So I’ve basically I connected the turbo cooling with a smallish (6 or 8mm, can’t remember exactly) bore hose from the cylinder head to turbo then from turbo to bottom of rad.
The water jacket around the turbo core helps keeps the oil temps down and acts as a thermal barrier between the hot exhaust turbine and cold air turbine. Short term running without water cooling isn’t going to cause any issues but long term, wouldn’t fancy it myself….especially on an engine kicking out nearly 280bhp….also running without inevitably creates higher air intake temps.
Shouldn’t cause any issues to a correctly set up cooling system either - well at least it’s been fine on the two zetec turbo’s I’ve built to date.