linewarbr wrote:
I know you have your own way of doing it JL, but. . . you pays your money, you takes your choice.
When you're putting temperatures between 900 and 1300 degrees F into your turbo, it's a good idea to let it idle for a bit to cool off. The issue is not metal temperatures, it's oil coking in the passages and return lines due to the temperature of the metal. Using 0W or 5W full synthetic oil makes it less of an issue, but still - I cool mine some, particularly after exiting the Interstate where I've been going 80 mph for the last hour or two.
Here is the turbo chart from the owner's manual:
If you are putting temps of almost 1300 to the turbo, you've got some real issues to resolve. The only way you would even come close to those temps in the turbo is if you had the accelerator to the floor and were pulling a heavy load up the side of Vail Pass in Colorado, on a scorcher of a day and keeping your RPMS too low for the pull! Getting to those temps is a function of exhaust flow, fueling, RPM and load. I never even approach those temps in the turbo on my Cummins ISX in my semi pulling 80,000 lb thru the mountains of W. VA on a 100F day. Really kind of hard to imagine you are doing it with a CRD.
That being said, turbo cooldown is not bad, but not the issue that most think it is. I have taken original turbos to over 1.4 million miles without worrying about turbo cooldown in all but a very few situations. I even have turbo blankets installed on most of my turbos, since there is a cooling effect as the exhaust goes thru the turbo and the slight cooling actually creates a restriction. By having a turbo blanket on, the temps actually run 100-200F cooler in the turbo because the exhaust is not being slowed down in the turbo by any cooling. Restriction is always the turbo killer. Total fueling under a hard pull with the RPMS too low will generate a considerable amount of heat. If driven right, even under hard towing and high speeds, no turbo will be at risk of reaching the temps you suggest. Speed and higher RPMS are not what causes a turbo to reach critical temps. It is restriction in the exhaust that keeps the exhaust from getting out of the cylinders, thru the manifold, by the turbo and on out that causes excessive temps. Too low of RPMS with high fueling under a hard pull will do this as well.
This is the primary reason I advocate that one of the first mods that ANYONE should do to any diesel engine is to open up that exhaust!!! Reducing the restriction there has the best bang for the buck in saving that engine and turbo. I am just about ready to go over 3 million miles commercial operating turbo diesels and have seen most problems with turbos are restriction in the exhaust which will raise EGT's higher than necessary. Opening up the exhaust can lower EGT's considerably and increase power to the rear wheels.
Just the running down your street a few blocks and coasting on into your driveway will cool a turbo down from even the most extreme temps it may have been at. Most good drivers will decelerate and coast onto the off ramp of a freeway and in that time, the turbo temp will drop considerably from the temp it was under during that hard running. Unless you have the accelerator to the floor, pulling 5000 lb up hill, on a 100F day, and then reach up and shut the engine off without even letting up on the throttle, you will never destroy a turbo from excessive heat and not allowing it to cool. Once you remove the fueling from the engine, the exhaust cools considerably and likewise the turbo cools soon. Plus the oil is still circulating thru the turbo and is also has some cooling effect as well. Of Course, a rotten driver can destroy a turbo as well.
Do your cool down routine as you wish. No problem. Just don't develop some sort of of superiority complex that those who do not do it like you are somehow inferior. That is based on feeling and not science.
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