Engine wear not linear with engine speed?

[Hokiefyd]

This graph (among a few others) was posted in the thread about Chrysler revising the oil grade recommendation in 2013 Pentastar engines. But what was most interesting to me is, unless I'm reading the graphs wrong, wear does not appear to be linear with engine speed. The graphs above describe cam face wear, but others depicting bearing wear seemed to reveal a similar pattern.

The way I read the 90*C graph for instance, and I may be reading it wrong, is that the cam face experiences the most wear at slower engine speeds, and the least wear at higher engine speeds. But looking at the 2.4 HTHSV numbers, it's not really linear. The highest wear was at 4000 rpm, then 5000 is lesser, then 3000 is lesser still, then 6000 rpm. I know no commonly available oil has an HTHSV of 2.4, but I'm still surprised by the data.

I would think this would be highly dependent on too many variables to list. Is this data really only relevant to the particular engine used in this particular test, or does this data represent a larger trend?

 

[heyu]

Originally Posted By: Hokiefyd

This graph (among a few others) was posted in the thread about Chrysler revising the oil grade recommendation in 2013 Pentastar engines. But what was most interesting to me is, unless I'm reading the graphs wrong, wear does not appear to be linear with engine speed. The graphs above describe cam face wear, but others depicting bearing wear seemed to reveal a similar pattern.

The way I read the 90*C graph for instance, and I may be reading it wrong, is that the cam face experiences the most wear at slower engine speeds, and the least wear at higher engine speeds. But looking at the 2.4 HTHSV numbers, it's not really linear. The highest wear was at 4000 rpm, then 5000 is lesser, then 3000 is lesser still, then 6000 rpm. I know no commonly available oil has an HTHSV of 2.4, but I'm still surprised by the data.

I would think this would be highly dependent on too many variables to list. Is this data really only relevant to the particular engine used in this particular test, or does this data represent a larger trend?



I see your point on this also

 

[Shannow]

The data is relevant to lubrication, as unlike what some on the board "feel", the laws of physics apply equally to all engine designs.

Those graphs demonstrate some of the simple rules of hydrodynamics.

The faster the speed between two rubbing surfaces, the greater the separation distance of the two parts. The greater the viscosity, the greater the separation.

Link here is really simplistic, but the basics truly are easy to understand.

lubrication stuff

 

[SteveSRT8]

Originally Posted By: Hokiefyd

This graph (among a few others) was posted in the thread about Chrysler revising the oil grade recommendation in 2013 Pentastar engines. But what was most interesting to me is, unless I'm reading the graphs wrong, wear does not appear to be linear with engine speed. The graphs above describe cam face wear, but others depicting bearing wear seemed to reveal a similar pattern.

The way I read the 90*C graph for instance, and I may be reading it wrong, is that the cam face experiences the most wear at slower engine speeds, and the least wear at higher engine speeds. But looking at the 2.4 HTHSV numbers, it's not really linear. The highest wear was at 4000 rpm, then 5000 is lesser, then 3000 is lesser still, then 6000 rpm. I know no commonly available oil has an HTHSV of 2.4, but I'm still surprised by the data.

I would think this would be highly dependent on too many variables to list. Is this data really only relevant to the particular engine used in this particular test, or does this data represent a larger trend?


I'm sure it does. But obviously the data is engine specific, as the cam lobes, power output, redline, and more vary wildly by engine design.

 

[NateDN10]

Not only is it not linear, it doesn't increase monotonically! (ie, 3000 rpm is higher than both 2000 and 4000)

 

[Shannow]

Originally Posted By: NateDN10
Not only is it not linear, it doesn't increase monotonically! (ie, 3000 rpm is higher than both 2000 and 4000)


Go to the link that I posted.

speed, viscosity and load...

 

[modularv8]

I noticed the same thing too when I read the study a while back, but it does make sense. In this study, Toyota used a 1.6L direct acting valve train engine. At lower engine rpm, the oil film strength is not sufficient enough to overcome the valve spring force on the lifter, therefore there is boundary friction. When the rpm goes above a certain threshold, the lubrication becomes hydrodyamic (think of hydroplaning)and the two components are separated by an oil film wedge, therefore less wear. At 3000 rpm, I think it is mixed boundary lubrication but may cause more wear than the other two regimes because it is in transition or oscillating between the two regimes causing more wear (bouncing on cam face). I have seen something similar with piston rings but not always. Anyway, unless you have flat-tappet or other direct acting type valve-train, it isn't important. Most modern engines have gone to roller-type lifters.

 

[vinu_neuro]

Like others have already said it's dangerous to draw broad conclusions this way. You are seeing a snapshot with two graphs (which aren't even wholly applicable to all) in this study out of six, plus a table of the oil compositions used. This is only cam wear, what about piston and bearing wear? What are the metallurgies, what are the rocker ratios, etc?

OEM's have millions of dollars, hours and miles behind their lubricant recommendations. Be wary when people on this board tell you to deviate significantly from them.

 

[440Magnum]

Before I even read ANY further down the thread, I'm going to flat-out state that I'll bet a juicy hamburger that the graphed data is from a sliding-follower(aka "flat" tappet) engine.

It looks pretty typical of such an engine, including the wear maximum (although 3000 RPM seems awfully high, I'd expect the peak around 1000-1500 RPM but then the data doesn't extend that low) a and then decrease with increasing RPM.

 

[modularv8]

Originally Posted By: vinu_neuro
Like others have already said it's dangerous to draw broad conclusions this way. You are seeing a snapshot with two graphs (which aren't even wholly applicable to all) in this study out of six, plus a table of the oil compositions used. This is only cam wear, what about piston and bearing wear? What are the metallurgies, what are the rocker ratios, etc?

OEM's have millions of dollars, hours and miles behind their lubricant recommendations. Be wary when people on this board tell you to deviate significantly from them.


Well said, vinu_neuro!

Ford alone spends $billions ($8 billion, 2007) each year on research and development. For the past 100 yrs of automotive and lubricant industry history, the OEM and scientific minds have thought about everything. A person buys all this R & D when they buy their vehicle. They only have to follow the OEMs owner's manual and enjoy their vehicle.

With that, I think I will quit BITOG now and focus my time on important stuff. Life is too short to be spend on motor oil.

 

[buster]

Originally Posted By: modularv8
Originally Posted By: vinu_neuro
Like others have already said it's dangerous to draw broad conclusions this way. You are seeing a snapshot with two graphs (which aren't even wholly applicable to all) in this study out of six, plus a table of the oil compositions used. This is only cam wear, what about piston and bearing wear? What are the metallurgies, what are the rocker ratios, etc?

OEM's have millions of dollars, hours and miles behind their lubricant recommendations. Be wary when people on this board tell you to deviate significantly from them.


Well said, vinu_neuro!

Ford alone spends $billions ($8 billion, 2007) each year on research and development. For the past 100 yrs of automotive and lubricant industry history, the OEM and scientific minds have thought about everything. A person buys all this R & D when they buy their vehicle. They only have to follow the OEMs owner's manual and enjoy their vehicle.

With that, I think I will quit BITOG now and focus my time on important stuff. Life is too short to be spend on motor oil.


+1

 

[Hokiefyd]

Originally Posted By: 440Magnum
It looks pretty typical of such an engine, including the wear maximum (although 3000 RPM seems awfully high, I'd expect the peak around 1000-1500 RPM but then the data doesn't extend that low) a and then decrease with increasing RPM.


That's what I would have expected as well. But the data seems to be all over the place. Just an observation I guess.

 

[FZ1]

Big Picture. 70-80% of wear is start up wear. Post start up,driving carefully,in the proper gear,is all we need to do.

 

[edhackett]

Originally Posted By: Hokiefyd

That's what I would have expected as well. But the data seems to be all over the place. Just an observation I guess.


Yes, I'd like to see some error bars on the data.

Ed

 

[Mitch Alsup]

Originally Posted By: Hokiefyd

I detect a bit of strangeness in the data.

The computer drawn line (90d; dashed) goes rather straight from 2.2 cSt to 2.6cSt WHILE the markers (triangle and box) flip. Since computers draw these lines (eXcel) perhaps an artist in the construction of the report, put the boxes at the wrong places. {It has happened to me more than once.}

Similar data anomolies are present in the 130d graph also.