Turbo bearings / ESS question

[OldBlue]

First off, I could not find any info on this, so if it's been asked and answered already, I apologize in advance!

My question revolves around turbo bearings and ESS. Your turbo has been spinning fast as you've been on the loud pedal for a bit. Now you come to a stop and ESS shuts off your engine. Your bearings are screaming as the oil they are depending on begins to boil... or at least get d@mn hot. Over time your turbo bearings start to scream in protest...

Does this happen? Is this/could this be an issue?

Normally I run w/ ESS disabled on my 3.6, but wifey has the 2.0 turbo w/ ESS and she does not shut ESS off. Just makes me wonder if I shouldn't use a Tazer or some other means of shutting off ESS. Personally, I find the system to be of little value. YMMV. Not sure if I'm overthinking the whole thing of if it could become an issue at some point.

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[BDinTX]

Personally, I find the system to be of little value.

100% agree with this. I watched a video testing out the claim that ESS can save fuel and reduce emissions. The test engine was smaller, 1.2L or so, and his results showed that the engine would have to be off for longer than 7 seconds to achieve savings.

Starting the engine requires a larger bump of fuel than maintaining idle. I believe this is especially true for diesel since they have extremely lean fuel requirements at idle. He also pointed out that down time would have to be longer for larger engines because even more fuel would be required for the restart.

So I started counting when ours shut down and rarely did I have an ESS event last even 7 seconds. So I try to remember to turn it off now, I’m just not willing to spend money to do it.

As to your scenario, I would be surprised if they didn’t take temperatures into account.

 

[Tethmes]

While i'm sure it will contribute to a very small amount of wear and tear over years, modern turbos are designed with this use in mind. Gone are the days of dropping a turbo in your civic in the 90s and making sure you sit at idle for a couple minutes before shutting off the engine.

 

[Chupacabra]

Or you can wait for for one (or both) of your batteries to weaken a bit and ESS will magically stop working forever...

 

[OldBlue]

Or you can wait for for one (or both) of your batteries to weaken a bit and ESS will magically stop working forever...

I already installed the ESS bypass jumper on my 3.6, hers will eventually get it too.

 

[Headbarcode]

On a turbo that uses the engine oil for lubrication and cooling of the center bearing, its best to let it idle and continue circulating oil after a spirited drive. This allows the turbo bearing time to cool down. Otherwise, the hotter bearing would cook of the liquid elements of the oil and the remaining hard elements would become the carbon buildup we'd like to avoid. Carbon is highly abrasive to machined parts like bearing races. Oil boiling is also known as "coking"

Our turbos are still lubricated with engine oil, but a dedicated antifreeze cooling circuit has been integrated into the center bearing housing. Antifreeze is far more efficient than oil when it comesbto absorbing and rejecting heat. Also worth mentioning, is that synthetic engine oil is vasting more resistant to coking compared to fossil engine oil.

During high heat shutdowns, the cooling circuit pumps are programmed to continue running. I just can't remember if it's on a timer or a thermistor set to a target low point.

 

[OldBlue]

On a turbo that uses the engine oil for lubrication and cooling of the center bearing, its best to let it idle and continue circulating oil after a spirited drive. This allows the turbo bearing time to cool down. Otherwise, the hotter bearing would cook of the liquid elements of the oil and the remaining hard elements would become the carbon buildup we'd like to avoid. Carbon is highly abrasive to machined parts like bearing races. Oil boiling is also known as "coking"

Exactly, and the whole reason for my posting.

Our turbos are still lubricated with engine oil, but a dedicated antifreeze cooling circuit has been integrated into the center bearing housing. Antifreeze is far more efficient than oil when it comesbto absorbing and rejecting heat. Also worth mentioning, is that synthetic engine oil is vasting more resistant to coking compared to fossil engine oil.

During high heat shutdowns, the cooling circuit pumps are programmed to continue running. I just can't remember if it's on a timer or a thermistor set to a target low point.

THAT'S the part I was unaware of, and the reason for my question. I 'assumed' that there would be SOME thought put to this by the engineers since when the engine stops, the flow of oil to the turbo would also stop. Would they have an external electric pump to continue to supply oil to the bearings during an ESS event, would there be some different kind of cooling involved, etc. How would they manage it. Thanks for the response.

 

[Headbarcode]

Exactly, and the whole reason for my posting.



THAT'S the part I was unaware of, and the reason for my question. I 'assumed' that there would be SOME thought put to this by the engineers since when the engine stops, the flow of oil to the turbo would also stop. Would they have an external electric pump to continue to supply oil to the bearings during an ESS event, would there be some different kind of cooling involved, etc. How would they manage it. Thanks for the response.

You're here for answers not guesses, so let me start by saying that I'm not familiar with the lubrication and cooling systems that intimately. I do know that we have a dual stage electric oil pump, but I don't know if it stays powered during stop/start events to maintain oil pressure. I'll assume that it's not variable with output pressure because it's referred to as dual stage. Watching the oil pressure gage during a stop/start event, that is long enough for bleed down, would answer that.

I know the turbos antifreeze circuit is much more efficient and quicker to pull down temps than solely relying on engine oil. It's efficiency probably doesn't allow the bearing to hit as high of temps, and if it does, it'll be absorbed by the time you pull up the driveway and put it in park. I know the cooling pump will continue running after a hotter shutdown or during a stop/start event. What I don't know is if it's set to a timer or a target pull down temp. I also don't know what volume per minute it runs or if that's fixed or variable.

Truthfully, my biggest concern is the repeated loss of oil pressure to the furthest reaches, which are all the oil galleys under the valve covers. Synthetic oil creates a molecular bond to hard parts, so there's always a film of oil present, but that same volume of oil is still responsible for cooling.

The easiest answer is using a Tazer, or the like, to keep the engine running.

 

[AnnDee4444]

Starting the engine requires a larger bump of fuel than maintaining idle.

This might not be true for eTorque equipped motors. The BSG spins the engine up much closer to idle RPM than a tradiditional starter.

I do know that we have a dual stage electric oil pump, but I don't know if it stays powered during stop/start events to maintain oil pressure.

It doesn't. You can see the oil pressure gauge drop to zero when the motor shuts off for ESS.

 

[AnnDee4444]

It doesn't. You can see the oil pressure gauge drop to zero when the motor shuts off for ESS.

I should also add that this assumes only one oil circuit (which I can't confirm or deny). If the turbo is on it's own circuit, it might not be monitored by the oil pressure gauge.

 

[BDinTX]

@AnnDee4444 Fair point. - I'm pretty sure his test case didn't have eTorque, I think it was a small import sedan.

 

[Old Dogger]

Protecting your turbo from excessive temperature damage
There’s no real secret to protecting your turbo from the risk of excessive temperature damage, essentially, it comes down to common sense and good vehicle maintenance:

• Look after your oil – regularly check your oil levels, and always keep your engine topped up with high quality oil that meets the specifications of your vehicle
• Regular maintenance and servicing – have your vehicle serviced regularly, in line with the manufacturer’s recommendations
• Drive carefully – let your engine warm up before pushing it too hard, and let your turbo ‘spool down and cool down’ for 5-10 seconds before switching off your engine after every journey
• Don’t leave it to chance – if you notice any of the symptoms outlined in this blog, have your engine and turbo checked by a competent, reputable mechanic. Turbo problems aren’t going to solve themselves, and the longer you leave a problem, the more damage will be caused, making it a more expensive fix.
• Be sensible with your mods – If you are making any modifications to your engine or ECU, make sure you know what you are doing. Trying to push things too far, or altering settings beyond your engine tolerances is a recipe for disaster!

 

[jjvincent]

I bet the turbo will outlast the Jeep. In this day of age, turbos do not fail like when I first started seeing them back in the 70's. When they were common in the 80's, there were failures all of the time. Since then, the life of turbos has got much better. I claim it's because we learned from the old days and now make better turbos. You also have to remember that many sedans and SUV's have turbos on them. Trust me, 95% of them are not treated well at all yet they go 300K with zero turbo issues. It's usually the rest of the vehicle is wore out and they unload it.

Plus, ESS has been used in Europe for years and many of them are turbo too (diesel and gas). So far I don't hear about turbo issues there either.

If you want to worry, then you need to about the plastic parts for the cooling system. Hopefully Jeep did not use the same supplier that GM uses for the Cruz. Because those things are failing at an alarming rate when they hit 5 years old. I'm really good at working on them but feel bad for the customers as it's one thing after another. Top it off, then it's the plastic for the valve covers and various vents. I do know that Jeep wiring harnesses do not age well either. So get ready for that.

 

[Headbarcode]

I should also add that this assumes only one oil circuit (which I can't confirm or deny). If the turbo is on it's own circuit, it might not be monitored by the oil pressure gauge.

I would hope that the turbo is on its normal loop with the rest of the engine, that way the pressure gage is monitoring all things engine oil related. It only makes sense for it to have its own cooling loop.

 

[AnnDee4444]

I would hope that the turbo is on its normal loop with the rest of the engine, that way the pressure gage is monitoring all things engine oil related. It only makes sense for it to have its own cooling loop.

It wouldn't surprise me... an eTorque equipped Jeep has at least a coolant circuit and an electrical circuit (48V) that the driver has no way of monitoring.

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