2013 BRZ - Two UOAs (GC0w30 and Toyota SN 0w20)

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Originally Posted By: nickolas84
Let me explain my ignorance then.

Well done. Much appreciated.

Originally Posted By: nickolas84
If you have to add an oil cooler you better make it one with a thermostat. Otherwise when cruising you will never reach normal oil temperature which can really hurt your engine.

Using a non-controlled heat-exchanger is never (ever?) recommended, why would you even think that that's a normal thing to do?
 
@OVERKILL With a cold engine you reach max oil pressure right of idle. Which is to say the relief valve opens right of idle. If you redline a cold engine pretty much all of the oil goes through the relief valve.
The bearings are not hydrodynamically lubricated especially at low rpm.
Now let me find that SAE paper...
So far the discussion was about kinematic viscosity. HTHS is different and yes is important.
 
Originally Posted By: nickolas84
@OVERKILL With a cold engine you reach max oil pressure right of idle. Which is to say the relief valve opens right of idle. If you redline a cold engine pretty much all of the oil goes through the relief valve.


Depends on the engine, depends on the oil pump, depends on what you define as cold as to how much of the oil if any ends up going out the relief. That said the relief is in and of itself an orifice with a maximum size and is there to regulate the pressure in the system. So no, "pretty much all the oil" does NOT go out the relief, only the volume that the engine is unable to flow at a given head pressure. Again, I welcome you to fire up a cold engine with the valve covers off and tell me where all that oil is coming from when it is supposedly going out the relief on the pump.

Is it easier to hit the relief pressure with cold oil? Of course. The pump is going to move the same volume of oil whether the oil is super thin or crazy thick. And the feed for the engine is only so big, so there's only so much of that oil it is going to be able to stuff down that passage at a given pressure. That pressure is of course dictated by the relief. Now what you will often see with HV pumps on an engine like an SBF or SBC with stock bearing clearances that somebody has put 20w-50 in and doesn't wait for the oil to come up to temp is oil pressure well above the rating on the relief. "Why?" you say? Because as I stated, the relief valve has an orifice of a maximum fixed size and the pump is going to move the same volume of oil regardless. So the pump will build pressure above and beyond the limit of the relief in the system with pressurized oil going both into the engine AND out the relief.

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The bearings are not hydrodynamically lubricated especially at low rpm.


I'll let Shannow deal with that part, as he designs bearings for a living so I'm sure you'll respect his input here more than mine.

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Now let me find that SAE paper...


Please do. Though without saying what it is about that reference is pretty vague....

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So far the discussion was about kinematic viscosity. HTHS is different and yes is important.


Yes, but kinematic, like HTHS, is temperature dependant. That's the thing about viscosity.
 
Originally Posted By: nickolas84
The bearings are not hydrodynamically lubricated especially at low rpm.
Now let me find that SAE paper...


Your choices are:
* hydrodynamic;
* hydrostatic;
* boundary;
* mixed.
 
Yeap. Though I would consider hydrostatic of minimal importance which leaves hydrodrodynamic, boundary and mixed.
There seems to be no hydrodynamic lubrication at bearings in low rpm/high load situations, which tends to be the norm with fuel economy driving.
In these situations no matter how viscous the oil, boundary lubrication is the norm, thus the additive package and not viscocity is the determing factor for engine longevity.
There was a SAE paper that stated this even for XXW-60 oils but I cannot find it.
All I can find is this that only refers to low friction oils.
http://papers.sae.org/981408/
 
@OVERKILL the volume flow rate is inversely proportional to viscosity. So if say your oil cold is 5 or 10 times more viscus than fully warmed, oil flow to the engine will be 5 or 10 times less as well. Adding the fact that most engines reach max oil pressure at middle rpm and not redline, things get twice as worse at redline. It is true that oil pressure is out of control at cold starts. It is a bad thing for your oil pump first of all and the reason is the oil is too viscus to even go through the relief valve.
 
This probably needs another thread all of it's own to explain this new physics...how is flow inversely proportional to viscosity in a positive displacement pump ?

Pressure is only there to supply oil, the bearings draw that which they need from the elevated supply pressure.

And in the vast majority of engine operation where hydrodynamics reigns, thicker oil needs less replenishment volume...which is what drives the high pressure...the engine needs less flow, and is resistant to it.
 
Originally Posted By: nickolas84
@OVERKILL the volume flow rate is inversely proportional to viscosity.


Shannow covered this so I'm going to leave it alone.

However:

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So if say your oil cold is 5 or 10 times more viscus than fully warmed, oil flow to the engine will be 5 or 10 times less as well. Adding the fact that most engines reach max oil pressure at middle rpm and not redline, things get twice as worse at redline. It is true that oil pressure is out of control at cold starts. It is a bad thing for your oil pump first of all and the reason is the oil is too viscus to even go through the relief valve.


I think we need some perspective. You sound like you are talking about an engine starting with 20w-50 in it in the middle of winter in Calgary.

Oil "flow" doesn't change with the viscosity as long as the relief on the pump is closed. Once the relief opens, yes, volume observed through the engine is reduced. But high pressure does not indicate reduced flow unless the relief is open. So no, unless you have the relief OPEN, oil flow to the engine isn't reduced by 5, 10 or whatever number you decide to toss out here.

If I fire up my 302 on a typical spring day with 0w-40 in it, it isn't on the relief at idle, at high idle, or even 3,000RPM. The relief is 65psi. I can hit the relief pressure if I romp on it, but that would be moronic. Ergo, with that relief closed, the engine is seeing the same volume of oil if the oil was fully hot or 20C.

Now in the WINTER, on a cold start, I could see 45-50psi when it was -20C out on the high idle after start. Still not on the relief (so ALL that oil is going through the engine). If I were to be an idiot and give it some RPM, yes, I could force the relief open and start bypassing some of that oil back into the pan but I think we can both agree that this wouldn't be a bright move on a cold engine.
 
Originally Posted By: Shannow
This probably needs another thread all of it's own to explain this new physics...how is flow inversely proportional to viscosity in a positive displacement pump ?

Pressure is only there to supply oil, the bearings draw that which they need from the elevated supply pressure.

I think you're going to have to repeat this on the hour here everyday until everyone gets it.
 
I was referring to flow to the engine given the pressure relief valve. Unfortunately I don't have oil pressure reading in my engine, but a friends NC MX5 hits the relief at ~3500rpm when warm, and that is the norm as far as I know. Around here 5W-XX is what Mazda specs for the MX-5; 0W might be quite different.
BITOG recently published "Motor Oil University". You can check it here MOTOR OIL UNIVERSITY. It goes through all of this and the benefits of modern "synthetic" thin oils in great detail.
 
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Originally Posted By: nickolas84
BITOG recently published "Motor Oil University". You can check it here MOTOR OIL UNIVERSITY. It goes through all of this and the benefits of modern "synthetic" thin oils in great detail.

It isn't recent at all, and isn't a replacement for a course in fluid dynamics. In any event, oil pump pressure relief operation has been discussed at length in the PCMO section recently. But, if you can educate Shannow on bearing lubrication, by all means, proceed.
whistle.gif
 
Originally Posted By: nickolas84
Unfortunately I don't have oil pressure reading in my engine, but a friends NC MX5 hits the relief at ~3500rpm when warm, and that is the norm as far as I know.

We also need to remember that different engines can have very different minimum pressure specifications, and without that data (and preferably some actual pressure readings), a lot of this is just guessing. The rule of thumb often quoted for oil pressure is 10 psi per 1000 rpm. My G, however, actually calls for in excess of 20 psi per 1000 rpm, with oil at 80 C.
 
Originally Posted By: nickolas84
BITOG recently published "Motor Oil University". You can check it here MOTOR OIL UNIVERSITY. It goes through all of this and the benefits of modern "synthetic" thin oils in great detail.

This is one more case of someone thinking that what they read on the internet is true. Those articles seem to fill some people with more falsehoods than they had before they read it. At the same time, their estimate of their knowledge on the subject increases, and then they become not only more "wrong", but more confident that they are not wrong. One forum member wrote those articles. BITOG should not have posted them, in my opinion.
 
Originally Posted By: nickolas84
I was referring to flow to the engine given the pressure relief valve. Unfortunately I don't have oil pressure reading in my engine,


Let me cut you off right there. So you have ZERO practical first-hand experience with this subject and you are lecturing those of us that DO on "how things work"?

Why do you think I told you to pull a valve cover on a cold engine and fire it up to observe oil flow? Because that's the easiest way for you to verify that whatever you are theorizing here is patently false. I've done this. On an SBC, SBF, an old 440 Mopar, even some antique boat engines. I've had the valve cover off a Modular when it was fired up too. They ALL had one thing in common: A whole heck of a lot of oil going all over the place within a couple seconds of the engine firing up. About the only one I can recall going onto the relief was an SBC with an HV pump with 20w-50 in it which would hit 60psi, which was the relief on the pump. Give it some gas and it would go above the relief pressure. It was like Niagra falls in the heads; there was a LOT of oil moving.

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but a friends NC MX5 hits the relief at ~3500rpm when warm, and that is the norm as far as I know.


The norm for that engine perhaps. What grade of oil is in the pan?

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Around here 5W-XX is what Mazda specs for the MX-5; 0W might be quite different.


5w- what? 5w-20, 5w-50? That's a rather hugely vague area for you to leave open. And no, 0w-xx won't be any different, as the difference between a 3.1cP HTHS 0w-30 and 5w-30 is their performance at -30C and -35C and -35 and -40C respectively (CCS and MRV). Step out of the extreme cold temp range and the behaviour between the oils is basically a wash. The advantage of a 0w-40 over a 5w-40 is its cold temperature performance, not its performance on a 30C start.

It sounds like you don't quite have your head wrapped around viscosity either.

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BITOG recently published "Motor Oil University". You can check it here MOTOR OIL UNIVERSITY. It goes through all of this and the benefits of modern "synthetic" thin oils in great detail.


As others have stated, that's not recent. It is a relatively old series of articles written by a resident poster, who is a plastic surgeon by trade. A very intelligent man but as JAG has noted, these dissertations that he's authored have resulted in many people thinking they know a lot more than they actually do. And getting many of the fundamental concepts completely wrong.
 
JAG for most people, me included, this is professional information and not an opinion article. If someone knows better he should address that.
I didn't know it was a text on BITOG forum, but I have read it as a post on a Ferrari forum.

This is really big (and really off topic). Is fuel economy and wear protection with regard to engine oil opposites or can they come together? It seems with modern additive packages and smaller engine clearances, plus the increased hp/rpm/cc and fuel economy driving, things move away from hydrodynamic lubrication and what it dictates making viscosity no longer important and HTHS not that important. The BMW M motor case I thing is a shining example.

@Garak that is the reason I am referring to rpm the relief valve opens with warmed up oil and not pressure numbers.

EDIT: Overkill the MX5 oil is 5W-30. Based on your experience what rpm range is the norm for a relief valve to open? I do not have much hands on experience but I know basic physics and math. They can do the job too.
 
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Originally Posted By: nickolas84
plus the increased hp/rpm/cc and fuel economy driving, things move away from hydrodynamic lubrication and what it dictates making viscosity no longer important and HTHS not that important. The BMW M motor case I thing is a shining example.

@Garak that is the reason I am referring to rpm the relief valve opens with warmed up oil and not pressure numbers.



Not sure where this is coming from
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If you are referencing BMW using their (heavy) 5w-30 in the newer M motors, that isn't new. The S62 spec'd the LL-01 5w-30 as well (which is what is in my M5). BMW also leverages a thermostatically controlled oil cooler as well as a large sump to dictate and control operational viscosity of the lubricant. Viscosity is more than just a number on a bottle. Operating viscosity is a design parameter and CONTROLLING operating viscosity and then applying that to lubricant selection is key. The 10w-60 recommendation stemmed from BMW's motorsport use with that oil and with the 1st generation of S62, was recommended primarily to address oil consumption issues due to the low-tension rings. This was addressed in the post 03/00 engines, with no other internal changes, and the recommendation changed to the BMW LL-01 spec oils, which denote an HTHS of >=3.5cP.

BMW has simply gone BACK to that recommendation with their latest offering in the M-cars, and utilizing the same techniques they did in the past to control temperature and subsequently operating viscosity within the engine. There will be a thermostatic castration mechanism to protect the engine if oil temperature gets too high, which would cause the oil to be too thin to properly protect the engine.

Ford has a similar technique with the Mustang GT. The regular GT spec's 5w-20, whilst the "track pack" version of the same car, sporting the SAME ENGINE, but sold as "track ready" calls for 5w-50 and also has an oil cooler.

Ford utilizes a thermal castration mechanism cutting engine power if oil temperature gets too high. This allows them to spec 5w-20 for the one car and adequately protect it, whilst raising the ceiling on the other with the same engine and simply spec'ing a heavier oil.
 
Originally Posted By: nickolas84


EDIT: Overkill the MX5 oil is 5W-30. Based on your experience what rpm range is the norm for a relief valve to open? I do not have much hands on experience but I know basic physics and math. They can do the job too.


As I said in one of my earliest posts to you, it depends on the engine, oil pump, viscosity....etc. There are a variety of factors. For example the old 302 has your typical gear-style pump. The Modular runs a higher pressure higher volume gyrator style pump that is driven off the crank. There was a rather funny thing that happened to the odd Modular engine and that was the relief on the pump sticking, forcing ALL the oil through the engine at some insane oil pressure and causing the filters to explode!

Standard hot oil pressure on my 302 was ~32psi hot at idle. Relief, as I noted earlier, occurred around 65psi. I would hit the relief somewhere north of 5,000RPM, which is of course when the pump is moving a rather obscene volume of oil. This was with 5w-30 in it IIRC. It was a little lower in the RPM range with the 0w-40 in it.

Now keep in mind that just because the relief starts to open (it isn't a flood gate that just flies open, it is operated by a spring and will begin to crack at around the rated pressure to regulate the total pressure of the system) doesn't mean flow through the engine is reduced. On the contrary, what it means is simply that flow to the engine is being REGULATED. If my oil pump moves 5GPM of oil at 5,000RPM and at 5,000RPM I am at 60psi, that means that all 5GPM of oil is going through my engine. However, at 6,000RPM that pump may move 6GPM of oil but operating pressure is now being regulated to 65psi so the engine is not seeing all of that 6GPM, it is probably seeing somewhere around 5.25-5.5GPM due to the regulation being performed by the relief.

Mazda may have fitted the MX5 with a high volume pump that hits the relief early for whatever reason. Dodge seems to use a similar tactic.
 
The BMW story as I know it is different (click) and stemmed from bearing failures with the 10W-60 oil because of tight bearing clearencess.
The reduced oil flow to the engine when cold (please spare me the details of "cold" specification) is so basic it beats me! But here are some numbers (click). Based on this graph, the average 5W-30 oil is almost 30 times more viscus at 10C ("cold start") than 100C ("warmed up")
So if I have a positive displacement oil pump and hit the relief at 3500rpm warm, on a 10C cold start if I hit 3500rpm only ~4% of the oil pumped will go through the engine, compared to 100% when warm.
 
OK, you need to start your own thread on this new science that you have developed...you cannot equate the viscosity increase inversely proportional to reduced flow.

Your "logic" is entirely circular, in that you claim it, then defend your claim with your claim.

If it's so basically simple...prove it with science.

Then prove that flow = lubrication, which is obviously your assertion, using 101 to justify it.

You have claimed that bearings are lubed via boundary lubrication...which obviously does not need either flow, nor viscosity to get the job done.
 
Originally Posted By: Shannow
If it's so basically simple...prove it with science.

Then prove that flow = lubrication, which is obviously your assertion, using 101 to justify it.

You have claimed that bearings are lubed via boundary lubrication...which obviously does not need either flow, nor viscosity to get the job done.

Hagen–Poiseuille equation
d7fc954111a08e3140b5005f6014bd32.png


You can consider DP to be equal to P assuming pressure is 0 when oil drops to the oil pan. So pressure is analogous to both μ (dynamic viscosity) and Q (volumetric flow rate). For a given pressure, if μ increases 30 times Q will have to decrease 30 times. I know this assumes laminar flow etc. but the principle that with the oil cold, oil flow to the engine is severely reduced still holds.

The rest is on BITOG's "Motor Oil University". You need to address that if you disagree.
Unfortunately I cannot find the paper stating the boundary lubrication on bearings under high load even with 10W-60 oil but I am sure I read it on a legitimate source. You have me on that one.

EDIT: It seems bitog forum cannot accept Greek! Explanation of symbols is here (wiki)
 
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