It's hair splitting, either way.:thumbup: So long as the engine is not running, and you aren't actively spinning engine parts....... what difference does the coolant temp make? So long as it stays below it's boiling point, it's pretty much meaningless. Even then, the 'threat' is limited to coolant overflow, and the potential subsequent operation with too little engine coolant.
Not quite. Boiling creates? Yep, bubbles. When you make make bubble in the middle of a cooling jacket, they do to the highest point and sit there. That creates air in the cooling system, doesn't help cooling performance. The after run pumps circulate the coolant in reverse to alleviate this issue.
Localized boiling of coolant after engine shut down? Sounds like bad design, to me.
If someone buys a $150,000 car, and it sounds like it has indigestion when you are walking away from it......
I think the marketing department may request a 'fix' for that.
If there is no heat source, all you are doing is redistributing the heat that is already there. Heat soak starts from the cylinder, and works it's way into the head (and cylinder bore to a lessor degree), right? This is why the valve area in the heads will develop a cooked on layer of oil over time..... 'coking' as it's described. The heat from the cylinders travels 'up' and the head itself has very little heat transport from the water jacket.... it's all on the engine oil. No oil flow..... localized trapped heat, tar.
I'd agree, turbos add another level of complexity to cooling requirements. Piping 1500 degree exhaust to a turbine to run the compressor means heat soak will raise the temp on the turbine (and it's bearings) to extreme temps.
The water jacket will not help there, either. That sudden sharp spike of heat soak is what kills turbos..... and why it's a really bad idea to shut one down without letting it idle for a while, so the turbine has a chance to cool off some. If not.... it will cook the lube oil. As far as I am aware most turbos' turbines use and independant lube supply so that they can run oils that are much more resistant to this issue.
'Turbo rated' engine oil is some very good marketing........... It's not (as far as I am aware) actually supporting the turbo at all.
Might want to check all your knowledge of turbos. No OEM manufacturer uses a separate oil system for turbos. They get the crankcase oil, just like the rest of the motor. I haven't even heard of any aftermarket system that uses an entirely separate oil system for the turbo. Older turbo cars just had the turbo mid section lubricated and cooled by oil, most newer turbo cars (audi has since the late 80's) use oil to lubricate the bearings and coolant to cool the center section. This is another reason for the afterrun pump, to cool the mid section to prevent oil coking.
