Why EKF2_ACC_NOISE is limited to 1. What happens if I exceed it?
I know in code it limited to 1 and I want to change it.
Nothing happens at exactly that threshold. However, you shouldn’t need to exceed this value for most setups. If you have a really good reason to increase it more (because your setup requires that), you should just be aware that you might need to re-tune other EKF parameters. The EKF will rely less on inertial navigation and will be more affected by aiding errors and the accel bias will take more time to converge.