Safe shutdown temp?

[Radshooter]

We just moved to Yuma AZ, and it is HOT here and getting HOTTER. It seems to take ffffooooorrrrreeevvvveeerrrr to get the turbo to cool down to 300 pre temp. It does seem to cool down to 350 pretty rapidly, but sometimes that last 50 can take awhile. I was wondering if a Pre-turbo temp of 350 is still cool enough for safe shutdown? If the outside temp is cool, it is not a problem to get to 300. But when it is still 90 outside, it takes a while.



Thanks..... Steve

 

[Jengle]

I noticed the same thing, now that things have warmed up to the 80s here the last two days. I found that shutting off the accessories, A/C mainly, speeds up the cool down.

 

[XJSuperman]

We've been running in the mid '80's here... getting down to 300 only take me about 10-20 seconds.

 

[Steve St.Laurent]

The A/C compressor running will make a HUGE difference in how long it takes to cool off the turbo. Not sure on the 3rd gen's but on the 2nd gens the only positions that the A/C compressor isn't running is the vent position and the floor position. Bi-level, defrost, and defrost/floor all run the compressor in addition to the A/C settings. I have a turbo temp monitor that automatically shuts my truck down at 300 degrees post turbo and if I leave the A/C compressor on it'll still be running after 15 minutes. I've never left it running to see just how long it would take if ever to cool down. If I forget and leave the A/C compressor on and it runs for a few minutes it shuts off within a few seconds of turning off the compressor.

 

[InThinAir]

My 01 takes an eternity to get to 300 Post turbo. I usually give it to 350 and shut it down. But it is not from the outside temperature for me. It is really never hotter than 70 degrees at my house.



So I have 90K on the 01 and it doesn't usually get a chance to get to 300 degrees. Don't know if it has hurt it?



But I will say I see people saying it only takes 20 seconds. To get to 350 post the average I have to wait is 5 minutes. And I have let it idle and run into a store in the winter and come out and it is still not 300 after 15 minutes. I don't run the A/C, I know that on the 2nd gens it is not necessarily your choice, so I stay away from the bi-level setting. But I thought that it was only the switch on the 3rd gens?



I will say that it has alot to do with what you do with the truck and where you live. I was in another post where someone said they hit 800 post turbo for the first time, empty. I hit it every day, and sometimes 900 empty. Using the 300 degree difference as a "rule of thumb" that is about 1200 degrees in the manifold! I have noticed that my paint has discolored on the hood, but is doing damage, I am not sure.





---Doug

 

[Steve St.Laurent]

Doug - you say you stay away from the bi-level settings but do you have it on either of the defrost settings? Those use the A/C compressor as well. There are only 2 settings on the 98-02 trucks that don't use the compressor (3 if you include off). At worst on my truck pulling a 10,000 lb load up a steep climb, a/c running until I come to a stop, using my exhaust brake to come to a stop, with an outside air temp of 90 degrees, have been running at 1200 degrees pre turbo for a few minutes it has taken ~10 minutes to get down to 300 degrees post turbo (as long as the A/C compressor is off). It usually takes two or three minutes to get down to 300 driving around unloaded hotrodding it (hitting peak EGT's of 1550). Normal driving it'll hit 300 within a minute or two.

 

[InThinAir]

I think that because my truck see higher temps due to the elevation and steep grades it retains the heat for longer. Idling trying to shutdown, I have never seen 300 post turbo in under 5 minutes. But in most cases, 5 minutes will get me around 350. That is, 99 times out of 100, where I turn it off. I am not using the a/c compressor, I stick to most the 2 settings once I read the facts in the owners manual and on this forum.



I have often thought that the BHAF just sitting in the compartment, leads to slower cool downs. But that is just a hypothesis...



---Doug

 

[rbattelle]

Originally posted by InThinAir

My 01 takes an eternity to get to 300 Post turbo. I usually give it to 350 and shut it down. But it is not from the outside temperature for me. It is really never hotter than 70 degrees at my house.



So I have 90K on the 01 and it doesn't usually get a chance to get to 300 degrees. Don't know if it has hurt it?



But I will say I see people saying it only takes 20 seconds. To get to 350 post the average I have to wait is 5 minutes. And I have let it idle and run into a store in the winter and come out and it is still not 300 after 15 minutes. I don't run the A/C, I know that on the 2nd gens it is not necessarily your choice, so I stay away from the bi-level setting. But I thought that it was only the switch on the 3rd gens?



I will say that it has alot to do with what you do with the truck and where you live. I was in another post where someone said they hit 800 post turbo for the first time, empty. I hit it every day, and sometimes 900 empty. Using the 300 degree difference as a "rule of thumb" that is about 1200 degrees in the manifold! I have noticed that my paint has discolored on the hood, but is doing damage, I am not sure.

These readings might be the result of your placement of the thermocouple. Mine is about 1/2 way around the outer radius of the turbine exit pipe. If yours is very very close to the turbine exit itself, I would expect it to read higher. Your high altitude may also play a part... lower density means less opportunity for heat transfer.