Turbo heat

[What do I know]

Hey guys, new to the forum and have a quick question. My Kubota has a turbo. Do I need to let the tractor sit there and idle for a while before I shut it off to cool down the turbo? And do I always have to do this ( if I have to ) even if I am just putting around the yard? Thanx

 

[motownbrowne]

Yes, any turbocharged motor would prefer you to allow a brief cool down period before being shut down. Especially after working under load. If you're just putting around the yard, i don't think that would even begin to put a 100 HP motor under load, so in that instance, I think you could skip it, or maybe idle for 10 seconds.

PS. I sure wish I had an M100GX to putt around the yard in!!

 

[DK35vince]

Just after a heavy load a little cool down time would be good. By the time you drive it back to the barn and park , that would be enough.
Puttering around the yard= no cool down time needed.

 

[dieselcrawler]

On my daily driver, turbo diesel truck, I have an EGT gauge... climbing the hill to my house, mile and a half of steep grades and hair pin turns, I often see 1000° to 1100° readings. Top of the hill to my house is half a mile, by the time I cruise around that in the 800° range, it only takes a minute or so for the EGT to fall below 400° once I pull in the driveway and park. I leave it run for the time it takes me to gather my lunchbox and stuff, by this time it's around 350°, in the safe zone. 400°+ and the oil in the turbo bearings will 'coke' from the heat, basically burning out the liquid and leaving the solids as gritty gunk that chews up the turbo shaft bearings in time.

So, like others have said... puttering around the yard isn't gonna hurt to just shut it down. If you just got to the end of a 100ac field pulling the biggest plow you can, it would be a good idea to let it low idle 5 to 10 minutes. Use common sense.

Hope my long winded agreement with the others above helps...* grin *

 

[What do I know]

Awesome, thanx for the info. I guess that goes for winter operation as well. Will be blowing some serious snow this winter.

 

[MHarryE]

I see above you have a M100GX. Same panel as my M135GX. I usually have one of my readout a set to DPF temp and before shutting down, let it drop below 400. It doesn't take long, especially since it's usually running at low engine speed down my driveway before I shut down. But turbo or not, it's a good practice to idle before shutting down after working hard to let the cooling system bring the engine parts to a more even temperature. I mean even race cars get a cool down lap.

 

[Jerry/MT]

Hey guys, new to the forum and have a quick question. My Kubota has a turbo. Do I need to let the tractor sit there and idle for a while before I shut it off to cool down the turbo? And do I always have to do this ( if I have to ) even if I am just putting around the yard? Thanx

Check your owners manual for this advice. Our New Holland OM a one minute cool down @1200 rpm after full power operations. I believe it's to minimize rubs in the turbine section from a hot wheel and a quickly cooled outer case.

 

[DieselBound]

Check your owners manual for this advice. Our New Holland OM a one minute cool down @1200 rpm after full power operations. I believe it's to minimize rubs in the turbine section from a hot wheel and a quickly cooled outer case.

It's bearings and not the turbine wheel itself. The wheel should never come in contact with the housing: this only happens when a turbo is on its way out (you'll hear it, hopefully before it totally destructs). You're wanting oil circulation to pull away excessive heat from the shaft and bearing; by idling for a bit your stripping heat away before coming to a stop. It's like car brakes, after hard stops you're best off not holding down on the pedal because that causes concentrated heat build-up (lays down brake material non-uniformly, a kind of coking).

 

[Jerry/MT]

It's bearings and not the turbine wheel itself. The wheel should never come in contact with the housing: this only happens when a turbo is on its way out (you'll hear it, hopefully before it totally destructs). You're wanting oil circulation to pull away excessive heat from the shaft and bearing; by idling for a bit your stripping heat away before coming to a stop. It's like car brakes, after hard stops you're best off not holding down on the pedal because that causes concentrated heat build-up (lays down brake material non-uniformly, a kind of coking).

My NH manual specifically states it's to prevent rubs. As I stated previously, after running at full power for long periods, the turbine wheel is very hot and is at its max diameter. The outer case cools quicker with the ambient air and it literally shrinks to a diameter that will cause a rub if you chop the throttle and shutdown. The bearings are running in oil which is cooled by a cooler so that's not the issue. Idling for one minute at 1200 rpm allows the relatively cooler idle exhaust gases to cool the wheel quickly and prevent the rub. May gas turbines have similar issues and utilize more exotic solutions.

 

[DieselBound]

My NH manual specifically states it's to prevent rubs. As I stated previously, after running at full power for long periods, the turbine wheel is very hot and is at its max diameter. The outer case cools quicker with the ambient air and it literally shrinks to a diameter that will cause a rub if you chop the throttle and shutdown. The bearings are running in oil which is cooled by a cooler so that's not the issue. Idling for one minute at 1200 rpm allows the relatively cooler idle exhaust gases to cool the wheel quickly and prevent the rub. May gas turbines have similar issues and utilize more exotic solutions.

There should NOT be issues associated with tolerances with the case and the turbine under normal operating conditions. If this is a concern then they're not engineered correctly. Yes, housing contact IS the path to utter failure. These things nearly always occur due to tolerance problems with the turbine shaft and bearing, and these problems can occur for several different reasons:

Failure-Diagnosis

Garrett has a nice chart showing all the reasons for problems (and nowhere does it mention concerns with turbine wheels rubbing casing due to not allowing turbine to cool; none of their "solutions" mentions needing to allow the turbine time to cool down):

https://turbobygarrett.com/turbobygarrett/sites/default/files/Garrett_Troubleshooting_Guide.pdf

I've got cars running more complex turbos -VNTs- and these have no such issues as a first failure point (rubbing ONLY occurs as a secondary issue, after the turbo is basically needing to be replaced [at a minimum the CHRA]).

All said, when going to stop an engine it's still a good idea to allow the turbo to cool a bit after running hard. If you note above, however, the origins of a lot of the problems lie elsewhere (even a bigger issue with proper management/care when cold).