Keep her above 4000rpm and she'll thank you for it every day.

[Paul]

Found it, it's 3.07 inches.

4000 rpms = 2051
5000 rpms= 2563
6000 rpms = 3076
7200 rpms = 3691

[Brucelee]

Originally Posted by Paul

Found it, it's 3.07 inches.

4000 rpms = 2051
5000 rpms= 2563
6000 rpms = 3076
7200 rpms = 3691

Good info. Mass times velocity SQUARED equals momentum.

Every time the piston goes down, it has to be pulled back up.

[Brucelee]

Brucelee, what's the source of failure in this case? Is something breaking from stress or is it breaking from wearing out? I would bet that it's the former. You have to look at the cause for this to be useful information.

I believe that the amount of STRESS that you place on a motor contributes to it wearing our or breaking.

I don't think that there is any question that a bearing is stressed more at high rpms vs low rpms, all things being equal. Ditto, connecting rods, pistons, valves, etc.

That is why racing oil is developed, to deal with unique stresses that normal motors don't experience.

[blue2000s]

Are you trying to change the focus of the back-and-forth?

There was a comment made on wear, I made my statement about the study on wear, showed a review and synopsis of the study that was conducted by a technologist at GM, described why it's true, and the next comment was off topic. What happened there?

[blue2000s]

Originally Posted by Brucelee

Brucelee, what's the source of failure in this case? Is something breaking from stress or is it breaking from wearing out? I would bet that it's the former. You have to look at the cause for this to be useful information.

I believe that the amount of STRESS that you place on a motor contributes to it wearing our or breaking.

I don't think that there is any question that a bearing is stressed more at high rpms vs low rpms, all things being equal. Ditto, connecting rods, pistons, valves, etc.

That is why racing oil is developed, to deal with unique stresses that normal motors don't experience.

Stress leads to fatigue, wear comes from friction, these are two totally different mechanisms.

Racing oil is developed to increase the amounts of additives needed for the best lubrication. Highway use vehicles have laws on the additives that can be added, racing cars don't.

[blue2000s]

Originally Posted by Brucelee

Good info. Mass times velocity SQUARED equals momentum.

Every time the piston goes down, it has to be pulled back up.

momentum is actually 1/2 x mass x velocity squared.

[Brucelee]

Originally Posted by blue2000s

momentum is actually 1/2 x mass x velocity squared.

================================================== ==================

My head hurts!


I have found conflicting anwers to the formula for momentum. It seems physics is not that precise after all.



Deborah,
First, energy and momentum are very different properties.

An object takes time to stop moving. The momentum of an object can be
describes as the amount of force required to stop the object in one second.
When a constant force is applied to an object, it is the force multiplied by
the time over which it is applied that yields the change of momentum of the
particle. Also, momentum is a vector: it has a direction to it. Momentum
points in the direction of an object's velocity.

An object continues to travel while its velocity drops to zero. The kinetic
energy of an object can be described as the amount of force required to stop
the object over a distance of one meter. When a constant force is applied
to an object, it is the force multiplied by distance traveled along the SAME
AXIS as the force that determines the change of kinetic energy. Kinetic
energy is a scalar: it has no direction.

An object changing direction but neither speeding up nor slowing down is an
example of changing momentum but not changing kinetic energy. If the object
does speed up or slow down, both momentum and kinetic energy will change.
For example, consider throwing a rock upward at a certain speed. If you
double the rock's initial speed, the rock will require twice the time and
four times the distance to reach zero speed. Thus, the rock with the
doubled speed has twice the momentum and four times the kinetic energy.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College

Momentum is m*v, and kinetic energy is m*v*v/2, so if momenta and energies
are the same, we have:
1) m1*v1 = m2*v2
2) m1*v1*v1 = m2*v2*v2
using (1) in (2) yields
m1*v1*v1 = (m1*v1)*v2 -> v1 = v2
using this in (1) shows that m1 = m2
So, yes, if a particle has the same momentum and the same kinetic energy
as another particle, their masses and velocities must be equal

But having the same momentum does not by itself imply having the same
energy. A heavy particle moving slowly can have the same momentum as
a light particle moving swiftly.

--
Tim Mooney
Advanced Photon Source, Argonne National Lab.

[Brucelee]

Stress leads to fatigue, wear comes from friction, these are two totally different mechanisms.

Are you suggesting that stress does not lead to wear? If I incease the stress on a bearing are you suggesting that it does not wear faster than if I lower the stress? Are you suggesting that engines that are supposed to run at very high piston speeds don't need to be engineered to handle the stress?

Are you suggesting that if I run my Boxster at 6K rpm, that concussion, heat, friction, and mechanical stress are not all higher than if I run it at 3K RPM? What about the impact of higher temps on metal fatigue?

I can't see any way out of this for you. Explain how all the factors that contribute to metal stress and wear are not higher at higher piston speeds and higher RPMs.

[Lil bastard]

WOW! Very passionate arguements!

But, really, it's only academic or philosophical because too many assumptions are being made for the stated arguement to have any real world relevance.

Nothing is noted about the type of lubrication - not all motor oils provide the same level of lubrication and protection under high RPM use.

Nothing is noted about the filtration system (filter) used or whether different filters change the equation - they do - see: Barris, M.A. (1995). "Total Filtration: The Influence of Filter Selection on Engine Wear, Emissions and Performance". SAE Fuels and Lubricants (Paper 952557)

Nothing is noted about the lubrication system flow capability and variances under differing RPM ranges.

Nothing is noted about the ambient operating temperatures or temperature ranges for this high rpm operation.

Nothing is noted about the cooling system efficiencies at high RPMs or whether the levels of coolant pump cavitation at varying RPMs have an effect on wear - they do.

Nothing is noted about the varying valvetrains and their contributions to increased wear at high RPMs.

Fuel Quality, Gen'l Engine condition, Driving Habits, Load, and on and on...

As I read this, there are simply too many unmentioned or unquantified variables to produce a soletary conclusion to this arguement.

Each side will continue to produce out-of-context or non-relevant technical data or references to try and eek some further validation of their expressed view and ample, endless, tidbits exist out there to prolong the arguement indefinitely with no chance of reaching a reasonable conclusion.

Nor does it seem, are the parties involved capable of being swayed by the arguements made by the other side. People it seems will go away believing pretty much what they did as they entered this discussion.

I mean, there is not even a concensus on this issue among qualified experts, how could we possibly hope to produce one here?

So, really, IMHO, it's time to slap the lock on this thread - I mean 87 replies over 5 pages and no end in sight!

Time to get back to Boxstering - at whatever RPM Floats your Boat.

[Brucelee]

Originally Posted by Lil bastard

WOW! Very passionate arguements!

But, really, it's only academic or philosophical because too many assumptions are being made for the stated arguement to have any real world relevance.

Nothing is noted about the type of lubrication - not all motor oils provide the same level of lubrication and protection under high RPM use.

Nothing is noted about the filtration system (filter) used or whether different filters change the equation - they do - see: Barris, M.A. (1995). "Total Filtration: The Influence of Filter Selection on Engine Wear, Emissions and Performance". SAE Fuels and Lubricants (Paper 952557)

Nothing is noted about the lubrication system flow capability and variances under differing RPM ranges.

Nothing is noted about the ambient operating temperatures or temperature ranges for this high rpm operation.

Nothing is noted about the cooling system efficiencies at high RPMs or whether the levels of coolant pump cavitation at varying RPMs have an effect on wear - they do.

Nothing is noted about the varying valvetrains and their contributions to increased wear at high RPMs.

Fuel Quality, Gen'l Engine condition, Driving Habits, Load, and on and on...

As I read this, there are simply too many unmentioned or unquantified variables to produce a soletary conclusion to this arguement.

Each side will continue to produce out-of-context or non-relevant technical data or references to try and eek some further validation of their expressed view and ample, endless, tidbits exist out there to prolong the arguement indefinitely with no chance of reaching a reasonable conclusion.

Nor does it seem, are the parties involved capable of being swayed by the arguements made by the other side. People it seems will go away believing pretty much what they did as they entered this discussion.

I mean, there is not even a concensus on this issue among qualified experts, how could we possibly hope to produce one here?

So, really, IMHO, it's time to slap the lock on this thread - I mean 87 replies over 5 pages and no end in sight!

Time to get back to Boxstering - at whatever RPM Floats your Boat.

Again, we are just having a theoretical disussion, there is no argument per se.

The assertion made was that running the Boxster engine at high rpms (to red line every day) is GOOD for the engine. Cleans out carbon etc. The implied converse is, the engine is built for high RPMs so NOT running at high RPMs is bad for the engine.

I assert this is not and cannot be true.

There are tons of mitigating factors. However, I would like someone to explain how heat, friction, stress and wear are all not HIGHER at higher RPMs and piston speeds. I think this would take a repeal of the laws of physics and engineering.

BTW- I used to set my oil temp gauge on the C5 and when I ran it at high RPMs, the oil got hot and quickly. The cooling system kept the car OK, but the innards of the engine were getting quite toasty.

I may be wrong but when an engine is designed to run high horsepower, high RPMS, they always beef it up in design. If RPMS were GOOD for the engine, they would not need to do this.

When an engine is designed for high RPMs, I don't think they look for a cheap grade oil, they spec synthetic etc. In other words, they try to accomodate the high RPM, piston speeds, etc. They must do this for a reason, no?

My point is, it is fun to run your engine hard, how fun is a track day! :
However, just be honest, this fun comes with a risk. To deny this seems disingenuous.


D

[Lil bastard]

Originally Posted by Brucelee

Again, we are just having a theoretical disussion, there is no argument per se.

The assertion made was that running the Boxster engine at high rpms (to red line every day) is GOOD for the engine. Cleans out carbon etc. The implied converse is, the engine is built for high RPMs so NOT running at high RPMs is bad for the engine.

I assert this is not and cannot be true.

There are tons of mitigating factors. However, I would like someone to explain how heat, friction, stress and wear are all not HIGHER at higher RPMs and piston speeds. I think this would take a repeal of the laws of physics and engineering.

BTW- I used to set my oil temp gauge on the C5 and when I ran it at high RPMs, the oil got hot and quickly. The cooling system kept the car OK, but the innards of the engine were getting quite toasty.

I may be wrong but when an engine is designed to run high horsepower, high RPMS, they always beef it up in design. If RPMS were GOOD for the engine, they would not need to do this.

When an engine is designed for high RPMs, I don't think they look for a cheap grade oil, they spec synthetic etc. In other words, they try to accomodate the high RPM, piston speeds, etc. They must do this for a reason, no?

My point is, it is fun to run your engine hard, how fun is a track day! :
However, just be honest, this fun comes with a risk. To deny this seems disingenuous.


D

Well, I don't want to get sucked into this Black Hole, so I'll just posit this thought and be done with it.

I'm not sure I agree that High RPM engines are 'overbuilt'. Typically, if anything, they are 'underbuilt' to lighten the reciprocating mass in order to facilitate the high RPMs.

High HP motors may be another story.

Further still, High RPM/High HP Production motors also meant to meet a certain reliability criteria may be yet another entirely different story altogether.

My own personal belief system says that higher stress equates to accelerated wear, but I'm no self-proclaimed expert on the subject.

[Darkhamr]

LOL who dug this old thread up? And are people seriously trying to argue that driving at higher average rpms will extend the life of your engine?!?!

[teacher]

wow, I didn't think that my little post would cause such a debate!