Engine Lube Model - Sump Oil Temp Prediction

[Shannow]

re...
Engine Lube - Sump Temperatures - Article Review
https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=637273

The original post is locked for replying (while others of the era are open), and have been the topic of some discussion of late, I thought that I'd re-open it, thus the new thread.

Will start with the reference list, as they are the prior works that the authors reference in the paper.
http://papers.sae.org/710205/
http://papers.sae.org/2000-01-0284/
Google Search for Paper 3 - no link to genuine paper found, referred to in quite a few.
http://papers.sae.org/931157/
http://papers.sae.org/750080/
http://papers.sae.org/770032/
http://papers.sae.org/970637/
Google Search for Paper 9
http://pic.sagepub.com/content/208/3/199.abstract
http://papers.sae.org/740307/ (interesting and topical, also on the apparent problems with 10W40 in GM engines back in the day).
http://papers.sae.org/931139/

 

[Shannow]

Paper is 2001, and a bit interesting in how it's put together.

The premise is that engine architecture is designed, then it's not until the package becomes dyno tested that the whole shooting match comes together and the actual performance of the package is understood, by which time it's too late, and remedial action having to be taken. The modelling was intended to determine the heat sources TO the oil, and paths of dissipation FROM the oil, the nett result being sump temperature.

Strange in that they discount piston friction from their analysis "of oil heat gain", while acknowledging that the heat generated was commensurate to piston crown conduction, but was neglected as being in the skirt/ring area, it went straight into the coolant...

Further, the 2,000RPM "road load" sump temperature was seriously underestimated by the model, which the authors described as a "misunderstanding of the heat transfer" between the combustion gasses, piston crown, and oil.

Given that 24% of the "rest" went in the same direction, there are two ways of considering the skirt friction. Either:
* the total heat to oil at 4,000RPM was 22KW (versus 14.1 with skirt friction discounted), and 11.4 went straight into the coolant adjacent to the bore...making the piston contribution 46 ; or
* They could have netted off the skirt area heat transfer before it got in the vicinity of the sump (exactly the same as the skirt friction itself), and declared the heat transfer from the piston TO the sump heat as 48% of the Nett.

They have Netted a resultant off mid-way through the calculation, which is a bit unusual in a technical sense where they are summing the INPUTs, and Subtraction the OUTPUTs...

Per the original review of the article, quote from the paper
Quote:
One should not conclude that piston-bore friction is not important, or is missing from this analysisfrom the fact that the energy transfer to the oil from piston-bore friction is not a significant source of energy into the oil. The energy generated by piston-bore friction used in the study was 8KW (for the entire engine). This energy transer rate is of the order of the piston undercrown energy transfer rate to the oil. However, the piston-bore friction energy transfers into the engine metal structure and not directly to the oil as discussed previously.


Can't have the cake (oil temp inputs versus outputs), and eat it to (that part of the cake went missing).

Just needs to be considered when considering the "72%" factor.

 

[Shannow]

Established (through modelling and testing) a linear (for the engine in question) correlation of 0.7C change in oil temperature per 1C change in coolant temperature.

Similarly model predicted 0.25C change in oil temp per degree in ambient (they modelled sump and rocker cover heat dissipation)... the suggestion was that installing an engine in an engine bay with a local ambient of 50C, versus a dyno run in free air would increase sump temperatures by 7.5C.

In connection with the discounting of piston skirt friction above, that cutting the cooling jacket to 60% of the vertical height (deck to bottom of stroke) increased sump temps by 15C (see why it shouldn't have been netted off ???) while piston and ring temperatures increased by 33 and 43C respectively.

Model predicted 4C decrease in sump temperatures with Al block, but also stated that they (Ricardo) have not seen that in practice.

 

[Shannow]

As to where the heat GOES ... the heat sinks...biggest was the piston skirt to bore interface as described a couple posts ago.

Quote:
The energy Transfer to coolant occurs by connection TO the engine metal...
.
.
The bore walls and the oil deck in the head are typically the two most important areas to consider within the engine structure


So clearly the heat flow is FROM the oil TO the metal in these regions, and then into the coolant.

For the 4,000WOT example, the biggest "absorbers" of oil heat, with transfer TO the coolant were
* Lifter area (the valley area), as I described in the other thread, water jacket on one side, much surface area, a lot of heat gets to the coolant that way...18% of total.
* Camshaft housing 14%...remember, that's absorbing heat and transferring it to the coolant.
* Oil galleries 6%...again, heat FROM oil TO coolant through these.
* Timing Cover - 4%
* Rocker Covers - 4%

Leaving the Pan to deal with dissipating 27% of the thermal load (40% at the 2,000RPM WOT point)...3.81 versus 2.88KW respectively.

So the heat within the oil is COOLED by every surface that it is in contact bar the active heat sources (Pistons, Mains and Bigs, Oil Pump, and Cam bearings)

 

[ZeeOSix]

To spin back around to the discussion about engine load vs sump oil temperature, the one SAE paper you linked (http://papers.sae.org/740307/) shows pretty clearly that as engine load keeps increasing at a constant speed (causing the coolant system to work overtime) means the extra heat of combustion needs to go somewhere. Therefore the oil temperature goes up significantly with ever increasing engine load (more combustion, more HP) at a constant speed/RPM as Figure 2 below shows. This also correlates with the anecdotal examples I posted of guys pulling heavy trailers up long steep hills with their trucks. Of course, the better the cooling system, and most importantly the use of an effective oil cooler will really help keep the sump oil temperature down.

 

[Shannow]

You accused me of "cherry picking" in previous threads and then come out with that ???

I'd suggest that anyone reading the thread go to the linked paper, and interpret for themselves whether you are genuinely conveying the information in that paper, or suffer seriously from confirmation bias...

 

[ZeeOSix]

Originally Posted By: Shannow
You accused me of "cherry picking" in previous threads and then come out with that ???

I'd suggest that anyone reading the thread go to the linked paper, and interpret for themselves whether you are genuinely conveying the information in that paper, or suffer seriously from confirmation bias...


For starters, it wasn't me that accused you of "cherry picking". Go back and get it straight. Memory Jog - Nickdfresh quoted (11/06/16 08:25 AM) in the Vette thread about your postings: "Yup, cherry-picking modus operandi..."

And besides, I clearly gave the source of the Figure 2 graph above, so anyone can see the same exact thing I do, and read it all for themselves.

Now what's not to understand about the graph? Pretty simple ... increase the load on the engine by towing heavier and heavier loads maintaining the same speed (meaning it takes more throttle and more HP), and the cooling system AND the oil will increase in temperature. In fact, if there is no oil cooler or the cooling system really lacks performance, then the oil will just keep getting hotter and hotter until bad things happen with lubrication (ie, death spiral mentioned in the Vette thread).

And don't say what's happening in Figure 2 is all because they had to shift down and rev the engine 3 times as high. There is nothing in the text or graph that eludes to any transmission downshifts or increase in engine RPM at those road speeds. They would have clarified that given that they understand that RPM alone will also increase oil temperature as talked about in the paper and shown in Figure 1.

Don't tell me you really think all that temperature increase shown in Figure 2 is all due from just the journal bearing RPM, even when increased engine loads occur at a constant RPM/speed, and that the cooling system absorbs 100% of every extra joule due to increased throttle openings and no extra heat goes into the oil - LoL.

Guess that goes along with believing journal bearings don't flow any extra oil when pressure fed.

The "No Trailer" case in Figure 2 is their minimum engine load baseline, and is essentially the little test you did with your car. Now go do some testing while pulling different loads around and get back with the data, and you'll see that your oil temperatures will also increase similar to what's shown in Figure 2 as more HP is being put out by the engine at the same engine PRM/road speeds.

 

[Shannow]

Originally Posted By: ZeeOSix

Don't tell me you really think all that temperature increase shown in Figure 2 is all due from just the journal bearing RPM, even when increased engine loads occur at a constant RPM/speed, and that the cooling system absorbs 100% of every extra joule due to increased throttle openings and no extra heat goes into the oil - LoL.

Guess that goes along with believing journal bearings don't flow any extra oil when pressure fed.

There you go again, presenting false arguments as my position...you are good...and predictable.

What did figure 1 show ?

The one on same road speed (load) with different gearing ?

Linear with load (manifold pressure), exponential with RPM ?

 

[ZeeOSix]

Originally Posted By: Shannow
Originally Posted By: ZeeOSix

Don't tell me you really think all that temperature increase shown in Figure 2 is all due from just the journal bearing RPM, even when increased engine loads occur at a constant RPM/speed, and that the cooling system absorbs 100% of every extra joule due to increased throttle openings and no extra heat goes into the oil - LoL.

Guess that goes along with believing journal bearings don't flow any extra oil when pressure fed.

There you go again, presenting false arguments as my position...you are good...and predictable.

What did figure 1 show ?

The one on same road speed (load) with different gearing ?

Linear with load (manifold pressure), exponential with RPM ?


Not a "false argument", but rather a perception of how you come across in these discussions. That's what you believe right - that there is no real heat load into the oil from the heat of combustion? That's how you keep coming across because you've never believed my position that engine load certainly does play a large roll in sump oil temperature. That's the main reason you even started this discussion again.

Analyze it again. Figure 1 is one car only (Car A) and no trailer pulling, but only looking at different rear end gearing so they could see the impact of increased engine RPM at road speed on oil temperature. Figures 2 & 3 are both for the same car (Car B) with same gearing, and the those two graphs correspond with the same trailer pulling tests ... they don't correspond with anything in Figure 1.

Figure 2 clearly shows there certainly is a strong correlation between engine load and sump oil temperatrue. Keep in mind that the family of curves will be different for basically every car on the road depending on how the oil gains and rejects heat under different engine loads. I'm sure the cars they used back in the early 70s for this testing didn't have any oil cooler, and probably had a marginal cooling system at best.

 

[Shannow]

Originally Posted By: ZeeOSix
Not a "false argument", but rather a perception of how you come across in these discussions. That's what you believe right - that there is no real heat load into the oil from the heat of combustion? That's how you keep coming across because you've never believed my position that engine load certainly does play a large roll in sump oil temperature. That's the main reason you even started this discussion again.


No, that's NOT what I believe, I have always maintained that it's a contributor for sure, but in my own experience and testing, the difference due to RPM alone at the same road load is massive...that's my point, is that RPM on the track is a bigger influencer than throttle opening (load).

But as usual, you are attributing a strawman argue onto me that I'm not arguing...yes, load increases temperature, but RPM more so.

And this thread is on my view on the linked paper (that I bothered to buy), not the version that you originally linked to, with erroneous conclusions, that you declared gospel.

Buy it and read it...that's the challenge that you set me...better still, buy the one that you are currently hanging your hat on, and post the conclusions...

 

[ZeeOSix]

Originally Posted By: Shannow
Originally Posted By: ZeeOSix
Not a "false argument", but rather a perception of how you come across in these discussions. That's what you believe right - that there is no real heat load into the oil from the heat of combustion? That's how you keep coming across because you've never believed my position that engine load certainly does play a large roll in sump oil temperature. That's the main reason you even started this discussion again.


No, that's NOT what I believe, I have always maintained that it's a contributor for sure, but in my own experience and testing, the difference due to RPM alone at the same road load is massive...that's my point, is that RPM on the track is a bigger influencer than throttle opening (load).


You never did a test with an significant load in order to open up the throttle substantially more to maintain engine RPM. Once you do that and post up the test results, then we can discuss further, but for now the discussion is pretty much at "merry-go-round" status. The testing in the SAE paper shows results of what happens to oil temperature when increased engine loads are used at constant speeds. Go try the test yourself if you don't believe the SAE paper.

I never said there wasn't significant heat input to the oil due to bearing RPM ... all I ever said is that heat of combustion due to increasing loads and required increased HP at a constant engine RPM could significantly add more heat, and hence an added rise to the sump oil temperature above what just bearing RPM results in. Figure 2 above shows exactly that ... no room for argument there, zero.

Originally Posted By: Shannow
But as usual, you are attributing a strawman argue onto me that I'm not arguing...yes, load increases temperature, but RPM more so.


Then why you are even arguing if you agree? I've never said RPM isn't a contributor, or have even tried to divide how much comes from where. But the fact is, oil temperature is also effected by how much combustion is going on. Again, all I've said is that ever increasing HP output (at the same engine RPM) is going to make the oil heat up even more (as shown in Figure 2 above). The increased in oil temperature could be significantly more depending on many factors. If anything, you're creating strawman arguments over things that aren't even directly related to the real focus of the discussion here.

There were many posts made by you in the Vette thread making it sound like you believed that high amounts of HP (combustion rate) would only add few more degrees to the oil temperature (go back and re-read that thread). I said it could be more than a few degrees, that it could be significant. It's clear that added heat to the oil due to increased combustion heat can be significant, as shown in this SAE paper and in Figure 2.

Originally Posted By: Shannow
And this thread is on my view on the linked paper (that I bothered to buy), not the version that you originally linked to, with erroneous conclusions, that you declared gospel.

Buy it and read it...that's the challenge that you set me...better still, buy the one that you are currently hanging your hat on, and post the conclusions...


Don't need to ... what's already been presented here shows exactly what I've been saying all along. At a constant engine RPM, more throttle --> more combustion rate --> more HP --> more heat --> hotter engine mass temp --> increased coolant temp --> increased oil temp. Simple basic heat transfer, add more heat than can be dissipated, and temps go up.

 

[Shannow]

http://wrap.warwick.ac.uk/3494/1/WRAP_THESIS_Fenton_1994_1.pdf

FLOW AND HEAT TRANSFER MODELLING OF AN AUTOMOTIVE ENGINE LUBRICATION SYSTEM

Volume I Marcus B. M. Fenton I Thesis submitted for the degree of Doctor of Philosophy Submitted to the University of Warwick June 1994 Advanced Technology Centre University of Warwick Coventry CV4 7AL

Complete paper at the link...plus it has pictures...

Quote:
Oil Temperature Observations The engine tests were carried out over an engine speed range of 2000 to 5000 rpm, and 1/4,1/2and 3/4full loads. The results showed that the rise in oil temperature, as expected, was more greatly influenced by higher engine speeds than by an increase in load. These trends are shown graphically in Figure 8.4 and Figure 8.5. Similar results were found by Hayashi (1969) and Andrews et al (1989). Both authors attributed the influence of the engine speed on the overall oil temperature to be primarily due to the increase in oil temperature within the bearings. The rise in temperature of the oil film in the bearings was a result of the increase in oil film shear at high rotational speeds.

 

[Shannow]

Originally Posted By: ZeeOSix
Not a "false argument", but rather a perception of how you come across in these discussions. That's what you believe right - that there is no real heat load into the oil from the heat of combustion? That's how you keep coming across because you've never believed my position that engine load certainly does play a large roll in sump oil temperature.


Just for completeness, here is my quote in the Corvette thread which you have construed the way that you are using it...I can't be much more clear in my position than...

Originally Posted By: Shannow
I have said that RPM is the dominant factor in oil temperature rise, and have never discounted load as a part factor...it's just not the MAJOR factor.


Which for some reason has you chasing me around the board, building a strawman argument that you attribute to me, and then trying to strike it down...

 

[Shannow]

http://papers.sae.org/2007-01-2531/

Quote:
Gruden; Kuper; Porsche [9]] describe the influence of fucntioning parameters on the heat transfer to the lubrication oil. The authors conclude based on a energy balance made in a test bench that the most important parameter is engine speed. The engine load has a not so strong influence. The art of the cylinder block construction showed no impact on the heat transfer percentage to the oil. Part of these results was confirmed by Sebesse et al [10]. The heat rate to the oil is showed in the figure 3 (as a function of the engine speed and load)


Figure 3 is included in the document preview.

 

[ZeeOSix]

Did I ever say engine load was the major factor and RPM wasn't? - the answer is no. I said engine loadcould be significant - depends on many factors. I think you're just arguing for the sake of arguing, even when you seem to agree you still argue with lots of departures into the weeds - I really think it's your favorite pastime. It's evident here (again) since you are arguing about something you already claim to agree with. So what's your point of argument here - the exact amount of heat added from combustion? The discussion is bit nonsensical at this point because there is no specific answer to that question, it depends on too many factors. Like I said earlier in this thread: "... the discussion is pretty much at "merry-go-round" status."

http://giphy.com/gifs/friend-carousel-70QvaOrAVmWsM

Fact is, we've both found examples where the added increase in oil temperature due to increased load/combustion heat is all over the place. Some are relatively insignificant deltas, others are more significant deltas - ranging anywhere from 8 to 30 deg C. As said before, the added increase in sump temperature due to load is dependent on many factors, and that's why the numbers vary so much. You can't pull one example out of your behind and say it fits to every situation. Yes, we all agree that the internal friction in the engine contributes more heat into the oil than combustion does ... that was never a point of contention to begin with. It's always been said they both contribute to heating the oil. So what's the point with these merry-go-round rides?

The testing done in Figure 2 above is however a good example of an extreme case when there is no added oil cooler and the cooling system is most likely marginal to begin with (those "high tech" cars of the early 70s). The oil sump temperature is highly dependent on the cooling system effectiveness. Design an engine with a highly efficient cooling system within the engine itself along with a gigantic radiator with tons of airflow, and also add an oil cooler, and that combination will make the added heat from combustion pretty insignificant. Take away cooling system efficiency and any added oil coolers, and sump temperature will increase according under extreme engine loads - just as some of these examples have shown. It's really not rocket science.

 

[Shannow]

"could be"...when you could have actually found out for yourself ???

So you chase me around, stick it to me over your strawman "perception" of "my position" for WHAT purpose ???

 

[ZeeOSix]

You need to realize you are the one who creates the perception of yourself to the world. Just like in the journal bearing discussions, you were so adamant that pressure fed bearings didn't flow any additional oil that you had to go dig up the stuff yourself and prove it to yourself. Then after all that, you reverted back to claiming they only flow what the side leakage is due to just their rotational speed.

If you don't want me to participate in these threads, then don't post them. Can't you stand someone who challenges some of what you post, or do you just want people to go 'oooh, aaah' when you post this stuff up. You want everyone to agree with you, but it's evident that you're not always right ... nobody is. Frankly, you posted up this thread so you could continue this discussion from the Vette thread. Well, it's was discussed again with basically the same end result it had in the Vette thread. Hey, we both like a good argument/debate, but it's time to get off the merry-go-round on this one.

 

[Shannow]

Originally Posted By: ZeeOSix
Y Just like in the journal bearing discussions, you were so adamant that pressure fed bearings didn't flow any additional oil that you had to go dig up the stuff yourself and prove it to yourself. Then after all that, you reverted back to claiming they only flow what the side leakage is due to just their rotational speed.




strawman again...

 

[ZeeOSix]

Want to go back to the journal bearing discussions for another round?

https://bobistheoilguy.com/forums/ubbthreads.php/topics/4248212