Engine Warm-Up Discussion.

[bobbydavro]

Originally Posted By: fredfactory
Originally Posted By: bobbydavro
Nice post. All makes sense and I have ran the IVA at lower temperatures and see lower numbers so it is defiantly on the sweet spot of wear.

Base oil is of little impact here, it's all about the chemistry. And driving rather than letting engine warm up at idle significantly reduces the camshaft loads.


Great inside info bobbydavro, thanks. Yet, are you talking about having the cam lobes moving across the followers at higher (than idle) engine speeds makes more hydrodynamic happen? I'm confused by your statement about camshaft loads.


Sorry that comment about driving was related to comments about people letting the engine warm up as they think its good to have a oil warm before doing work. However its working much harder at idle as the camshaft nose loads (thus the pressure in the cam/tappet interface) is higher due to the dynamics of low camshaft speeds. As speeds in crease this load reduces.

'66% higher camshaft loads in trffic than normal driving'

 

[Jetronic]

I wonder how much cam rollers vs flat tappets influence the nose loading. I'd imagine the peak loads are lower for roller followers

 

[fredfactory]

Originally Posted By: Jetronic
I wonder how much cam rollers vs flat tappets influence the nose loading. I'd imagine the peak loads are lower for roller followers


On roller followers, seems the loads are transferred to the pin bearings inside.
Kendall mentioned a lot of wear on the roller pins.

Its from the often-idling engines in NYC taxis in the Kendall test:

 

[CT8]

Originally Posted By: fredfactory
Originally Posted By: CT8
Oil drains from all the bearing journals and passage ways above the filter. That is why there are rattles when you start the engine . there is air in the oil passages.


From the oil filter upward to the crank, the oil should stay in those passages because of the ADBV in the oil filter. I understand how a lot of oil will leak out the clearances in the rod and main bearing surface parts, yet the passages leading to it should be full of oil.

Refer to the diagram below, although that engine has the oil filter above the crank, might be engine design differences that would influence whether or not you have a "pre-charge" of oil (less air).

This is important on startup of course for all the Stribeck physics to work, the oil has to be there. Some thick oil is there anyway, as not ALL drains out of the crank and main bearings.
The oil has no seal to keep the passage ways full. The anti drain back is to keep the oil from back washing the debris from the filter to the oil pump /sump.

 

[fredfactory]

Originally Posted By: CT8
The oil has no seal to keep the passage ways full. The anti drain back is to keep the oil from back washing the debris from the filter to the oil pump /sump.


Doesn't the ADBV valve in the oil filter stop up the gravity flow of oil from the main gallery (main is the gallery from the filter to the engine) back down to the filter? The filter's ADBV is a nitrile or silicon flap that plugs it up when the oil pump is not turning.

 

[CT8]

Originally Posted By: fredfactory
Originally Posted By: CT8
The oil has no seal to keep the passage ways full. The anti drain back is to keep the oil from back washing the debris from the filter to the oil pump /sump.


Doesn't the ADBV valve in the oil filter stop up the gravity flow of oil from the main gallery (main is the gallery from the filter to the engine) back down to the filter? The filter's ADBV is a nitrile or silicon flap that plugs it up when the oil pump is not turning.
No it keeps the oil from back washing the oil filter. There are no reals at any of the crank ,con rod bearings Cam bearings etc . The oil bleeds out of those areas when the engine is stopped. Have you ever taken an engine apart ?

 

[fredfactory]

CT8 ^^^^ Agreed, yes a lot of oil drains back out after shutdown, from bearings, etc. Main galley will have oil sitting in there. Its been years since I tore down engines. Engine design matters here of course, if the main gallery is upstream from the oil filter, oil stays in there.

 

[Ducked]

Originally Posted By: Shannow
Ducked...if you want to draw that conclusion, go your hardest...that's NOT my statement, recommendation, NOR interpretation of my work.


Hmm..OK, maybe a bit of wishful thinking colouring my interpretation there, BUT it does seem to follow.

Given that you seem to be saying that (a) high viscosity promotes hydrodynamic lubrication of the valve train, and (b) you seem to agree that high viscosity will promote early activation of the anti-wear additives, the argument against that interpretation seems to rest on lack of oil on startup, due to pumping resistance, and you seem to deprecate that.

Its quite likely I'm missing or adding something, though.

What is it?

 

[OVERKILL]

Originally Posted By: Ducked
Originally Posted By: Shannow
Ducked...if you want to draw that conclusion, go your hardest...that's NOT my statement, recommendation, NOR interpretation of my work.


Hmm..OK, maybe a bit of wishful thinking colouring my interpretation there, BUT it does seem to follow.

Given that you seem to be saying that (a) high viscosity promotes hydrodynamic lubrication of the valve train, and (b) you seem to agree that high viscosity will promote early activation of the anti-wear additives, the argument against that interpretation seems to rest on lack of oil on startup, due to pumping resistance, and you seem to deprecate that.

Its quite likely I'm missing or adding something, though.

What is it?


Either oil pumps, or it doesn't. That's the point of the MRV test.

 

[Ducked]

Originally Posted By: OVERKILL
Originally Posted By: Ducked
Originally Posted By: Shannow
Ducked...if you want to draw that conclusion, go your hardest...that's NOT my statement, recommendation, NOR interpretation of my work.


Hmm..OK, maybe a bit of wishful thinking colouring my interpretation there, BUT it does seem to follow.

Given that you seem to be saying that (a) high viscosity promotes hydrodynamic lubrication of the valve train, and (b) you seem to agree that high viscosity will promote early activation of the anti-wear additives, the argument against that interpretation seems to rest on lack of oil on startup, due to pumping resistance, and you seem to deprecate that.

Its quite likely I'm missing or adding something, though.

What is it?


Either oil pumps, or it doesn't. That's the point of the MRV test.


Too cryptic for me, mate.

"Either oil pumps, or it doesn't."

So it is an issue, or it isn't.

Well, yeh.

Plus I've actually had a magnetic resonance venography, and that wasn't the point.

 

[Shannow]

What OVERKILL is saying is that provided the oil isn't started at temperatures that it won't pump at, it will pump and move through the engine.

The empty galleries will fill, and oil will issue at around the same time, as I said for appropriate "W" rating for the temperature...Taiwan or Australia, we'll never get to explore the limits of 15W, and probably not 20W.

Otherwise, I've never pulled apart a dry engine...bearings and pistons you always get considerable oil on you from the stuff that's held there via capillary action...there's even a (much smaller) amount on cams and followers...it's naturally cold and quite thick compared to running viscosity.

as to b), no I don't believe that the internal friction of the heavier oils materially activates additives.

 

[Ducked]

Originally Posted By: Shannow
What OVERKILL is saying is that provided the oil isn't started at temperatures that it won't pump at, it will pump and move through the engine.

The empty galleries will fill, and oil will issue at around the same time, as I said for appropriate "W" rating for the temperature...Taiwan or Australia, we'll never get to explore the limits of 15W, and probably not 20W.

Otherwise, I've never pulled apart a dry engine...bearings and pistons you always get considerable oil on you from the stuff that's held there via capillary action...there's even a (much smaller) amount on cams and followers...it's naturally cold and quite thick compared to running viscosity.

as to b), no I don't believe that the internal friction of the heavier oils materially activates additives.


Your last point doesn't seem consistent with your above statement that "The 25W50 was for demonstration purposes...you are right, it would heat quickly due to shear in the bearings"...if it heats quickly, and the additives are heat activated, then they are activated sooner, surely?

Otherwise, as I said, you seem to again be deprecating the "thin is better, cos it gets there quicker" position, which I like, because it matches my own bias.

Maybe straight 40W is pushing it too far (I normally use Delvac 15/40) and I'll probably change it out for the "not-summer". Might try cranking with the rocker cover off to see what actually happens.

 

[Ducked]

I found a bit on it in "Relationship Between Engine Oil Viscosity and Engine Performance, Parts 5 " on Google books. Apparently MRV also stands for Mini Rotary Viscometer, a gizmo used to predict pumpability failure point (BPT = Borderline Pumping Temperature).

BPT in an engine test is apparently defined as a gallery pressure at or below 138kPa after one minute of pumping. This cutoff was selected on the (rather subjective?) basis of engine noise.

Pumpability failure has two main modes. "Air binding" where the oil gels and channels, so the pump is sucking air, and limiting viscosity, where the oil wont pass the screen.

BPT's (for 16 reference oils involved in the initial MRV validation tests) were generally around -30C, with the highest (oil number 5) at -18C.

I don't know what the reference oils were, but since I'll probably never experience temperatures below 0C here, IF it was true that oil "either pumps or it doesn't", (implying no adverse pumpability effects above the BPT, which the paper didn't confirm) then I probably wouldn't have to worry about it.

 

[ReverendC]

I recall a service bulletin in a Ford dealership many years ago. The camshafts on Pinto engines were breaking in two from lack of startup lubrication. The only Pintos that were not frying their camshafts were those owned by people who were faithful "warm up" owners. Ford then got very interested in 5-30 oil and told owners to get lighter viscosity oil regardless of climate. The bulletin said in short, "get some oil there and get it there quick." Now they want 5-20 in everything. When I start my seldom used 1990 Chevy truck, I hate that 3 seconds of engine rattle knowing that lots of metal things aren't getting any oil. Engine number four can't be far off.

 

[OVERKILL]

Originally Posted By: Ducked


Too cryptic for me, mate.

"Either oil pumps, or it doesn't."

So it is an issue, or it isn't.

Well, yeh.

Plus I've actually had a magnetic resonance venography, and that wasn't the point.


Mini Rotary Viscometer, not Magnetic Resonance Venography, LOL! Nice medical tie-in though

Seriously though, that's the reason for the MRV limits set "as they are" (though some may disagree with the points they are set at). If you are using an oil within the range it is approved for, it will pump.

 

[OVERKILL]

Originally Posted By: Ducked
I found a bit on it in "Relationship Between Engine Oil Viscosity and Engine Performance, Parts 5 " on Google books. Apparently MRV also stands for Mini Rotary Viscometer, a gizmo used to predict pumpability failure point (BPT = Borderline Pumping Temperature).


And here I thought you were making a funny

Yes, two things often discussed on here are MRV and CCS (the latter being Cold Cranking Simulator). They are the metrics used to establish whether an oil is a 0w-xx, 5w-xx, 10w-xx....etc.

 

[CT8]

Originally Posted By: fredfactory
CT8 ^^^^ Agreed, yes a lot of oil drains back out after shutdown, from bearings, etc. Main galley will have oil sitting in there. Its been years since I tore down engines. Engine design matters here of course, if the main gallery is upstream from the oil filter, oil stays in there.
no.

 

[datech]

Originally Posted By: ReverendC
I recall a service bulletin in a Ford dealership many years ago. The camshafts on Pinto engines were breaking in two from lack of startup lubrication. The only Pintos that were not frying their camshafts were those owned by people who were faithful "warm up" owners. Ford then got very interested in 5-30 oil and told owners to get lighter viscosity oil regardless of climate. The bulletin said in short, "get some oil there and get it there quick." Now they want 5-20 in everything. When I start my seldom used 1990 Chevy truck, I hate that 3 seconds of engine rattle knowing that lots of metal things aren't getting any oil. Engine number four can't be far off.



I remember reading a long time ago a magazine article that examined how long an engine could sit before bad things started happening. I think it said they started to find rust forming in the cylinder after 10 days.

What is your experience in how long an engine can sit before it has noticeable noise?

 

[Ducked]

Originally Posted By: OVERKILL
Originally Posted By: Ducked
I found a bit on it in "Relationship Between Engine Oil Viscosity and Engine Performance, Parts 5 " on Google books. Apparently MRV also stands for Mini Rotary Viscometer, a gizmo used to predict pumpability failure point (BPT = Borderline Pumping Temperature).


And here I thought you were making a funny

Nothing funny about magnetic resonance venographs. They don't hurt, but they don't tickle either.

I suppose I was making the point, in passing, that not everyone reading these threads knows ALL the undefined acronyms that get chucked around. I did a site search on MRV on its own and got bugger-all. If you Google it you get what I got/had, i.e. magnetic resonance venograph.

Still, I suppose it keeps most of the tourists away. Would have worked on me but the alternative was doing some work.

 

[Ducked]

Originally Posted By: ReverendC
When I start my seldom used 1990 Chevy truck, I hate that 3 seconds of engine rattle knowing that lots of metal things aren't getting any oil.


If the paper I found is still current, the BPT (Borderline Pumping Temperature) is defined after a minute of cranking. Listening to that for a full minute would hurt.

I'd like to believe that this is a binary go/no go phenomenon, (oil pumps or it doesn't) and maybe it is, but its a bit of a stretch. The fact that it seems to be defined as a cutoff isn't very persuasive on its own, since that might just be for procedural convenience.