Why idle up matters
Switch on the A/C, turn the wheel at a standstill or put the headlights and fans on, and the engine suddenly has more work to do at idle. Without help, rpm sags, the idle controller notices and opens the valve, and you get a dip and a slight hunt. Idle Up gets ahead of that. Each load has a switch signal, and when it's active the ECU adds a set amount of base duty to the idle valve straight away and, where available, raises the target rpm as well.
Each offset only works once the matching function or switch is enabled elsewhere in NSP.
The offsets
| Load | Settings | Needs |
|---|---|---|
| Air conditioning | Air Con Idle Base Offset (duty added) and Air Con Idle RPM Offset (rpm added to target), applied while the A/C output is on | Air conditioner enabled |
| Power steering | Base Duty Cycle Offset and RPM Offset, applied while the switch is active | Power steering switch enabled |
| Electrical load | Base Duty Cycle Offset and RPM Offset, applied while the switch says a big load is on, like headlights | Electrical load switch enabled |
| Air pump | Idle Delay: waits for idle to settle before the air pump is allowed to load the engine | Air pump function in use |
| Generic idle up | Enable, Input and Base Offset, adding duty while the chosen input is active | Input set up as a generic sensor |
How we set the offsets
- Get the engine fully warm with the base idle tuned and stable.
- Turn on one load at a time and log rpm and idle duty.
- Watch how much extra duty the closed loop controller ends up adding to hold target. That's roughly the base offset you want, so the valve moves there immediately instead of waiting.
- Only add an rpm offset if the engine genuinely needs to idle faster with that load on, such as A/C on a small engine or charging at night.
- Test combinations, like A/C plus full lock steering plus headlights, to make sure they add up sensibly.
Too much offset causes an rpm flare every time the load switches on. Start conservative and confirm in logs.
Troubleshooting
| Symptom | Usually |
|---|---|
| Rpm dips then recovers when a load comes on | Base offset too small, or the switch isn't reaching the ECU |
| Rpm flares when a load comes on | Base offset too large |
| Offset has no effect | The related function or switch isn't enabled |
Idle Up works on top of idle control, so get the closed loop base duty and target rpm right first. If your engine uses an idle air valve, the Haltech idle air control motor is a common choice.
