Will Thinner Oils Damage Your Engine?

[EMPIRE]

....... shows where the piston velocity is zero for a minuscule time period.

Intrument an engine with some higly sensitive and accurate sensors, super high speed slow motion video (did that at work on some stuff), whatever to measure distance and time ... or do it mathematically (kinematics) knowing the physical dimensions and motion of the components. As said before, the dt the piston is V=0 at TDC or BDC varies with engine RPM. Do it at 1 RPM and scale it from there.

Ok, but your graph post said

....... shows where the piston velocity is zero for a minuscule time period.

I am very interested in knowing the quantitative value of the small time period where v=0, for any rpm.
How small was the time period? Was it 2nsec, was it less than that, was it more than that? If the observation is say just 1nsec, then wow, that's some very very fast data acquisition sensors and software, it would need to be faster than 1GHz.

 

[4WD]

NO just stating facts between power plants there's a big change in design from a simple duratech to a Turbo TDI . PCMO demands are no the same . When it come verification on quotes if they are not backed by DATA l take them with a grain of salt . Take care

Factory OCI of 9000 miles with TDI and a semi syn oil per the factory engineers …
and what data did you bring ?

 

[EMPIRE]

dx/dt is undefined when both dx and dt = 0.



I'm not talking about "freeze framing" time like you're describing. I'm talking about if something is moving (like an engine running) when everything is moving with respect to time, which is constantly trudging alone like always. Time can theoretically be measured down to a Planck length = 5.39×10^-44 second. Even an engine at redline would have a dt at piston V=0 at TDC and BDC if you could measure it to a Planck length.

Do the math to find the dt at TDC or BDC when the engine is rotating super slow, like 1/10 RPM. There's a dt there when piston V=0, and there's a smaller and smaller dt at TDC/BDC as the engine RPM increases, but the dt never goes to zero when the piston V=0.

dx/dt does not mean divide.
On any timeline, anyplace on the timeline, when the differential in time shrinks to zero, you get a point on the timeline, some value of t. The 1st derivative gives us the observation as a "slice in time", "a point observation".

To know if motion has ceased (not moving, which has nothing to do with v=0), you must observe dx=0 (x1-x0=0 where x1=x0, the change in position, no change) for any time delta-t (dt, any change in time).

 

[ZeeOSix]

Well, the pistons do not stop. I already gave proof. The only way they stop MOVING is if dx=0 for any dt.

Show me any dt where dx=0 (with math), then you have proved me wrong.
until then, they do not stop moving.

https://x-engineer.org/automotive-e...systems/kinematic-analysis-of-the-ice-piston/

Look in the Exercise section:
"The piston’s speed goes through zero each time the piston is at TDC or BDC. This is because, at the dead centers, the piston changes direction, and for a fraction of the time it doesn’t move. This is the main reason for which internal combustion engines have flywheels on the crankshaft, to keep the pistons moving through the dead centers."

 

[ZeeOSix]

Whaaaaa? They are physically tied with a hunk of metal, how could their motions ever decouple? Sorry, no, that's 100% bad info.

And in actual terms, the crank drives the pistons, so it is the crank that affects the motion of the pistons. Study prime drivers of motion, then you'll understand this.

Never said they would "decouple".

Well, actually the pistons drive the crankshaft. Fuel + air goes boom in the combustion chamber, then the force on the dome of the piston pushes the piston down which transmits force through the rod to the crank arm - resulting in rotational torque on and motion of the crank.

The crank and rods however determine how the piston moves within the cylinder.

 

[4WD]

https://x-engineer.org/automotive-e...systems/kinematic-analysis-of-the-ice-piston/

Look in the Exercise section:
"The piston’s speed goes through zero each time the piston is at TDC or BDC. This is because, at the dead centers, the piston changes direction, and for a fraction of the time it doesn’t move. This is the main reason for which internal combustion engines have flywheels on the crankshaft, to keep the pistons moving through the dead centers."

And a V8 wins the 720 degree game

 

[ZeeOSix]

Stopped is not when V=0, its when dx=0 for some dt > 0. You have the definition of "stopped" wrong.

Go back and read what I said earlier. I said V=dx/dt and V=0 (also known as "stopped") when dx=0 and dt equals something more than zero. Exactly what you just said.

If the crank never stops rotating, then by physics its not possible for the pistons to ever stop moving. The pistons and crank never NEVER decouple. Or perhaps you think so, so you can show me how that happens too?

Wrong ... never said pistons "decouple" from the rods, lol. Don't go obtuse, on both accounts.

 

[ZeeOSix]

What post # for this graph?

Apparently you don't read everything ... not good if you want to actually participate in a technical discussion, lol

 

[ZeeOSix]

And if you read my post I said "very well then........", the max speed not at 90 due to the combustion profile. Did you see that post?

Yeah, AFTER I posted my response. Good you owned up to being wrong.

 

[ZeeOSix]

Ah, post #393.
It says "shows where velocity is zero for a small time".

Really. not that I can see, it shows where the speed of velocity crosses over a single point of zero. I do not see any delta-t there.

How do you think a line magically crosses through the zero velocity point without there being some small dt going on there? Time warp perhaps, lol. And again, the dt would depend on the crank RPM. Do your own graph with the engine turning at 1/500 of a RPM. You think you'd see a dt there when the velocity curve went through the zero axis?

 

[EMPIRE]

Apparently you don't read everything ... not good if you want to actually participate in a technical discussion, lol

I saw it.

Let me ask a good Q. Because I know what the graph is not....... can you tell me how the graphs might change if say the engine had 36 or 72 pistons? I have an idea, but would like to understand it more.

 

[EMPIRE]

How do you think a line magically crosses through the zero velocity point without there being some small dt going on there? Time warp perhaps, lol.

dt=0 at that point where v=0, dt=0 at every point on the graph. This is how we look at a time slice, we make dt=0, which fixes the observation to some time (t).

 

[ZeeOSix]

Your post #393 says speed is zero for some small time. How much time passes when speed stays zero?
What was the time period for V=0 ?? I am interested in knowing.

See Post #490.

 

[EMPIRE]

Wrong ... never said pistons "decouple" from the rods, lol. Don't go obtuse, on both accounts.

If they do not decouple, then they are coupled, thus a movement in crank is a movement in piston. That's what it means.

 

[EMPIRE]

See Post #490.

see #492

Maybe this will help some?
http://wearcam.org/absement/Derivatives_of_displacement.htm

 

[ZeeOSix]

At top dead center (TDC) and bottom dead center (BDC), the piston is completely stationary for a split nanosecond and at boundary lubrication. Kinetic friction is at play and the additive package is doing the lubrication work. Up to approximately 20 degrees either direction from TDC and BDC, the piston is transitioning into mixed lubrication and rides in full hydrodynamic lubrication (dynamic friction) through the rest. The ring tension has the greatest effect on kinetic friction at TDC and BDC and ring thickness plays a larger role in how quickly and efficiently the rings transition into and ride in full fluid lubrication. The wrong oil for the ring thickness and tension can mean the rings don't get up in hydrodynamic lubrication like it should or increase oil transport past the rings (increasing oil consumption) or even possibly excessive lifting/loading of the rings causing them to flutter and effect ring seal. The type and style of hone on the cylinder walls can play a factor also.

Good stuff, and also factors in ring and cylinder wear near TDC and BDC. TDC is much worse because of the heat of combustion making it an very hash environment for oil.

 

[ZeeOSix]

I am very interested in knowing the quantitative value of the small time period where v=0, for any rpm.
How small was the time period? Was it 2nsec, was it less than that, was it more than that? If the observation is say just 1nsec, then wow, that's some very very fast data acquisition sensors and software, it would need to be faster than 1GHz.

Guess you're not very familiar with modern testing techniques. Maybe contact the SWRI and talk to them about how they measure all kinds of internal components on ICEs. And as already mentioned, it can be done with kinematics like I linked to earlier. Use the equations in that link. Write a computer program and look at the outputs as the engine RPM changes.

 

[EMPIRE]

So, the ICE piston stuff is neat, but I dont see where it accounts for the variable forces of 8x combustions. The combustion kicks change a lot of the dynamics. As example, the avg rpm may be constant, but take a look at smaller delta-t's and you see the rpm changes (just a bit) 4x per 360.

 

[ZeeOSix]

If they do not decouple, then they are coupled, thus a movement in crank is a movement in piston. That's what it means.

That's where you seem to be "decoupled", so to speak. Just because the crank is moving doesn't mean the piston doesn't stop for a slice of time.

 

[ZeeOSix]

I saw it.

Let me ask a good Q. Because I know what the graph is not....... can you tell me how the graphs might change if say the engine had 36 or 72 pistons? I have an idea, but would like to understand it more.

Has nothing to do with the conversation - that graph is for one piston regardless if an engine has 1 piston or 200 pistons. They all do that same basic motion.