Noak and wear

[Shannow]

Originally Posted By: CATERHAM
If that's your explanation for your assertion that heavier oil flows faster through an engine than lower viscosity oil it doesn't explain the lower system back pressure that lower viscosity allows.


You haven't read and understood a word that I've posted, or are purposely (again) creating a strawman argument.

A lighter oil will have a lower volumetric flow rate from a positive displacement pump...it will not and cannot flow more, which is your assertion.

However, of course a thinner oil will have a lower backpressure...the same (or slightly less) volume flows with less restriction.

I have NEVER argued to the contrary, in spite of your assertions

 

[Shannow]

Originally Posted By: turtlevette
6200lbs is an impulse load that decays quickly during the power stroke. Also understand not every rotation is loaded. I think we need to average the load which is what I was trying to do by just taking the peak torque and using that. Using the peak impulse load inflates the numbers.

It sure isn't a simple calc. I've made mention to Shannow before that a turbine is a much simpler solve because the loads are smooth and steady in one direction.


Torque is NOT A FORCE...therefore you can't use it as one.

You've explained (and I've explained before) that bearings have cyclic load...it's not the simple case.

However, the discussion is where it is, because of your assertion that speed has minimal impact on bearing flow...which argument was destroyed, at which you play David Copperfield "look over there", while failing to acknowledge that your original, intuitive I might add, not scientific, assertion was wrong.

 

[JAG]

I'll try to explain something by using an example of someone pumping water from a well and assuming that each stroke of the pump moves a constant volume of oil per second (to mimic a positive displacement oil pump. The guy pumping the well is forced to operate the pump at a constant rate no matter the viscosity of the fluid in the well. When a more viscous fluid is put in the well, it takes him more force to maintain the constant pump rate and corresponding constant volumetric flow rate. That is entirely because of the higher pressure needed to force the oil out at the constant rate. Does that help?

Using the constant current example that Shannow mentioned, a thicker oil is like having a wire with higher resistance. I = V/R, so to maintain I constant, V must increase. V is analogous to pressure.

 

[OVERKILL]

Originally Posted By: turtlevette
Originally Posted By: CATERHAM
and therefore with greater flow.

And the difference in back-pressure between a light 20 grade and say a 50 grade is substantial, as much as a 50%. Does that mean the 20 grade oil will flow 50% more oil? I don't know, there could be other leaks within the oil pump itself but I'm of the opinion that a good portion of the reduced back-pressure is a result of less restricted oil flow afforded by the lower viscosity oil.


If the bypass is closed throughout the rpm range at operating temp, how can that be?

I'm on your side on this, and have been trying to prove the bypass is open through most of the rpm range. Shannow thinks the pump flow almost exactly matches the dynamic flow requirements of hydrodynamic bearings which I don't buy. I don't know for sure who is right at this point but I'm not as sure of my stance now.

That's the reason for all the extraneous discussion. It all hinges on that. Maybe a new thread needs to be opened on that subject.

Noak vs wear has gone by the wayside.






I think that's an excellent idea. If we are going to do that, let us keep it civil and respectful and then perhaps it can continue the course of this thread, which has calmed down and resulted in some really great points being brought up

 

[yvon_la]

I think you guys forget one single very easy constant !the max pressure cant be more then what the various kind of seal can absorb (probably around 60 lbs.)trucks max around 50 ish cold .so they re probably close to max .so if max pressure is defined anything related to pressure become irelevent .only other variable that might be variable is flow in gallon per minute this is also limited because of size and viscosity ,so whats left?

 

[yvon_la]

Ok who gave these guys hydraulic engineering handbook?there is no way one person would buy a hydraulic engineering handbook for 200$ (or whatever the new name of the thing is)

 

[yvon_la]

From my experience (versa note 2014 almost no mile)5/20 ep (mobil)is way noisier then stock ,so,in my book whatever theory say the oil has a issue (when at operating temperature)(midway)so i ll probably revert to 30 (probably will try 0w30 or better delvac1 le 5w30 if i can ever find some .hear your engine,if it sound metallic (and you know the oil hasnt silicon(wich it shouldnt by the way)then the oil has an issue .dont sweat it at normal operating temperature trust your hear (if they re still good )they dont lie.

 

[CATERHAM]

Originally Posted By: JAG
I'll try to explain something by using an example of someone pumping water from a well and assuming that each stroke of the pump moves a constant volume of oil per second (to mimic a positive displacement oil pump. The guy pumping the well is forced to operate the pump at a constant rate no matter the viscosity of the fluid in the well. When a more viscous fluid is put in the well, it takes him more force to maintain the constant pump rate and corresponding constant volumetric flow rate. That is entirely because of the higher pressure needed to force the oil out at the constant rate. Does that help?

The problem I see with this analogy is that while it explains the increased work required to pump thicker oil it doesn't take the increased resistance of forcing the thicker oil through the engine bearings into account. The increased system back-pressure may compensate in part for the increased resistance to flow that the higher viscosity oil is providing but there still would be less net oil flow.
If there was no relief valve limiting the pressure build-up in the system I posit that the oil's viscosity could be increased in theory to the point that no oil would be able to flow through the engine at all.

 

[OVERKILL]

Originally Posted By: CATERHAM

The problem I see with this analogy is that while it explains the increased work required to pump thicker oil it doesn't take the increased resistance of forcing the thicker oil through the engine bearings into account. The increased system back-pressure may compensate in part for the increased resistance to flow that the higher viscosity oil is providing but there still would be less net oil flow.


There cannot, without a bypass/relief event occurring, be less flow. There cannot. That violates the definition of what a positive displacement pump IS.

Originally Posted By: CATERHAM
If there was no relief valve limiting the pressure build-up in the system I posit that the oil's viscosity could be increased in theory to the point that no oil would be able to flow through the engine at all.


If there's an orifice, it will flow, otherwise something is going to explode because if you remove the ability for a positive displacement pump to relieve pressure, by the very nature of it being positive displacement, it is going to continue to move fluid at the same rate. Where it moves it is of no consequence to to the pump. So it will explode the filter or find whatever the weakest link in the system is. This assumes you don't break the driveshaft for the pump or shear off the keyway of course.

 

[Shannow]

Originally Posted By: CATERHAM
The problem I see with this analogy is that while it explains the increased work required to pump thicker oil it doesn't take the increased resistance of forcing the thicker oil through the engine bearings into account. The increased system back-pressure may compensate in part for the increased resistance to flow that the higher viscosity oil is providing but there still would be less net oil flow.
If there was no relief valve limiting the pressure build-up in the system I posit that the oil's viscosity could be increased in theory to the point that no oil would be able to flow through the engine at all.


Strawman argument, as what you are describing is not a set of circumstances pertaining to lubrication of an engine, but a hypothetical "what if I sabotaged the system by doing "x" ", what would be the failure mode...it's common in second and third year undergrads, who are exploring how systems work.

"what would happen if I blocked the relief ?"
"what would happen if I put too thick oil in ?"

What would happen in your overly thick, no bypass "engine" is that the positive displacement pump would move it's displacement of oil through the orifice and the bearings, at (again) a slightly higher volumetric efficiency than a thin oil under the same discharge pressure.

Either the "lubricant" would flow, or it will stress either the pump, or the "engine" to the point that something bursts and it continues to flow it's volume per revolution.

If you are talking pumping solids, again, they don't leak as much as thinner oils.

 

[yvon_la]

I don't know how to explain it!is it possible then that a filter discharge occur (not voltage wise)but like in certain configuration (liker mine the filter is mounter horizontaly and its a fram ultra 6607)is it possible for it to get emptied for some odd reason (exemple:like if a brake need to be bled if you don't want issue)I don't know how to explain it but at time the engine sound awesome cold or hot ,and at other it sound like everything is running without oil!since I don't own a decibel meter to put in engine bay I cant prove what I am saying,but it seem like at time there is a depressurization ,like if this and that and that concord depressurization (or lack of oil)occur.its very subtle so it would be easy to miss,the only reason I noticed it is because I drive very old truck 1999,and similar thing occurred but my problem was elsewhere.sorry if I cant be more clear ,its a subtle sound and it isn't always happening so it is hard for me to explain.only thing I could think that is so random like this is static electricity but last I check it didn't make engine run like it is running with a 50% filled oil filter

 

[JAG]

Originally Posted By: CATERHAM
The problem I see with this analogy is that while it explains the increased work required to pump thicker oil it doesn't take the increased resistance of forcing the thicker oil through the engine bearings into account. The increased system back-pressure may compensate in part for the increased resistance to flow that the higher viscosity oil is providing but there still would be less net oil flow.

The analogy does indeed have pipes that are a source of resistance to flow, which correspond to engine bearings and every other engine passageway. I recommend that you read up on the basics of fluid flow and then read the positive displacement pump thread by KrisZ in the mechanical forum.