hmmmm this one has me scratching my head a little.

Been around cars, trucks, machinery and aircraft my whole life. I'm a firm believer in following the owners manual.

The manual states to prolong engine life idle 3-5 minutes then goes on to say especially after running it hard (in so many words).

I definitely sign up for 3-5 after running hard but 3-5 during a day of running errands stopping eight or so is not realistic.

Again I'm a firm believer in the owners manual and it suggested 3-5 for prolonging engine life. I don't plan on keeping it more than 250K...

 

I shut down the engine when I see the EGTs drop under 300°F and on a steady decline.

 

Here's a tip for those with remote start might find useful

After running with a load where you think the idle time is needed...

Shut her down and immediately restart with your remote start. You can preset the run time for 5 minutes. The remote ensures your truck is locked and cooling down for 5 minutes while you're inside eating supper.

 

awesome man! Good idea
Worry warts can bump the run time to ten minutes if it makes em feel better.

 

Should be able to install a cool down timer as well I expect. Some run for a fixed time after the key is turned off, other use EGT as well to determine run time.

I just idle about 30secs on a normal drive and a couple of minutes if shutting down after working it.

 

I let my EGT's get down under 400, and oil temp under 200, since it lubes the turbo. Doesn't matter if it's 5 seconds or 5 minutes. Egt's are normally quick to come down. Oil temps takes longer, and is more important to me. All dependant on outside temps and how hard your running your truck.

 

Works good too if you have to shut down a regen in process or right after a regen has completed; will allow that fuel already sent to DOC to get the most bank for the buck heating the DPF and lowering soot level.

Bob

 

If I'm correct, EGT1 would most accurately display the temps coming off the turbo so it is the one to watch. Since the turbo has cool intake air on one side and hot exhaust gas on the other then one could assume the bearing temperatures are somewhere in between. Of course once the engine is shut down and cool air and oil stop flowing then the exhaust side heat would migrate into the bearings. I never see my EGT1 temps above 800 which would be during a regen, but that would be the most critical time to let it cool down.

Since Rotella T6 and other turbo diesel engine oils are formulated to take the heat then it only makes sense to use them.

 

The one factor that you are not taking into consideration is the location of EGT1. The exhaust gas temperature is always going to be at least 100* higher at the turbo than it is at EGT1. This is why you always want to install a pyrometer probe pre-turbo to show the EGT at its highest. The liquid cooled turbo and the mass of steel between the manifold and the location of EGT1 on these trucks is going to absorb/dissipate some heat prior to the EGT1 probe.

The other factor in this is that after the engine has idled for say a minute, the actual combustion temperature is only going to be just over 300*. The higher temps that we are still seeing at EGT1 is the excess heat that the cooler combustion gasses are carrying away from the manifolds, turbo and down-pipe. This is why <400* at EGT1 indicates a safe point to shut the engine down. Since the exhaust gasses are well below that temp at idle, the temp reading now closely indicates the temperature of the turbo because it has become the greater source of heat in the system.

Why Ford doesn't build a turbo timer into these trucks is beyond me. For the average use that most of these trucks see, cool down time isn't going to be a major issue, but during an active regen, EGT1 temps can easily be 600-700* without much load on the engine. Since without a Scangauge or Edge Insight, we have no indication (other than the 3 second notice at the start of regen) that you are in active regen or when it has completed. This seems to be the most critical time for extended idle before shutting it down. They should build an automatic cool down timer to shut the engine down on its own terms at least during regen. There is no way to prove it, but I would bet that many of the non-tuning related turbo failures that have happened on the 6.7 are related to people just shutting it down like a gas engine especially during regen.

 

Just my experience, so take it as you please

Have had multiple turbo'ed vehicles for a long, LONG time and never replaced a turbo and never stay put for cool down... I will say one 1980 gas turbo had an automatic cool down turbo, but none of the mfg's since have had that...

in my humble opinion, if they thought it was needed they would continue to put it on

If I'm running hard on the interstate and have to stop for fuel, etc...
the service roads, stop signs, slow pull into next to the pumps, the arguments about who gets to potty first always takes more than enogh time to do any 'wanted' cool down...

And given the new oils and new materials in current day turbo's I'm not convinced a cool down is necessary...