Edit: Oops, replied to the wrong thread I moved it here ... "Water Steam Injection" https://listerengine.com/smf/index.php?topic=8949.new#newIt's unlikely that you will need water injection on a continuous basis so consider an algorithm to intermittently dose the engine.
You may already be aware, but the arduino "uno" and "mega"do not have WiFi capability.
If you wish to communicate with the system from the house, take a look at the Wemos D1R2.
Form factor and programming language is the same as Arduino but it has WiFi connectivity.
It even uses the Arduino programming software.
Costs around $10
The big difference with the Wemos is that it's pins are all 3.3vdc (like the raspberry Pi) unlike the Arduino which is 5vdc.
Buy local from Amazon. (As you know, ... EBay is not shipping from the Asia at the moment)
Make sure it's the Wemos D1
R2 . The older Wemos D1 has been phased out but there may still be some old inventory being sold.
cheers,
veggie