I've been running Snows stage 2 for nearly 9 years with zero issues. It won't rust a motor if you know what the hell you're doing. Running a 225ml/min and a 625ml/min nozzles. I run windshield washer fluid mixed with water soluable cutting oil to keep pump and solenoid lubricated.
The water soluble oil is WHY you don't see a problem..... and you don't even know it!
Without any oil in the water the cylinder heads WILL look like they have been left outside in the rain on teardown.
It's real simple, just run a water soluble oil, then run the smallest nozzle(s) you can that keep the EGT where you want it.
Other than that, just make sure you have a solenoid right at the injection point so that you don't risk a hydro if you park on a steep hill, plus no dribbling.
Yes, I've torn down engines and seen insane rust. Only one of them had started picking up blowby. Twice it was my own engine, driven every single day.
Started running cutting oil from Napa and never had another issue.
In fact, adding the cutting oil to an engine already with increased blowby calmed it back down and the blowby went back to normal after a few weeks.
Water alone is a serious problem. Anybody that says otherwise hasn't ever had the heads back off, has their CCV in a position that they cannot see, injects almost nothing anyway or just doesn't have many miles on the setup.
Fwiw, I ran 2 of the largest nozzles they offered with two pumps to have any effect on EGT.
I later ran a pressure washer pump on a 12v starter motor mounted to the frame with stainless steel pressure washer nozzles in order to overcome 90 to 100 lbs of boost and still have enough pressure to inject enough water to matter. Ran about 350psi water pressure on that setup with two nozzles at the engine and one nozzle after the first stage turbo that kicked on when the first stage was over 20lbs.
Worked perfectly, and with the cutting oil, no rust was in my heads at all, and no blowby issues.
Injection quantity means nothing. OIL means everything. Sure you can start too early, or God forbid run the thing based on EGT :doh: and hydro your engine, but just don't do that. Was talking to a guy back in the day about controlling the water and he warned me against EGT (although I never even considered that an option) saying that he was rolling on the power and the EGT came up enough to kick too many nozzles at once (without much boost) and the engine hiccuped for a second and snapped the input shaft on the trans!
Always run off of boost pressure IMO. Maybe a second or third stage nozzle on EGT.... maybe... at least on a street engine where blowing white smoke and drowning things out like a mod puller with a gallon of water in the crank that will get changed out after each run anyway isn't exactly acceptable.