turbo cool down

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I was always taught when driving a diesel vehicle to always let the EGTS come down and let the truck idle for a few minutes after a hard run or when towing. I've always adhered to this . F250 in my sig, last night I got on the road(not towing anything), quickly got it up to 80 mph then turned in the median, got it up to 50 mph before pulling up to a roadside taco stand to order food. There were people ordering so out of courtesy I let it idle for about 30 seconds before shutting it off(engine is pretty loud). I know Im probably worrying for nothing but could that quick run to 80 mph coupled with the quick shutdown have damaged the bearings in the turbo? Truck is stock besides a straight piped exhaust and I'm running Supertech 15W40.
 
I don't know much about diesels so someone else may have better input.

However, I believe the reasoning for idling before shut-off is twofold.

First, you give the engine a chance to heat up and cool down evenly, as some parts of the engine generate more heat than others. Since different parts are expanding and contracting, it's probably good for wear.

Secondly, when parts of the turbocharger are hot they are hard on oil. Oil is flowing when the engine is running, so no big deal. But after a hard run the oil in the turbo doesn't move as much (other than slowly draining) so the hot spots have a chance to bake the oil much hotter than normal. The term for this is "coking".

It's a good practice to let the engine idle for a bit after a hard run or towing, but if you only did it one time I wouldn't worry. Don't make a habit of it, but doing it a few times is probably inconsequential.
 
This has been discussed before, you'll hear the engine was designed to be shut off w/o an idling period. Then you'll hear it is best to idle it for 30 seconds before turning it off. I agree with that. It is just like the drop the factory fill early on a new car debates that come up from time to time. There are two sides dug in deep on both topics.
 
The oil doesn't matter. Get a pyrometer to see the temps .When my wife bought her F250 7.3 back in 2002 the first thing I did was put a pyrometer in it. Summit auto parts sells them. The problem would be is when you shut down a hot turbo the oil can cook from the heat and the head can be well above any base oils flash points. I didn't drive the truck enough to remember the operation and temps in the 16 year we owned the vehicle.
 
Originally Posted by demarpaint
This has been discussed before, you'll hear the engine was designed to be shut off w/o an idling period. Then you'll hear it is best to idle it for 30 seconds before turning it off. I agree with that. It is just like the drop the factory fill early on a new car debates that come up from time to time. There are two sides dug in deep on both topics.

This website has replies of preconceived notions and occasionally facts. The hart part is discerning between the two.
 
Originally Posted by CT8
Originally Posted by demarpaint
This has been discussed before, you'll hear the engine was designed to be shut off w/o an idling period. Then you'll hear it is best to idle it for 30 seconds before turning it off. I agree with that. It is just like the drop the factory fill early on a new car debates that come up from time to time. There are two sides dug in deep on both topics.

This website has replies of preconceived notions and occasionally facts. The hart part is discerning between the two.

Exactly. Which is why it is important to do your own homework, and avoid believing blanket statements to be Gospel.
 
I've always waited a minute or so cool down from highway runs and don't do anything special for town driving.
 
Originally Posted by maxdustington
Water cooled turbos and auxiliary water pumps exist. It's not 1993 anymore, you don't need a turbo timer on your Eagle Talon TSi.


1. No matter how hard I drive the car, there's always a period of time where I'm not hard on the car before an "immediate" shutdown. What I mean, is that I've never driven at full-boost and then power-slid into a parking spot before immediately shutting the engine off; there's ALWAYS some engine braking while you slow down, some low-speed driving while you find a spot, etc.

2.
Originally Posted by maxdustington
Water cooled turbos and auxiliary water pumps exist. It's not 1993 anymore, you don't need a turbo timer on your Eagle Talon TSi.


All of my recent turbo Subies have had water-cooled turbos. The turbo (heat source) is lower than the radiator or secondary reservoir (heat sink), allowing for natural circulation of the coolant through the system, including the turbo, until the driving head (differential temperature between the coolant passing through the turbo) and that of the radiator is insufficient to overcome the differential height (gravity).
 
Originally Posted by mobilaltima
I was always taught when driving a diesel vehicle to always let the EGTS come down and let the truck idle for a few minutes after a hard run or when towing. I've always adhered to this . F250 in my sig, last night I got on the road(not towing anything), quickly got it up to 80 mph then turned in the median, got it up to 50 mph before pulling up to a roadside taco stand to order food. There were people ordering so out of courtesy I let it idle for about 30 seconds before shutting it off(engine is pretty loud). I know Im probably worrying for nothing but could that quick run to 80 mph coupled with the quick shutdown have damaged the bearings in the turbo? Truck is stock besides a straight piped exhaust and I'm running Supertech 15W40.

I owned BMW 525d E61 in Europe and made 425k km on it. I would do 120-130mph runs, get off HWY, drive normally 2-3 miles and turned it off. In those 2-3 miles, according to OBD I had hooked up, coolant and oil temps. go down to normal.
When I was doing 80-100mph with that car I never bothered cooling it off. And at 425k km did not use drop of oil, and could still top off at 145mph.
I would say, get more Taco's
smile.gif
 
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Hey everybody. I am writing for the first time on this great forum from far away Finland. I have followed with great interest what is written here. I could try to answer that question. Let's start with the diesel and gasoline engine efficiency. The efficiency of the diesel engine is better because the combustion process lasts longer on the piston than on the gasoline engine. Thus, thermal energy is converted into longer kinetic energy than in a gasoline engine. As a result, the exhaust fumes are cooler in the diesel engine than in the gasoline engine. It is also worth mentioning that I am following this forum, since petrochemistry in particular is of great interest and there are good answers here.
 
Originally Posted by billt460
Question for anyone who knows for certain..... Do turbochargers on diesel engines run cooler than turbos on gasoline engines?


Yes, they do. Hundreds of degrees (F) cooler at full power.
 
Originally Posted by mobilaltima
I was always taught when driving a diesel vehicle to always let the EGTS come down and let the truck idle for a few minutes after a hard run or when towing. I've always adhered to this . F250 in my sig, last night I got on the road(not towing anything), quickly got it up to 80 mph then turned in the median, got it up to 50 mph before pulling up to a roadside taco stand to order food. There were people ordering so out of courtesy I let it idle for about 30 seconds before shutting it off(engine is pretty loud). I know Im probably worrying for nothing but could that quick run to 80 mph coupled with the quick shutdown have damaged the bearings in the turbo? Truck is stock besides a straight piped exhaust and I'm running Supertech 15W40.


If you weren't towing or hauling at max GVW, it's not a problem. I have an EGT gauge on my Dodge, and if I'm driving unloaded at highway speeds, EGT is less than 400F if I back off at 75 mph and coast up the entrance ramp to a stop. If I'm toodling around town at 35 mph, it stays below 400 F if I let it idle 15 seconds before shutting it off. On the other hand, if I'm towing at 65 mph with the A/C on into a headwind on a 90F day, it can take a few minutes for EGT to drop below 375F. My normal thing is to wait for it to cool off to 350F before shutting down.
 
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You're worried about this while running Supertech oil?!?!?!!?!? LOL

You'll be fine for just every now and then. It it was that big of a deal on modern engines the computer would not let you turn if off until it was safe for the engine to do so.
 
I always let my car idle for a minute before shutting down, despite what all the yahoos say.
lol.gif
 
On the track we'd always run a cool down lap to cool everything down on the car (coolant, brakes, oil, etc.) When we went spirited driving, by the time we got into the neighborhood everything was within normal temperatures by the time we shut down the car. Like said above, unless you're flooring the car for minutes straight then slide into a parking spot and immediately shut down the vehicle, you'll be fine.
 
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