Do you need a switch?
The Wiring page for Rotational Idle starts with one choice: enable the Rotational Idle Switch or not. With it disabled, the function runs purely off its own conditions. With it enabled, the driver has to arm it with a physical switch. On anything that sees the street or the pit lane, we recommend the switch. It keeps the car quiet and gentle until you want the effect, and it gives you an instant way to turn it off. The connection settings below only appear once the switch is enabled.
SPI or AVI?
Under Switch Input, pick any spare SPI or AVI. Both work well for a simple on/off switch. They just decide "on" differently.
| SPI | AVI | |
|---|---|---|
| You set | Edge Select and Pullup | Switch On Voltage and Switch Off Voltage |
| How it decides | By which way the signal changes | By comparing the voltage against your two thresholds |
| Best for | Plain ground or 12V switches | When SPIs are used up, or unusual switch voltages |
SPI settings
- Edge Select: choose Falling if your switch connects the input to ground when you flip it on. Choose Rising if the switch feeds voltage to the input when on.
- Pullup: a ground-switching setup needs the pull-up enabled, otherwise the input has no voltage to sit at when the switch is open and the ECU can't tell on from off.
AVI settings
On an AVI you tell the ECU two voltages: one that counts as on and one that counts as off. Leave a healthy gap between them. That gap stops noise, voltage dips during cranking, or a slightly dirty ground from making the function flicker on and off.
Two ways it commonly looks:
- Ground-switched input: the line sits near 5V when the switch is open and drops to 0V when you close it. Set the on voltage low, around 0.5V to 1.0V, and the off voltage high, around 4.0V to 4.5V. The input only counts as on once it's pulled nearly to ground, and only counts as off once it's back near 5V.
- Voltage-fed input: say the input rests around 2.5V with the switch off and sees 12V when it's on. Then the on threshold sits above the resting level, for example 4.5V, and the off threshold below it, for example 3.0V.
Before you pick numbers, measure the real on and off voltages on the pin with the ECU's live data, then set your thresholds comfortably inside them.
Flip the switch a few times with the engine off and watch the switch status in NSP. It should change cleanly every time with no flicker. A ready-made dual switch panel kit is a tidy way to mount it.
Related: vehicle functions overview. If you're unsure which input to use on your harness, ask us.
