Originally Posted by Stacked6600
What is your method Killerbee or do you have one?
Personally on a normally daily drive when you get home if you wait for the EGT to drop to 300deg that will take anywhere from 30 seconds or more depending on your truck setup. Factory trucks may take longer. But it is not a reference of the degrees but the time it takes to drop too 300 Deg. After I have been pulling a load for a while it can take up to 5 min to get it to 300deg . Usually it will set on 400-500 for about 3+ min. So it is not in reference to the actual EGT TEMP but to give a delay before shutting it off. It is an easy reference.
Now personally I will let my truck set and idle for long periods of time after a good haul it is not uncommon for me to leave it running for 30 min before I shut down. Do you have to ….. NO I know guys that never run thought cool down and their trucks are running just fine. Personally i think it is a good idea ...
FWIW, I don't use a method, but common sense, like you have shared in your post. Though I have an idea that 30 minutes is a 29 minute waste of the ozone layer. But your point is well stated, and the most important thing is having some situational awareness that the charger is hot, like you say, after sustained high load boost.
What is really an improvement these days, over the oil cooled designs of yesteryear, is that the water jacket will liberate an enormous amount of heat vaporizing the coolant locally. This act keeps the turbo oil well below the 450 degree coking temps, as the evaporation occurs under 300 F.
But if I were going to suggest a better method, for the older turbos that are not jacketed, it would be oil pan temps. Even that has some debate, but at least you are measuring the properties of the medium that is the applicable concern, oil, and oil coking.
I don't remember ever hearing about a coking issue with these turbos, so this whole thread, and the countless others like it, might be mute discussions.
In my own venture, I did find that it is very difficult to get EGT to reduce, and in a big part of that was the rise in airbox IAT as it sits idling, compounded with no flow over the CAC. It is physically impossible to get EGT below 350 degrees here, as others will report from time to time. IAT will rise as high as 190 sitting in the drive, and post CAC temps have gone to 240. That is because of the AC condenser heat load, and the ever rising IAT. So I guess the "300 or whatever" rule is arbitrary.