Originally Posted by 2trally
Whew, I can get the turbo idea outa my head. I want to be able to do water crossing, and water on a hot turbo = useless turbo with some warped turbines. I'm not 100% sure about that but for turbo cars and trucks they recommend letting the car idle for a minute before you shut the engine off to keep the turbines from cooling too quickly. Even in a setup were the turbo doesn't get very hot (relative to something like an rx7) dunking the thing in water would cool it more quickly than a rapid shutoff from high rpm and would definitely cause damage. And besides all that, the 690 makes good enough power already. If I got one I would be more concerned about making the electrical system reliable and getting some extra range.
Water on the hot turbo housing isn't likely to affect the blades, but I can imagine you'd run a good risk of cracking the thing. The reason for letting a turbo idle for a while before shutting down is to give it a chance to cool down, so the oil doesn't "coke" around the bearing. Shutting down a turbo after a hard run with no cool-down period is just like dumping your oil in a hot frying pan and walking away from it. If you do this often enough, the coked oil eventually clogs up the return line and packs around the bearing so that fresh oil can't run through the turbo bearing, resulting in failure. Most recent turbos have a water jacket around the center section to provide convection cooling after you shut the engine down to help prevent coking.