Oil type and engine temps

[zeng]

Originally Posted By: Doug Hillary
A minimum HTHS viscosity factor will always be a controlling factor in lubricant design and this is especially so in the latest engines under development and especially so in regard emerging technologies (additives, metallurgy, coatings etc.)



+1

What about minimum oil diametral clearance of journal bearings ?

Does oil clearance still really matters when the industry may have hit the barrier at a minimum

clearance , in a friction vs oil clearance curve ?

 

[userfriendly]

Preventing the bearing clearance selected from changing during operation might be more important than a quest to minimize bearing clearances.
Controlling cylinder pressure (load), minimizing block flex and crank harmonics are a few off the top of my head.

One esteemed member (obviously not me,) said that picking an engine oil grade then designing the engine to suit it, is like the tail wagging the dog.

I don't imagine that means every well designed engine can magically operate on 0W16, or that 20W50 is a poorly designed engine requirement.

 

[Shannow]

Originally Posted By: zeng
Originally Posted By: Doug Hillary
A minimum HTHS viscosity factor will always be a controlling factor in lubricant design and this is especially so in the latest engines under development and especially so in regard emerging technologies (additives, metallurgy, coatings etc.)



+1

What about minimum oil diametral clearance of journal bearings ?

Does oil clearance still really matters when the industry may have hit the barrier at a minimum

clearance , in a friction vs oil clearance curve ?


Honda have stated in some of their papers that they are reducing the radial clearance, and lengthening the bearings, both of which create more friction, but allow a thinner oil.

I think they are chasing the piston/wall friction, which is very high mid stroke, and needing to further protect the bearings.

 

[zeng]

Originally Posted By: Shannow
Originally Posted By: zeng


What about minimum oil diametral clearance of journal bearings ?

Does oil clearance still really matters when the industry may have hit the barrier at a minimum

clearance , in a friction vs oil clearance curve ?


Honda have stated in some of their papers that they are reducing the radial clearance, and lengthening the bearings, both of which create more friction, but allow a thinner oil.

I think they are chasing the piston/wall friction, which is very high mid stroke, and needing to further protect the bearings.


Shannow, I was actually referring to a link provided by you sometimes back (which I had

difficulty in retracing it) , inside which a coefficient of friction vs journal oil diametral

clearance chart shows : at oil clearance approximately 0.001"(1 thousandth of an inch) and below

, friction coeff. becomes untenably high.

Unless new additives/materials/machining techniques etc chips in , otherwise we may have hit a

barrier in further lowering the oil clearance.

 

[userfriendly]

As power per liter goes up, Honda may have to add a little connecting rod length to reduce side load piston friction.

The turbo engines bring the power in sooner lowering the peak hp rpm keeping the shear rates in check with the tight bearing clearance, but what a balancing act.

Small bearing clearance, high rpm and thin engine oils, does fly in the face of someone else's work I read posted here recently.

 

[Jetronic]

Originally Posted By: zeng
From the figure provided ,in simple terms , am I ok to deduce that range of oil temperature rise

due to rpm increase is higher than that due to load increase ?

Interesting deliberations here ......................

yes, and from the last post by Shannow I get that you need to be very considerate of ambient temperatures, and the effect of high temps on oil cooling. That is, if you don't have an oil temperature gauge.

Given high enough bulk oil temperature, there's a very real possibility for boundary lubrication at high speed, high load resulting in bearing failure very quickly. Consider the influence of fuel dilution on HTHS and on the additive concentration here aswell, your oil might not be as strong as it was when new.

So if the oil temps start going up considerably, slow down the engine rpm by either shifting up a gear or slowing the vehicle down if already in top gear.

 

[Shannow]

Jetronic, nice summary, particularly with vis loss in service.

(You can also use the principal to speed up warmup )

 

[Jetronic]

And I do use the principal to speed up warmup, at times. When I need to get on the highway soon after starting for example.

I keep my automatic in Sports mode, which typically runs 2 gears lower than the normal and winter mode. I also get a boost pressure gauge and engine load graph then, so I can keep boost under 0.5 bar and load limited to 15% until the engine oil is hot (a few minutes after the engine coolant reaches it's normal temperature, there's an oil/coolant interchanger but no oil temp or pressure gauge). The fuel consumption at a given speed is also a good indicator of oil temp, but includes gear box oil temp aswell.

So now I'm after the thinnest KV40 and KV100 oil with an HTHS above 3.5, preferably low noack aswell. Mid-Sapa preferred but not a deal breaker. Price and availability are a consideration. Lowestr temp I've seen here ever has been -20C so the winter grade is of little importance.

 

[zeng]

Originally Posted By: Shannow
Jetronic, nice summary, particularly with vis loss in service.

(You can also use the principal to speed up warmup )


Before coolant reaches normal temperature , I had been religiously capping engine rpm to 2000-2500

rpm, thinking that valve train wear is being mitigated whilst awaiting higher oil temperature to

kick in activating AW additives ...... looks like I'm missing something here ?

 

[zeng]

-double post-

 

[zeng]

Originally Posted By: Jetronic
So now I'm after the thinnest KV40 and KV100 oil with an HTHS above 3.5, preferably low noack aswell. Mid-Sapa preferred but not a deal breaker. Price and availability are a consideration. Lowestr temp I've seen here ever has been -20C so the winter grade is of little importance.



I too had been chasing after HTHSv above 3.5 , thus confining to (Euro) xW40 oils only , not

realizing other thinner grades could present equivalent HTHSv.

 

[Jetronic]

Originally Posted By: zeng
Originally Posted By: Shannow
Jetronic, nice summary, particularly with vis loss in service.

(You can also use the principal to speed up warmup )


Before coolant reaches normal temperature , I had been religiously capping engine rpm to 2000-2500

rpm, thinking that valve train wear is being mitigated whilst awaiting higher oil temperature to

kick in activating AW additives ...... looks like I'm missing something here ?


The point is not to go to high loading of the engine until the engine oil is up tot emperature. above 80C is likely fine for most temperature activated additives to kick in.

Yes, keep revs limited when the engine is cold, but not if you have to go up something steep enough to approach the maximum torque the engine has to offer at low rpm. The pistons are not operating in the hydrodynamic lubrication regime for a fair bit of the stroke at low rpm, and this effect is worse with high torque. Also the valve train might be experiencing a lot of mixed or boundary lubrication at low speeds. The cam is running at half the RPM of the engine, and has a small circle resulting in slow speeds at the followers and bearings.

In your climate, I'd be looking at elf molygraphite or similar, if I expected to get high oil temps or lugging the engine. They are now API SN from what I've seen and available as a 10w30 which is likely to have aqn HTHSv of over 3.5

 

[Garak]

Originally Posted By: Doug Hillary
It was laughed out of the debates of the time by a few

Well, Doug, no one is left laughing any more.

Originally Posted By: Doug Hillary
The Euro OEMs were certainly leading the way with their Approvals systems way back when............MB had them in the 1950s!!

If you ever have the time to give us a history lesson on that one, I'm sure we'd all be very appreciative. Most of us have at least a passing familiarity with the more modern MB specifications, but know little about the background.

 

[Doug Hillary]

Hi,
Garak - MB published an Approved lubricants "Handbook" covering Brands and viscosities applicable for their vehicles - and applicable variously in all Countries where their vehicles were sold

I can't locate a copy now sadly but I do have a "Tabellenbuch Personenwagen" from July 1963. This handbook covers various service and maintenance requirements and was issued as required but typically annually IIRC

It applies to both petrol and diesel vehicles (including 300SL) and it's noted that OCIs were at 500km, 3000km and then 6000km thereafter

Filters were changed at every second OC, three filter types were used including a combined FF/By-pass

Many engine lubrication factors (OP etc.) were measured using an SAE10 lubricant at 90C

Sorry I couldn't locate the lubricants Handbook

Thre specific needs were met via HD lubricants as was VW & Porsche. We call these HDEOs today!

Then in Denmark I typically used HD lubricants with CAT & MiL "Approvals" whenever possible

 

[Garak]

Very interesting, Doug. Thanks for the information!

 

[SR5]

Originally Posted By: zeng
Originally Posted By: Jetronic
So now I'm after the thinnest KV40 and KV100 oil with an HTHS above 3.5, preferably low noack aswell. Mid-Sapa preferred but not a deal breaker. Price and availability are a consideration. Lowestr temp I've seen here ever has been -20C so the winter grade is of little importance.



I too had been chasing after HTHSv above 3.5 , thus confining to (Euro) xW40 oils only , not

realizing other thinner grades could present equivalent HTHSv.

Hi Zeng,

Have a read of this thread (if you haven't already)
http://www.bobistheoilguy.com/forums/ubb...ice#Post3772459

It's all about high HTHS xW30 and xW40 oils. My very rough reading of the thread is that the xW40 oils tend to have a higher starting HTHS so they don't shear out of grade after the KO30 test. The xW30 will shear less and have a lower starting HTHS.

We are talking Euro A3/B4 oils here, so for both starting HTHS is 3.5 or more.

 

[Pontual]

Originally Posted By: Shannow

- the actual bearing loads are not very different under the no load and full load conditions and part of the temperature increase may be attributed to the additional heat flow resulting from combustion (**)

[/quote]

I'd say most part of heat came from Oxigen combining with the combustible, under pressure and the presence of a ignition spark ...

 

[zeng]

Originally Posted By: Jetronic
Originally Posted By: zeng
Before coolant reaches normal temperature , I had been religiously capping engine rpm to 2000-2500 rpm, thinking that valve train wear is being mitigated whilst awaiting higher oil temperature to kick in activating AW additives ...... looks like I'm missing something here ?


The point is not to go to high loading of the engine until the engine oil is up tot emperature. above 80C is likely fine for most temperature activated additives to kick in.

Yes, keep revs limited when the engine is cold, but not if you have to go up something steep enough to approach the maximum torque the engine has to offer at low rpm. The pistons are not operating in the hydrodynamic lubrication regime for a fair bit of the stroke at low rpm, and this effect is worse with high torque. Also the valve train might be experiencing a lot of mixed or boundary lubrication at low speeds. The cam is running at half the RPM of the engine, and has a small circle resulting in slow speeds at the followers and bearings.

In your climate, I'd be looking at elf molygraphite or similar, if I expected to get high oil temps or lugging the engine. They are now API SN from what I've seen and available as a 10w30 which is likely to have aqn HTHSv of over 3.5


Meaning whilst awaiting coolant temperature to stabilize after cold start(at 26/7 C in my case) , without quick and sudden acceleration , it's beneficial to increase engine rpm beyond 2500 say,max at 3500/4000 rpm, to speed up oil temperature rise and increase linear speed of ring/liner and cam-lobe/tappet.

Thanks Jetronic , the key word is avoiding sudden acceleration whilst raising engine rpm from cold .

 

[zeng]

Originally Posted By: SR5
Originally Posted By: zeng
I too had been chasing after HTHSv above 3.5 , thus confining to (Euro) xW40 oils only , not realizing other thinner grades could present equivalent HTHSv.

Hi Zeng,

Have a read of this thread (if you haven't already)
http://www.bobistheoilguy.com/forums/ubb...ice#Post3772459

It's all about high HTHS xW30 and xW40 oils. My very rough reading of the thread is that the xW40 oils tend to have a higher starting HTHS so they don't shear out of grade after the KO30 test. The xW30 will shear less and have a lower starting HTHS.

We are talking Euro A3/B4 oils here, so for both starting HTHS is 3.5 or more.


Huuh , it was heavy reading the 9 pages.

Thanks a heaps , SR5.

 

[Shannow]

zeng,
some more data here
http://www.bobistheoilguy.com/forums/ubb...War#Post3853367