Synthetic oil not only reduces CONCERNS..... it pretty much ELIMINATES oil-coking.
Machines with turbos- do you let them idle before shutting down
- Thread starter 243ackley
- Start date
Thanks for all the input guys. I never thought about the oil caking up. I always thought the issue was the turbo spinning without oil.
not saying that cool down is a bad idea, all the advise on this thread is accurate.... well except the tape over the exhaust when towing. BUT if you have ever been around standby EPG equipment, 90% of all standby gensets go to full governed rpm at key start, cold hot frozen whatever.... same as shut down! full rpm to stop. same as fire pumps and emergency dewatering pump engines, most all are large turbocharged engines and very few have turbo issues with 10000+ hours of some pretty extreme running conditions.
What you said is true, but our 150kw cat generator has a 5 minute cool down. It still runs at 1800 rpm, but no load for 5 minutes. I think the new controller is even longer.
BAP
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2012 Kubota 2920, 60MMM, FEL, BH65 48" Bush Hog, 60"Backblade, B2782B Snowblower
What exactly do you mean by tape over exhaust being wrong? What experience do you have hauling equipment?
I always put a turbo in idle, and sing “Happy Birthday” before I shut down...
Old habits die hard.
Turbos get hot to the point that the oil in the turbo vaporizes after shutdown,
causing the oil lines to coke and clog.
New turbos have coolant lines running through them, to prevent this.
I still wait a minute or two...
Use Shell Rotella T6 in 5W-40 or 0W-40, great oil...
Old habits die hard.
Turbos get hot to the point that the oil in the turbo vaporizes after shutdown,
causing the oil lines to coke and clog.
New turbos have coolant lines running through them, to prevent this.
I still wait a minute or two...
Use Shell Rotella T6 in 5W-40 or 0W-40, great oil...
not saying it wrong but the theory that the turbo can spin and burn the bearings up while dragging one down the road is a old wives tale, now even more so is it not feasible because of DPF/SCR in the exhaust stream blocking any thing resembling wind that might blow down a stack. the chances of a 4 stroke engine stopping with intake and exhaust valves open on the same cylinder at the same time is very remote. then the air has to go through a muffler, through a turbine wheel,through a exhaust manifold, through 2 valves that are barely cracked open, through a intake manifold, through a turbo compressor wheel, through a air filter and back out the airbox with enough velocity to spin a turbine shaft.
I dont have a ton of experience towing heavy equipment, what I do have is 15 years as a heavy iron repair tech, in the past 15 years I have not seen one turbo that the failure could be directly attributed to coking or wind milling, every one I have ever replaced was a wheel failure caused by over speed, or over heating caused by lack of air or to much fuel.
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Mike,
Your explanation is certainly plausible. However, eliminating old wives tales could cause a complete recalibration of the way many of us lead our lives, what's next, dismantling the urban legends?
Where is the excitement in practical theory if it is only supported w/ provable facts?
D2cat,
That reminds me, put Vicks on the shopping list.
Your explanation is certainly plausible. However, eliminating old wives tales could cause a complete recalibration of the way many of us lead our lives, what's next, dismantling the urban legends?
Where is the excitement in practical theory if it is only supported w/ provable facts?
D2cat,
That reminds me, put Vicks on the shopping list.
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Mike i appreciate your answer. It was complete, detailed and well explained. It also explains why you don't need to be a person who hauls a lot of equipment to answer the question...you see it after it's been hauled.
But like Majorwager said, some of those wives tales we don't want to give up. I still put Vicks on the bottom of my feet if I have a bad cold!!
But like Majorwager said, some of those wives tales we don't want to give up. I still put Vicks on the bottom of my feet if I have a bad cold!!
Running synthetic oil does not solve the turbo problem. Does it help because it can withstand more heat? Possibly. Does Kubota require or recommend synthetic engine oil? Nope. The problem is that the turbine wheel bearings on both the hot and cold side are lubed with engine oil. When your engine stops, the turbo remains spinning. It suddenly only has whatever residual oil is in the bearing housing to lubricate (and cool) it. Whether you run regular or synthetic oil makes no difference to the fact that pressurized oil suddenly stops flowing through your turbo bearings. Many older turbocharged road vehicles (and possibly tractors) had a prescribed method of allowing the vehicle to idle for a few minutes before shutting down. Some companies even made "turbo timers" which would automatically shut the engine off after a set amount of time. This is the cause for the "old habits" we see here. Modern turbos use more efficient methods of controlling heat...better bearing materials, such as ceramic, inconel, etc. help, along with using water cooling in addition to just oil. Oil passageways tend to be better designed as well. Some modern road vehicles use a small electric water pump which pumps in reverse when the engine is off, to draw cool antifreeze from the radiator and push it through the turbo to help cool the residual oil. Most turbo engines now use coolant and take advantage of natural convection flow to cause a cooling effect to the turbo.
Engines with a DPF do not "run hotter," that is nonsense. Engine coolant and oil temps would run similarly to other non-DPF engines. Larger radiators and oil coolers are in place to combat additional ambient heat load under the hood occurring during a regeneration or because of turbocharging.
Do modern Kubota tractors with a turbocharger use liquid cooling on their turbos, or simply oil? I really don't know if they do or not. My MX4800 is the non-turbo model.
Certainly idling the engine for a minute or two, especially after full-throttle application, will not harm anything. But there may be plenty of times it is unneeded. I don't recall if the Kubota manual gives any advice to idle or not.
Engines with a DPF do not "run hotter," that is nonsense. Engine coolant and oil temps would run similarly to other non-DPF engines. Larger radiators and oil coolers are in place to combat additional ambient heat load under the hood occurring during a regeneration or because of turbocharging.
Do modern Kubota tractors with a turbocharger use liquid cooling on their turbos, or simply oil? I really don't know if they do or not. My MX4800 is the non-turbo model.
Certainly idling the engine for a minute or two, especially after full-throttle application, will not harm anything. But there may be plenty of times it is unneeded. I don't recall if the Kubota manual gives any advice to idle or not.
Troverman,
I do not know specifically if DPF engines operate at higher normal temps. I do not own a DPF engine.
I do know that my MX barely moves the temp gauge in the winter. I also believe DPF engines employ a higher temp water thermostat.
I would suggest that members w/ DPF engines use a non- contact laser thermometer to determine their engine temps under no load high idle conditions.
I would do the same and compare. My turbo boost is minimal since the engine is not rated much higher than yours. It is only oil lubricated, no coolant piping.
Wives Tales, of either the old or new variety, not likely to disappear soon, the internet grows that list daily.
It seems logical that activating the regen cycle from an already hotter engine operating temp, would be easier to accomplish.
I have an IH D-179 engine that never exceeds 160 degrees w/ mechanical temp guage. Doubt any Kubota DPF engine sees operating temps in that low range.
I do not know specifically if DPF engines operate at higher normal temps. I do not own a DPF engine.
I do know that my MX barely moves the temp gauge in the winter. I also believe DPF engines employ a higher temp water thermostat.
I would suggest that members w/ DPF engines use a non- contact laser thermometer to determine their engine temps under no load high idle conditions.
I would do the same and compare. My turbo boost is minimal since the engine is not rated much higher than yours. It is only oil lubricated, no coolant piping.
Wives Tales, of either the old or new variety, not likely to disappear soon, the internet grows that list daily.
It seems logical that activating the regen cycle from an already hotter engine operating temp, would be easier to accomplish.
I have an IH D-179 engine that never exceeds 160 degrees w/ mechanical temp guage. Doubt any Kubota DPF engine sees operating temps in that low range.
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Majorwager, your tractor isn't DPF-equipped? Or was it just made before the regs hit?
Hotter EGT indeed helps a regen. That's why pickups with diesels have to regenerate less if they are being worked hard...e.g. towing heavy loads. But that is based upon EGTs, not engine water and oil temps. My B2920 and L4310 also don't heat up much...when its cold, they barely move the needle off the cold mark. In summer, while field mowing, I've had them both come close to overheating because of plugged radiator cores (grass chaff getting past the screen). I don't believe any of the non-electronically controlled tractors use a thermostat...but the ones with common-rail direct injection do. There is an optimal water temp for the engine to be at, and I suspect it is near 200 degrees. But that is no different than a gas-powered car or diesel truck.
The DPF is completely post-engine, so the only added heat load would be due to the fact that it is located under the hood on top of the engine. That could passively heat the engine block and increase oil and water temps. That's why I suspect the cooling system has been beefed up to accommodate that fact. I also believe my MX4800 has cooled EGR. I haven't taken the side panels off completely yet to inspect, but it appears so.
Hotter EGT indeed helps a regen. That's why pickups with diesels have to regenerate less if they are being worked hard...e.g. towing heavy loads. But that is based upon EGTs, not engine water and oil temps. My B2920 and L4310 also don't heat up much...when its cold, they barely move the needle off the cold mark. In summer, while field mowing, I've had them both come close to overheating because of plugged radiator cores (grass chaff getting past the screen). I don't believe any of the non-electronically controlled tractors use a thermostat...but the ones with common-rail direct injection do. There is an optimal water temp for the engine to be at, and I suspect it is near 200 degrees. But that is no different than a gas-powered car or diesel truck.
The DPF is completely post-engine, so the only added heat load would be due to the fact that it is located under the hood on top of the engine. That could passively heat the engine block and increase oil and water temps. That's why I suspect the cooling system has been beefed up to accommodate that fact. I also believe my MX4800 has cooled EGR. I haven't taken the side panels off completely yet to inspect, but it appears so.
Troverman.
Another point. My turbo does continue to spin with engine shut down. The duration is very short.
Mike, earlier post, explains. The air pressure generated by the turbo has nowhere to go. There is immediate resistance. Valves are closed, so backpressure causes the impeller to stop because it can't overcome said resistance.
So continued oil circulation is moot. The residual oil does encounter turbo heat, and for my investment, it shall be a synthetic bath.
Saying that kubota does NOT recommend synthetic crankcase lubricant is disingenuous. They do NOT restrict its' use either. They merely state the mineral based oils meet their minimum requirements.
In fact, UDT is now UDT2 and full synthetic, engine oil likely NOT far behind.
We are each individually responsible for the engine health of our tractors, my practices will error on the side of caution, applicable wives tales not withstanding.
EDIT: EGT? Do you mean EGR? Mine has common rail, high pressure, and EGR, NO DPF, Engine HAS coolant thermostat. Low sulfur fuel required but the limit is 500 PPM, NOT the DPF spec.
TROVERMAN,
True turbo impeller spins fast, however it is driven by exhaust thrust. Consequently, an idling engine is making very little exhaust pressure. This is why turbo spool up and whine when engine is accelerated. Gonna listen w/ stethoscope, but post shut down spin cycle is really short.
And think about your argument. Synthetic offers greater change intervals. TRANSLATION: Synthetic provides greater protection from heat, therefore maintains viscosity longer, exactly what is desired to protect the turbo. Actually the turbo on my MX is minute, and the air volume of exhaust from 148 cu. in. engine is rather insignificant, unit never seems very hot, gonna check the temp w/ laser thermometer to determine the average reading.
Not aware of Kubota 50 hr revision. Would like to hear from a 2017 or 18 owner, wherein the manual states filters only for hydraulic oil at 50 hours.
Another point. My turbo does continue to spin with engine shut down. The duration is very short.
Mike, earlier post, explains. The air pressure generated by the turbo has nowhere to go. There is immediate resistance. Valves are closed, so backpressure causes the impeller to stop because it can't overcome said resistance.
So continued oil circulation is moot. The residual oil does encounter turbo heat, and for my investment, it shall be a synthetic bath.
Saying that kubota does NOT recommend synthetic crankcase lubricant is disingenuous. They do NOT restrict its' use either. They merely state the mineral based oils meet their minimum requirements.
In fact, UDT is now UDT2 and full synthetic, engine oil likely NOT far behind.
We are each individually responsible for the engine health of our tractors, my practices will error on the side of caution, applicable wives tales not withstanding.
EDIT: EGT? Do you mean EGR? Mine has common rail, high pressure, and EGR, NO DPF, Engine HAS coolant thermostat. Low sulfur fuel required but the limit is 500 PPM, NOT the DPF spec.
TROVERMAN,
True turbo impeller spins fast, however it is driven by exhaust thrust. Consequently, an idling engine is making very little exhaust pressure. This is why turbo spool up and whine when engine is accelerated. Gonna listen w/ stethoscope, but post shut down spin cycle is really short.
And think about your argument. Synthetic offers greater change intervals. TRANSLATION: Synthetic provides greater protection from heat, therefore maintains viscosity longer, exactly what is desired to protect the turbo. Actually the turbo on my MX is minute, and the air volume of exhaust from 148 cu. in. engine is rather insignificant, unit never seems very hot, gonna check the temp w/ laser thermometer to determine the average reading.
Not aware of Kubota 50 hr revision. Would like to hear from a 2017 or 18 owner, wherein the manual states filters only for hydraulic oil at 50 hours.
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BAP
Well-known member
Lifetime Member
Equipment
2012 Kubota 2920, 60MMM, FEL, BH65 48" Bush Hog, 60"Backblade, B2782B Snowblower
It’s NOT Air Pressure that makes a Turbo spin going down the road with the engine not running, it is the Venturi effect of air blowing over the end of the exhaust pipe causing suction that gets the turbo spinning. As far as wives tales go, if your pocketbook is deep enough to risk damaging your turbocharger hauling or you confident enough that you won’t have problems and don’t want to spend 10-15 seconds putting a shop rag in the exhaust or tape over the end, then go for it.
Majorwager, the intake valves will never *all* be shut together. So while there will be some restriction, it will not be complete. Turbos spin incredibly fast. It is a relatively short period that they spin after the engine is off, but long enough to create a problem.
As for synthetic Super UDT, that move was for longer maintenance intervals. Kubota calls for a filter change after an initial 50 hours. Very expensive to have to change 15 gallons of hydraulic fluid after 50 hours, so with synthetic the intervals are longer and the initial change is just the filter.
As for synthetic Super UDT, that move was for longer maintenance intervals. Kubota calls for a filter change after an initial 50 hours. Very expensive to have to change 15 gallons of hydraulic fluid after 50 hours, so with synthetic the intervals are longer and the initial change is just the filter.
the air to spin a turbine has to come from somewhere!! LOL the 10-15 second spin down on a turbo is pretty insignificant compared to other high speed high heat IC engines.. P&W FT4-A turbines in the last ship I was on in the USCG took over 10 minutes to stop spinning, it did so with 0 lube oil pressure (pump driven off N2) and on journal bearings.
also to futher drive my meaningless point home even further, I have seen a tail wind sitting in port in Alaska howl down the stacks at well over 100MPH and never once did that jet engine even hint that it would try and turn!!!!! when I say howl, when you opened the intake plenum door it would blow open from the air rushing through the turbine!!! and it is a true axial flow turbine that is 10x's more efficient than the centrifugal turbine on these turbos were talking about.
I think it's a good practice to let any engine driven equipment idle for 5 minutes or so after being worked hard prior to shutting down. Lawn mower, generator, tractor, turbo truck, whatever.
Allegedly, the water cooled turbos on my 2011 F150 Ecoboost engine can be shut down immediately after driving. The rumor is that the coolant continues to flow via thermosiphon after the engine is shut off.
I still let my truck idle for a few minutes after normal driving and for ten minutes after towing.
Allegedly, the water cooled turbos on my 2011 F150 Ecoboost engine can be shut down immediately after driving. The rumor is that the coolant continues to flow via thermosiphon after the engine is shut off.
I still let my truck idle for a few minutes after normal driving and for ten minutes after towing.
That is true...convection-effect circulation. There are probably more than a million EcoBoost trucks on the road today, let alone all the other turbo vehicles. I'd bet less than 5% of drivers allow their turbos to cool.
A. Venturi effect on the exhaust pipe produces NO measurable pressure at the turbo and certainly not enough to make it spin. This is a myth and complete misunderstanding of a turbo and the physics of pressure. If you think it does please provide a reference supporting your belief. Physics, its not just a good idea its the law. Next question: What operating condition allows you to go down the road without the engine running?
B. Synthetics do help, as the base stock cokes at higher temps than dino based oils. However according to mobil 1, there is still a risk that when the oil stops moving through the turbo, i.e. shutdown, that some of the friction modifiers and stabilizers can coke, causing deposits. Ultimately, according to most oil manufacturers and several academic papers, the best way to prevent coking issues is to let the turbo cool under engine idle, to less than about 300 degrees. No, bs, no myth, no strange voodoo. If you want to protect your turbo, it has to be shut down at a temp below the coking temp for the oil your using.
B. Synthetics do help, as the base stock cokes at higher temps than dino based oils. However according to mobil 1, there is still a risk that when the oil stops moving through the turbo, i.e. shutdown, that some of the friction modifiers and stabilizers can coke, causing deposits. Ultimately, according to most oil manufacturers and several academic papers, the best way to prevent coking issues is to let the turbo cool under engine idle, to less than about 300 degrees. No, bs, no myth, no strange voodoo. If you want to protect your turbo, it has to be shut down at a temp below the coking temp for the oil your using.
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