Why spray water?
Water injection, sometimes called anti-detonant injection (ADI), sprays a fine mist of water into the intake charge, or straight into each cylinder. As it evaporates it soaks up heat, and cooler intake and combustion temperatures make knock less likely. Some cars had it from the factory, the Saab 99 Turbo S being a well known example.
In racing, that extra knock margin can be spent on more boost, more ignition advance or a higher compression ratio. Aftermarket kits are widely available, and the Elite's Water Injection function can control when yours turns on. For background on why knock margin matters so much, see what knock is and why you should control it.
Wiring tab
Pick an output for the water injection system, normally a DPO or a stepper output. Like other Elite switching outputs, it pulls to ground. On most kits it drives a relay that powers the pump, rather than running the pump directly. Our relay guide covers the basics.
Active State defaults to Low, which grounds the output when water injection is on. High inverts it: grounded when off, open when on. Only change it if your kit's controller expects an inverted signal.
Water Injection tab: when it sprays
The output only turns on when all three conditions are true at the same time:
| Condition | What it means | Our advice |
|---|---|---|
| RPM | Engine speed must be above this value | Once on, it stays on until RPM falls 1,000 rpm below the setting, so it won't chatter on and off around the threshold |
| Load | Engine load must be above this value | Set it where you start making meaningful boost. Spraying at cruise just wastes water |
| Air Temperature | Intake air temperature must be above this value | Keeps it off on cold days when the engine doesn't need the help |
Because every condition must be met, the function is simple and predictable: high RPM, high load and hot air. That is exactly when a turbo engine is closest to knock.
If you add boost or timing because of water injection, the engine now depends on it. Keep an eye on tank level and make sure a failure can't leave you at full boost with no spray. Log knock activity with your knock detection set up before you lean on the extra margin, and be conservative until you've proven the system.
FAQ
Can I use this for water/methanol kits?
The function simply turns an output on when conditions are met, so it can switch any kit that runs from an on/off signal. Tuning for a methanol blend is a separate job, and one we're happy to talk through.
Why won't my water injection turn on?
Usually one of the three conditions isn't met. Log RPM, load and air temperature together and check which one is holding it off, then confirm the output and relay wiring.
