What proportional gain does
When cruise control is active, the ECU is constantly comparing road speed with the speed you set. The difference is the speed error. Proportional gain scales how much throttle the ECU adds or removes in response to that error: the bigger the gain, the bigger the throttle change for the same error.
Too much or too little
- Higher gain gives quicker, firmer corrections, which helps on hills. Push it too far and control becomes unstable.
- Too high near the set speed is the most common complaint: the car gently surges back and forth around the target. It's subtle, but enough to make passengers carsick.
- Too low and the car is slow to respond, dropping speed up a grade before it catches up.
Our approach: start conservative, then raise the gain where the error is large so the car recovers quickly, and keep it lower close to the set speed where smoothness matters most. Then add integral gain to remove any steady offset, and only use derivative gain if you need to damp overshoot.
Check your units
The values in this table depend on the speed units chosen in NSP's Preferences menu. If you change from mph to km/h (or back), revisit this table.
