Turbo Cool Down

[rjrkihap]

I was just wondering if anyone knows weather all turbocharged vehicles should follow cool down proceedures. I know there are some vehicles with sealed turbos with ceramic bearings and others like ours with oil fed turbo's. For example those guys with turbocharged sports cars, should they be concerned about cooling down before shut down or is this somthing unique to Diesels?



Just curious.



Ron

 

[EMDDIESEL]

Alot of cars like SAAB's have water cooled turbos (bearings actaully) so they dont require a similar cooldown since the bearings never get that hot. I dont know about all the sports cars, but alot are this way.

Waiting till 300 degrees Pre turbo before shutting down our ISB's is a luxury for our turbo's, not a requirement. I have been involved in the towing industry for 9 years and i have seen trucks that were abused driven hard and shut right down and there Turbos are still ok after 100,00 miles. It will help to prolong turbo bearing life, but if you are in a rush one day and dont have time to sit in your truck and wait till it hits 300degrees you are not going to hurt anything if you shut right down.

The landscaper who lives a few houses away has a 99' Cummins Ram work truck and he never waits to shut it down. He has close to 70k and never had any problems yet. He also uses cheap oil and Napa filters.

The bottom line is it is good to give the engine a chance to cool and to let the turbo cool enough where you dont have to worry about bearing coking problems with any Turbo vehicle. But if you cant always do it, dont lose sleep over it.

 

[Dr.Evil]

There's some other issues besides the plain bearing and the dissaster the oil does to them during repeated hot shutdowns. The trucking co. I drove for had 4 or 5 White RoadBoss II's with 903 Cummins V-8's in them. As some would say, "They were Rode hard and Put Away Wet". ALL of them cracked the turbo outlet flange off the turbine housing, due to heating & cooling stress after about 2+ yrs on the road.

DENNY... ... ... ... ... ... ... ... ...

 

[chuck3]

cool down.

You know I wonder if its really that important if you shut down at 300 or a little higher unless you have been towing hard? How many Rams out there with out gauges compared to the number with gauges? maybe one out of a thousand, ten thousand? What im getting at is they dont have a clue what there EGT is at shut down just as you and I untill we got gauges. It seems if this caused a big proplem we would hear about it. Just my 2cents.

 

[tntway]

ya know chuck3, until i got gauges, i wondered the same thing

 

[GSchlegel]

I used to deliver airplanes, and was taught to always idle the engine for several minutes prior to shut down. Usually I could plan the taxi so I could go to the tie down without adding any power. But if I increased power for even a second, I had to restart the idle time countdown. Our concern wasn't temp. , it was turbo RPM. As you know the turbo takes some time to spin down and the higher the RPM, the longer the turbo spins. And once the engine stops, no new oil flows to the bearings. I have tried to follow this with my CTD also. If you do the same, your EGTs will be ok.

Gene

 

[Texas Diesel]

GSchlegel:



Any idea what the EGT was? How long was the count down period?

 

[Champane Flight]

Found

I have found that on most shutdown situations that the Cummins ( unless just finnishing long pull with 20000lbs behind)turbo is cool enough to shutdown imediatly. I have my pyrometer installed post-turbo and bring it down to 300' and shutdown. This probably puts my actual temp at 500'+- a few. The rule of thumb 100' drop or increase for every inch from turbo. Most mechs will attest to a 600' rule for shutdown. If you pull into a town usually a few blocks of putting around to your house will bring the temps down to a point of non-worry.....

 

[Dr.Evil]

All engines, gas, diesel, or whatever go thru a hot-soak period after they are shut off, the engine actually gets hotter because the cooling system stops pulling heat out of the heads & block, etc. I've even seen this in air cooled Radio control Car engines. This occurs, but to a lesser extent in engines that are allowed to idle and cool down slowly. If You shut down a CTD, or PSD, or any POS, even a Vega or Pinto, thats been run REAL HARD and chop the engine off quickly it will probably boil over. Even the NASCAR Cup Cars do that in qualifying. So any time I run at speed for an extended period I let my engines idle for 3-15 minutes. Even My 20 HP Onan in My Cub Cadet.

DENNY... ... ... ... ... ... ... .

 

[GSchlegel]

Texas Diesel,

I don't recall the EGTs any more, but we gave the turbo at least 5 minutes at lowest possible idle. If I even cracked the throttle, I started all over again. EGTs were important, but more important was turbo RPM.

I've noticed with my digital SPA gauge that in the hot summer months with the A/C on, my EGTs wont drop below 300* no mater how long I wait, so I now shut off the A/C as I wait for the EGTs and RPMs to drop.

Gene

 

[JohnE]

Our (CTD) concern on turbo shutdown temps is due to oil coking. Dino oil will basically breakdown and leave carbon deposits in the turbo oil journals. 300° is a recognised limit for dino oil. Synthetics will go higher, but I haven't seen any that will put it in writing.



Coolant temperatures do rise when the engine stops beacause the water pump stops, too. The coolant is still extracting the 2000°+ heat from the combustion chamber and can no longer shed it in the radiator. Go to drag races or pulling competitions. Many use electric motor driven water pumps to smooth the cool downs on a very expensive engine after shutdown.



Diesel engines cool very well with idling due to the wide open throttle (WOT) pumping of lots of air. Take care, some gasoline engines run hotter and actually harder in extended idle. Idle is also the hardest the ignition system must work to spark that fuel to life.



John

 

[John]

Originally posted by GSchlegel

I've noticed with my digital SPA gauge that in the hot summer months with the A/C on, my EGTs wont drop below 300* no mater how long I wait, so I now shut off the A/C as I wait for the EGTs and RPMs to drop.

I noticed that with my SPA gauges as well. Additionally, I have both my ATS exhaust manifold and Banks 14cm2 turbine housing ceramic coated inside and out... cool downs take at least as long as when I had the Hitco/Geno's Garage exhaust blanket installed.



..... not that I'm *****ing mind you