WHICH TURBO??????

[dumbdunce]

goodsy,

while it's correct to say that the oil is supplied *primarily* for lubrication, for the relatively small size and load of the bearings in a turbo the oil supply is excessive in the extreme, and the oil coming off the turbo is much hotter than the oil coming in; if the oil is picking up heat from the turbo, it IS cooling it, therefore it is correct to say the turbo is oil cooled - even if it is a side effect it is very real. if you take away the benefit of the sump, oil cooler and associated cooling of the oil before it recirculated back to the turbo, the oil will get too hot and break down pretty quickly. the oil does cool the turbo.

also, correct that the coolant in a water cooled turbo may flash boil, as coolant often does in hotter parts of the head around the combustion chamber. agreed it's not desirable, but it does mean that the coolant is doing its job, absorbing heat from the turbo (head, etc) and carrying the heat to the radiator where it is disposed of into the air. if the coolant is boiling excessively in the turbo, the cooling system pressure is insufficient, the coolant does not have a high enough % glycol, there is insufficient coolant flow to the turbo, and/or the entire cooling system is under designed for the engine/turbo/driver combination.


cheers

Brian