Valvetrain wear...what Rat DOESN'T do...

[Garak]

Originally Posted By: Shannow
The sum of differences then points to only a single factor remaining...losses due to increased engine (and transmission) speed.

That part I get, but I'm still wondering how one would calculate the work in this case. Am I correct in that one can look at it from different frames of reference and different coordinate systems? The work done on the car as an object being moved over a displacement is clear, but the reason I am waffling around the engine is because there is extra friction, and more piston miles, as it were, so more work.

And as you've mentioned, the friction is significantly higher at 4,000 rpm than at 1,800 rpm. Of course, if it wasn't higher, it wouldn't use more fuel in the first place, at least once you got it going.

 

[turtlevette]

Originally Posted By: Garak
Originally Posted By: Shannow
The sum of differences then points to only a single factor remaining...losses due to increased engine (and transmission) speed.

That part I get, but I'm still wondering how one would calculate the work in this case.


You're getting sidetracked on the work. I can build a fire in a pit. It creates heat. Does it do any work? A kid pushes a grocery cart. A huge bodybuilder pushes the same cart. The work is the same. The man expends more energy.

 

[BrocLuno]

Sorry, have I missed something here... This started out as a RAT's test does not ... Where is this data directly related to high valve spring loads on highly modified traditional layout V-8 with flat tappet cams and lifters? That was and is the basis for Rat's testing and analysis... He's trying to solve lifter and cam failure in USA style V-8 race motors ...

I like you'all a bunch and I learn stuff here. But I may just be to slow to make the link here ...

 

[Shannow]

OK, some points from the quotes I put up.
* contact pressure changes with dynamics at RPM...Rat's is a traditional grease wear test arrangement, just keep forcing until the lube fails.
* SAE paper found viscosity creating differences, RAT's testing does not, in fact he is totally dismissive of viscosity.
* SAE found behaviour of lubricants changes drastically in an environment of blowby gasses. Rat's testing doesn't have it.
* SAE found a marked difference between a plain "turning" test and an actual running engine, Rats doesn't.

If his techniques fail to discriminate between behaviours that occur in actual running engines, then his conclusions are at least sketchy.

 

[BrocLuno]

Agreed. Thanks for the clarification

But, what I do think is maybe appropriate for Rat's tests are track engines that get fresh oil very often, if not each race outing. And are cold started a lot and still loose cams and lifters.

In that scenario, his warm-oil pressure test is somewhat informative ...

Even though he extrapolates a LOT (

), his problem statement is/are track engines. I think his testing is more appropriate to trailer queen drag motors than anything else ... They have long cool-down periods between rounds and go from cold start to 8,000 RPM and full power in minutes.

True hot running viscosity is not really the forte of drag cars. It is for roundy-round cars

 

[Garak]

Originally Posted By: turtlevette
You're getting sidetracked on the work. I can build a fire in a pit. It creates heat. Does it do any work? A kid pushes a grocery cart. A huge bodybuilder pushes the same cart. The work is the same. The man expends more energy.

I'm intentionally going on a tangent on the calculation part of it, but don't discount the importance of work in this. Work and energy use the same units, and you should be well aware of why, as an engineer.

The fire in the pit is doing work. It's pushing gases around, including the air, and these gases have mass. Moving a mass takes force, and the movement is a displacement. Hence, there is work being done. Moving the grocery cart takes the same amount of work despite who does it. The body builder only expends more energy if he's doing more work because he's moving his bulky body with it, while the kid doing the same thing has a lot less mass. The person pushing is part of the system, or not. And, either way, you have to account for all energy expended. There is useful work, there is work, and there is waste, which is what I'm getting at in the first place.

A certain mass of fuel has a certain number of joules that can be released upon burning. Some of that becomes, yes, waste heat. Some of that does useful work in moving the vehicle forward. Some is overcoming friction in various parts of the vehicle, including the engine, also creating heat.

And, sumps get hot without there being an internal combustion engine, either.

 

[BrocLuno]

Originally Posted By: Garak


And, sumps get hot without there being an internal combustion engine, either.


They sure do. If you've ever run an electrically driven hydraulic system, it's amazing how hot all the tanks get after some operating time ...

 

[turtlevette]

Originally Posted By: Garak
Originally Posted By: turtlevette
You're getting sidetracked on the work. I can build a fire in a pit. It creates heat. Does it do any work? A kid pushes a grocery cart. A huge bodybuilder pushes the same cart. The work is the same. The man expends more energy.

I'm intentionally going on a tangent on the calculation part of it, but don't discount the importance of work in this. Work and energy use the same units, and you should be well aware of why, as an engineer.

The fire in the pit is doing work. It's pushing gases around, including the air, and these gases have mass. Moving a mass takes force, and the movement is a displacement. Hence, there is work being done. Moving the grocery cart takes the same amount of work despite who does it. The body builder only expends more energy if he's doing more work because he's moving his bulky body with it, while the kid doing the same thing has a lot less mass. The person pushing is part of the system, or not. And, either way, you have to account for all energy expended. There is useful work, there is work, and there is waste, which is what I'm getting at in the first place.

A certain mass of fuel has a certain number of joules that can be released upon burning. Some of that becomes, yes, waste heat. Some of that does useful work in moving the vehicle forward. Some is overcoming friction in various parts of the vehicle, including the engine, also creating heat.

And, sumps get hot without there being an internal combustion engine, either.


With arguments like that, the tiny respect I have for your technical knowledge errodes even more. I'm not going to counter as I do think you're at least smart enough to know how silly you get thinking you're going to win a debate. If we keep going back and forth, well have another EMP discussion going.

You remind me of cliff the mailman on cheers. A guy who is an expert in everything but does nothing.

 

[BrocLuno]

You guys are arguing about productive work vs work as generally defined. But what does that have to do with RATs tests and Shannows technical papers?

 

[Shannow]

BrocLuno,
turtlevette's snide...

Originally Posted By: turtlevette
Originally Posted By: userfriendly

The engine oil is also hotter and therefore thinner.

.


Naw, shannow will tell you its the shear that causes the real heat.


was the instigator in going off thread.

 

[Garak]

Originally Posted By: turtlevette
With arguments like that, the tiny respect I have for your technical knowledge errodes even more.

That's not an argument. That was being rigorous on the actual definition of work. Respect is irrelevant to the matter. I am either correct in defining work or I am not, and respect doesn't change whether I'm correct or whether I'm wrong. Respect or lack of it also has nothing to do with twisting examples about work so bad as to be unrecognizable to suit an unknown purpose. That garbage wouldn't fly in a grade 11 physics class.

And you still haven't attempted to pin down the sources of heat in an engine. Continuing on about fire doesn't do a lot to pin things down.

 

[userfriendly]

Will an Italian tune up work on a 900 rpm locomotive engine?
I know the answer, but I will throw out the question anyway.

Most modern locomotives have a high idle feature that increases the engine rpm during cold weather.

During extreme cold, the engines will "self load", which means the generator output could be as high as 3,000 hp.

The electric current is dissipated through the dynamic brake grid.

Failing that, the coolant is dumped onto the ground to prevent engine damage from freezing.

What heats the engine oil? My guess is the shear caused by rpm.

 

[CT8]

Tho oil in hydraulic systems heat up with use, where does the heat come from??? Friction from everything in the hydraulic system.

 

[Jeff_in_VABch]

Some of you guys just don't have any practical experience or knowledge about the basics of engine mechanics.

Who all has run an instrumented engine on an engine dyno?

 

[Garak]

Help us out here. We are sorely lacking in data.

 

[SteveSRT8]

Originally Posted By: Shannow
BrocLuno,
turtlevette's snide...

Originally Posted By: turtlevette
Originally Posted By: userfriendly

The engine oil is also hotter and therefore thinner.

.


Naw, shannow will tell you its the shear that causes the real heat.


was the instigator in going off thread.


I don't see how anyone, "engineer" or not, can ignore shear. Our industrial Blowers get to 300 degrees yet have zero combustion going on. Add to this they are pulling through a water/air mix which adds significant cooling.

I guess my tiny bit of respect (not) for TV's expertise (haw!) has eroded!

 

[Jeff_in_VABch]

Originally Posted By: SteveSRT8
Originally Posted By: Shannow
BrocLuno,
turtlevette's snide...

Originally Posted By: turtlevette
Originally Posted By: userfriendly

The engine oil is also hotter and therefore thinner.

.


Naw, shannow will tell you its the shear that causes the real heat.


was the instigator in going off thread.


I don't see how anyone, "engineer" or not, can ignore shear. Our industrial Blowers get to 300 degrees yet have zero combustion going on. Add to this they are pulling through a water/air mix which adds significant cooling.

I guess my tiny bit of respect (not) for TV's expertise (haw!) has eroded!


Are you talking about liquid ring pumps? Water sealed instead of oil sealed? Those as well as air compressors are an exercise in heat generation and cooling.

For auto engines, are you talking about shear as the mechanical stress in the plain bearings on the crank, rods and cam journals? That I believe does generate some heat. I would guess you could calculate an estimate pretty easily. But I don't think it is a high number. The major sources of friction in an engine are piston skirts and piston rings.

When you dyno test an engine, you have to warm it up thoroughly before making any pulls. I would not do a pull under 180F oil temp. A cold run could cause a plain bearing failure, usually a rod bearing. Water, oil and EGT temperature is monitored and well as oil pressure and a few other things depending on the engine. The oil always wants to stay cool in an unloaded running condition and I found you have to load up the engine to really put some heat into the oil. As the engine load and cylinder pressure increases, the compression rings friction increases as well as the heat load. I never have just run an engine at high RPM (4 to 6K)with a light load on the dyno to try to warm it up (only rental cars when cold).

IMO a large portion of the oil temp is coming from the oil to head contact with the remainder heat coming from the block. At high RPM there is also heat being absorbed from the valve springs as the oil off the rocker cools the spring.

As the oil cascades downward onto the rotating assembly a tremendous amount of windage (5-30HP loss) is created, but this doesn't create heat other than the fact the engine is using additional energy internally.

Anyway, Im not so sure shear is a big contributor, but any fictional or energy loss is creating heat.

 

[Jeff_in_VABch]

Steve:

Do you know of any place to get a 5.7 Hemi crate motor that is a value?

I have a truck that needs a new long block.

Jeff

 

[Shannow]

Jeff,
this is from a Ricardo paper...

In the actual measured example (right, the left is motored), the FMEP is 1.5 bar. (not counting the auxilliaries, only the crank, cam and valvetrain, and reciprocating parts).

That totals 30KW (40hp) just in friction, which is predominantly oil shear...fr a 3L engine.

Given that the reciprocating group could be argues to have all of it's heat transferred to the cylinder walls, and it's about 2/3 of the total, that leaves 10KW just heating up the oil.

It's hardly insignificant.

The oil on the head surfaces (bar valves) and valley region should be limited to coolant temperature, as that's around the hotted that cooled unheated walls SHOULD get.

The oil draining off the crank and rods in my Caprice after 10 mins at 4,000RPM is 135, and that includes (obviously) valley drain back, so the big ends are hotter.

BTW, to answer your previous question, only a couple of times with instrumented engines on the dyno, Uni days, on test beds...we did power flows and heat balances but not contributors to oil temperature.

 

[CT8]

Originally Posted By: Trav
They are also very loud at high RPM, that why i said take a look at them again. New technology in hydraulics might offer some solutions that were not available years ago.
I have a feeling the electronic types of valve trains will be the future. Every time I look at the wife's 7.3 Powerstroke I have to wonder when will that asinine technology be used to open and close the valves. No cam lifters cam chain etc.