water cooled turbo?

[Haynesie]

My turbo's center section has the usual oil feed and oil return sections, however on the other axis of the center section on both side there are two large threaded areas, about 3/4 to 1 inch large, any idea as to what these are for, im assuming for water cooling but i have no idea really

 

[turbo2nr]

YUP, water. Only used after shut-down. Heat soak will continue to raise temp of CHRA. Water (coolant) needs a resivour (spelling?) above the turbo to keep steam out of turbo and coolant inside. Factory cars with water center turbos have an extra tank of coolant above turbo for this reason. Just plumbing in coolant without a volume of coolant higher than turbo will do nothing after shut-down. Steam will be produced during heat soak (no more cooling turbo), and oil may still coke up. Look at a Subaru engine bay, and you will see the extra coolant tank next to the turbo, but higher. John Craig explained this to me. Thats why it is pointless to have a water cooled turbo in a GN, with the current cooling system.