead of letting you set the boost end RPM, have a setting for ramp which determines how quickly the boost increases. The boost will stop ramping up as soon as it hits the max boost value.
Let's say your motor's timing is 30 degrees, your boost is 10 degrees, your boost start is 5,000 rpm and boost end is 15,000 rpm.
In this case:
- When you start accelerating and you're still below 5,000 rpm, the boost will be 0, so the timing will 30 degrees
- When you hit 5,000 RPM, the boost will kick in, and your timing will gradually increase
- When you hit 10,000 RPM, half of the boost should have kicked in, so your timing would be 35 degrees
- When you hit 15,000 RPM, the full boost is in effect, and your timing is 40 degrees
- Over 15,000 RPM, your boost will no longer increase, so the motor timing will still be 40 degrees
When using turbo and boost, pay close attention to how hot the ESC and motor are getting. You'll want to experiment with them on practice runs, so they don't overheat on you during a race.
See our article on electronic speed controller for more info on ESC settings.