I know this is nitpicking, but let's say we have a Lycmning TSIO-540 or similar, and want to add an air cooling system based on water.
1. If it's a turbocharged engine, what about using bleed air (or excess wastegate pressure) to pressurise the water tank, and use a valve linked to MP indications and/or throttle position to control flow? No pump needed!
2. Alternatively, what about using a venturi arrangement in the engine air intake - the faster the airflow, the more water gets sucked into the venturi.
3. With regard to water freezing - how about antifreeze?
4. Corrosion - use aluminium?
Apologies, I'm sure these ideas have been thought of before, you'd probably need a lot of water to make this really work!
Confab