Leave engine running?

[GrizBota]

I dont think any of this is news to you

That condition is called the mixed mode regime. In a journal bearIng you want to maintain a full hydrodynamic regime where HMIN is never less than the height of the asperities and there is no metal to metal contact.

HMIN is largely dependent on the radial loading on the journal, the rotational surface speed of the journal relative to the bearing, diametral bearing oil clearance, and the dynamic viscosity of the oil.

Slow engine down HMIN decreases and you get boundary conditions

Thin oil out with heat or loss due to hydrodynamic shear force HMIN decreases.and you get boundary conditions.

Lug (load) engine up at low RPM HMIN decreases and you get boundary condtions.

And the nail in the coffin. Over tine bearing clearances inevitably increase with wear, HMIN decreases during nornal operation, boundary and mixed mode lubrication begins to occur more frequently, and the rate of bearing wear accelerates.

Dan

Your explanation(s) of it is one of the best I’ve run across in a web forum discussion of the topic.

I’ll offer up to those that have a belief otherwise, that this explanation happens to be a mathematical model of the behavior. It’s not a faith based belief. So if math isn’t person’s thing, it’s ok, but the phenomenon described by the model will continue regardless of one’s belief in the model. E.g. planes will continue to fly and engines will continue to wear even if a person doesn’t understand why.

 

[fried1765]

Just you wait until the EPA mandates stop/ start in our tractors. My commuter car does that and I hate it!

Same issue here....and I hate it too

 

[GrizBota]

Same issue here....and I hate it too

Well, both of you guys are savvy enough to figure out how to bypass the stop/start circuit. Like your tractors, make it what you want.

 

[fried1765]

Well, both of you guys are savvy enough to figure out how to bypass the stop/start circuit. Like your tractors, make it what you want.

Nope.....not easily accomplished on my 2014 Mercedes E-350.

 

[GrizBota]

Nope.....a very iffy solution on my 2014 Mercedes E-350.

Agreed. Whether you think you can or can’t, you’re likely correct.

 

[The Evil Twin]

Well, both of you guys are savvy enough to figure out how to bypass the stop/start circuit. Like your tractors, make it what you want.

There are modules that one can buy already. Just haven't gotten around to it. The only time I think about it is the 1st time it does it. Then I hit the disable switch and forget. Lol!

 

[The Evil Twin]

Nope.....a very iffy solution on my 2014 Mercedes E-350.

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[GreensvilleJay]

I have a permanent solution to 100% prevent anyone from starting are driving away any 'start/stop' vehicle....

 

[TheOldHokie]

Your explanation(s) of it is one of the best I’ve run across in a web forum discussion of the topic.

I’ll offer up to those that have a belief otherwise, that this explanation happens to be a mathematical model of the behavior. It’s not a faith based belief. So if math isn’t person’s thing, it’s ok, but the phenomenon described by the model will continue regardless of one’s belief in the model. E.g. planes will continue to fly and engines will continue to wear even if a person doesn’t understand why.

Its also an observable phenomenon.

Nikolas Petrov is generally ctedited with the model. Beauchamp Tower made independent discoveries in the same area. In 1883, he published reports showing pressure measurements of a liquid film in a slip bearing. He accidentally discovered hydrodynamic pressure.

He also found that the local pressure of the liquid film is higher than the average pressure. Tower concluded that the pressure is constantly changing in a circumferential direction.



Mr Tower was just trying to design a bearing for railroad cars anf accidentally observed the unexpected pumping action in his experimental axle setup. That started him thinking and questioning.

Dan

 

[NCL4701]

This thread is reminding me why I started at NC State as a mechanical engineering major, interned with a large manufacturer in their engineering department for two summers, and ended up with a business degree.

 

[fried1765]

I have a permanent solution to 100% prevent anyone from starting are driving away any 'start/stop' vehicle....

I am not looking for a solution to prevent starting or driving.
I am looking for a solution to ALLOW me to drive the vehicle, without auto shutdown at every stop.

 

[hagrid]

Its also an observable phenomenon.

Nikolas Petrov is generally ctedited with the model. Beauchamp Tower made independent discoveries in the same area. In 1883, he published reports showing pressure measurements of a liquid film in a slip bearing. He accidentally discovered hydrodynamic pressure.

He also found that the local pressure of the liquid film is higher than the average pressure. Tower concluded that the pressure is constantly changing in a circumferential direction.



Mr Tower was just trying to design a bearing for railroad cars anf accidentally observed the unexpected pumping action in his experimental axle setup. That started him thinking and questioning.

Dan

Did Beauchamp have any children named Eiffel?

 

[BruceP]

Do you leave your Kubota diesel tractor running when it may be 20 minutes or so before you will use it again?

This is a much-debated subject which is unlikely to be resolved here. There are a lot of variables which come into play.

Lets not forget that CONSUMING FUEL is not a big concern.... a diesel engine is VERY frugal while idling. Hence, our concerns may be more about the machine itself. (carbon buildup, wet-stacking...etc)

I would suggest 10 minutes is the longest I would keep engine idling. An un-attended machine can become a disaster. (burst into flames...etc)

There are some rules-of-thumb which may help:

• If cold engine was just started.... perhaps keep it running
  • Battery will not be fully re-charged for at least an hour of running
  • There is no need to double-drain the battery
  • You want some heat in the engine before loading it anyway.
• Does engine have exhaust-scrubber? (DEF injection)
  • If engine has not ran thru a cleaning lately... This may be a good time to kick off a 'manual' clean.
• After working engine hard, it is IMPERATIVE to allow some idle-time to cool the turbocharger-bearings. (owners-manual actually mentions this)
• Is the outside temperature below 40F?
  • Consider idling instead of another startup

 

[BruceP]

As for long periods of idling… one might also do a “search” on these forums about diesel “slobber”….and see how mischievous THAT problem can be due to long periods of low rpm.

Is 'slobber' another term for "Wet Stacking"?

 

[TheOldHokie]

This thread is reminding me why I started at NC State as a mechanical engineering major, interned with a large manufacturer in their engineering department for two summers, and ended up with a business degree.

I am a mathematician by training and the math is still mind numbing. For example there is no general solution to the Navier-Stokes equations. You have to fix one of the variables to obtain a partial solution for the others. An ungodly number of compute cycles have been expended on the problem and I had a personal hand in a few. I still skip over those sections in textbooks. I am never going to be asked to regurgitate them or formulate a similar solution.

The basic concept however is no more complicated than say elasticity of demand. You managed to wrap your head around that "model". This should be no more daunting.

Dan

 

[NCL4701]

The basic concept however is no more complicated than say elasticity of demand. You managed to wrap your head around that "model". This should be no more daunting.

Dan

The basic concepts discussed in the thread make perfect sense. Where it started to fall apart for me was when it got to (using this thread topic as an example), “Now that you have the basic concept, calculate the viscosity of multi-grade oil to spec for this specific engine.” And my response ended up being, “How about I interpret tax code, complex business contracts, and civil litigation instead?”

Much of what I dealt with in the real world of the manufacturer’s engineering department was more practical mechanics and having a working knowledge of material properties. Even then, when you could still buy a slide rule but scientific calculators were taking over, computers did most of the heavy lifting for working engineers, but not in the classroom. One of my projects for the manufacturer was specing out a $40 million total renovation of one of their smaller factories that hadn’t had a real facelift since the 1920’s. I realized toward the end of the project when a senior engineer reviewed my blueprints, specs, vendor quotes, and internal cost estimates that it was intended to be busy work to keep me from bothering them. It was one of my better moments when they reviewed everything I’d put together, said they were shocked at what I’d come up with and implemented my plans for the renovation. They gave me copies of the blueprints when I went back to school as a momento of doing something worthwhile. I still have them somewhere, but that was the end of my engineering career.

I was struggling with the integrals part of dynamics (integrals are still a black hole of mystery to me and probably not to you) and had an accounting course with an attractive female professor that took an interest in me, at least partly for my accounting abilities. Nothing beyond accounting happened with her because I found out she was married and that wasn’t cool with me, but she convinced me if engineering wasn’t working out, I could still do better than working for UPS at night and a tree service during the day. So I changed to business and haven’t regretted it.

The little bit of formal engineering and metallurgy training I did get combined with the business degree and a good bit of hands on mechanicing outside of formal education was very helpful in my career.

But I’m still not an engineer and don’t pretend to be one. Mad respect for those who made it into a career.

 

[TheOldHokie]

The basic concepts discussed in the thread make perfect sense. Where it started to fall apart for me was when it got to (using this thread topic as an example), “Now that you have the basic concept, calculate the viscosity of multi-grade oil to spec for this specific engine.” And my response ended up being, “How about I interpret tax code, complex business contracts, and civil litigation instead?”

Much of what I dealt with in the real world of the manufacturer’s engineering department was more practical mechanics and having a working knowledge of material properties. Even then, when you could still buy a slide rule but scientific calculators were taking over, computers did most of the heavy lifting for working engineers, but not in the classroom. One of my projects for the manufacturer was specing out a $40 million total renovation of one of their smaller factories that hadn’t had a real facelift since the 1920’s. I realized toward the end of the project when a senior engineer reviewed my blueprints, specs, vendor quotes, and internal cost estimates that it was intended to be busy work to keep me from bothering them. It was one of my better moments when they reviewed everything I’d put together, said they were shocked at what I’d come up with and implemented my plans for the renovation. They gave me copies of the blueprints when I went back to school as a momento of doing something worthwhile. I still have them somewhere, but that was the end of my engineering career.

I was struggling with the integrals part of dynamics (integrals are still a black hole of mystery to me and probably not to you) and had an accounting course with an attractive female professor that took an interest in me, at least partly for my accounting abilities. Nothing beyond accounting happened with her because I found out she was married and that wasn’t cool with me, but she convinced me if engineering wasn’t working out, I could still do better than working for UPS at night and a tree service during the day. So I changed to business and haven’t regretted it.

The little bit of formal engineering and metallurgy training I did get combined with the business degree and a good bit of hands on mechanicing outside of formal education was very helpful in my career.

But I’m still not an engineer and don’t pretend to be one. Mad respect for those who made it into a career.

If integration is a mystery look up the Rieman Sum as axway to understand what Integration ia doing. Integration of thatvfunction is just that Rirman sum when the number of sub divisions is infinite. That teacher was hot but had absolutely zero interest in me and she tested with problems that would have made a TI calcularor moan under the load. My slide rule (required for all physics majors) was absolutely worthless.

Dan

 

[WFM]

My uncles 2020 Outback has the start stop save a tree feature. He has to go thru two screens on his computer to shut it off.
I found a inline override switch thing that plugs into the wiring harness in the headliner. Plug and play. He loves it.
But in 2021 Subaru added a button on the dash like my Ford truck has. Push the button and nothing shuts off.

 

[The Evil Twin]

My uncles 2020 Outback has the start stop save a tree feature. He has to go thru two screens on his computer to shut it off.
I found a inline override switch thing that plugs into the wiring harness in the headliner. Plug and play. He loves it.
But in 2021 Subaru added a button on the dash like my Ford truck has. Push the button and nothing shuts off.

I actually just ordered one today. The earlier comments in this thread reminded me to do it. Never remembered until the car shut off. Ha!
The manufacturers only do that to up the EPA numbers they have to meet. They figure by the time the battery, starter or wrist pins take a dump, it'll be the customer's problem.

 

[NCL4701]

If integration is a mystery look up the Rieman Sum as axway to understand what Integration ia doing. Integration of thatvfunction is just that Rirman sum when the number of sub divisions is infinite. That teacher was hot but had absolutely zero interest in me and she tested with problems that would have made a TI calcularor moan under the load. My slide rule (required for all physics majors) was absolutely worthless.

Dan

Maybe if things go really poorly and I get stuck in a nursing home with my mind intact and my body falling apart I’ll delve back into the challenge. Until then…