What the switch does
The pit lane speed limiter holds the car to a set road speed using ignition and fuel corrections, and on drive-by-wire cars it can also cap throttle opening. The Wiring page sets up the input that arms it.
Which inputs you can use
- AVI (analog voltage input): works for a simple switch to ground or 5 V.
- SPI (synchronized pulsed input): also fine for a plain switch when you've run out of AVIs.
- CAN keypad: a button on a Haltech CAN keypad, with no extra wiring back to the ECU.
Momentary or latching?
The switch type changes how it behaves. With a momentary pushbutton, the limiter is active only while the button is held down. Let go and it switches off. That's common on steering wheel buttons, where the driver holds the button through the pit lane.
With a latching (toggle) switch, the limiter stays on until the switch is turned off. That's easier over a long pit lane or a transit stage, but the driver has to remember to turn it off.
Our advice
Label the switch clearly, and test it in the pits before the event. Check it arms and releases as expected and that the speed limit holds. Then set the ignition correction, fuel correction and DBW throttle max tables so the car holds speed smoothly instead of bucking against the cut.
