Perrin light wieght pulley

[steve99]

Ill try to go simple


An engines power comes from the combustion process. this is not changed when you change pulleys flywheels etc.


Their will be losses due friction of the various rotating and reciprocating parts.


Flywheels , pulleys crankshafts ect are energy stores. They don't "make" power but they can store and return power (energy). One of their function's on an engine is to smooth the "pulses" of energy/power created as each cylinder fires and to store some energy so its easier for you to take off from a standstill and to keep the engine rotating "smoothly" especially at low rpm.


Talk to anyone with a manual car that installed rearly light flywheels about taking off and rough idle.


If your accelerating a car on a dyno the major part of the mass of the car is stationary. The only thing your accelerating is the engine and driveline components.


If you install lightweight driveshafts/wheels/flywheels/pulleys ect you may notice a slightly quicker ramp up as your accelerating on a dyno. due to the reduction in rotating mass that you have to accelerate. remember your not accelerating the other 1200kg of car on a dyno.


You notice this as the driveline components accelerated when the car is on dyno is maybe 200kg or so not the 1400kg of car. so the 5kg you shed has a more noticeable effect.


But the peak power value should be identical as the same engine combustion process is producing the power and the friction losses should be same. you may notice some slight difference due to the way inertial dynos measure power.


Now take the car off the dyno and in the real world, the 5kg you shed is only 5kg/1400kg , and you wont notice it.


you will likely notice that heal and toe downshift (clutch disengaged) , with unloaded engine will rev quicker.

[tofurun]

I am sorry.... I have created Armageddon.

[humfrz]

Originally Posted by tofurun

I am sorry.... I have created Armageddon.

...............


(now, just don't ask anything about octane)



humfrz

[tofurun]

Originally Posted by humfrz

...............


(now, just don't ask anything about octane)



humfrz

Does this include flex fuel questions????

[humfrz]

Originally Posted by tofurun

Does this include flex fuel questions????

Those are OK ....... in a separate thread ....... this thread is wound up tight enough already ......


humfrz

[tofurun]

Originally Posted by humfrz

Those are OK ....... in a separate thread ....... this thread is wound up tight enough already ......


humfrz

In all honesty I feel like this thread will be an amazing read for year models to come lol.

[justatroll]

Originally Posted by ysu

I understand that you're looking for a physicist to explain it to you, I'm not a scientist as I said, and very much not a teacher, and I think that's who you'd need to get this explained properly. This is as far as I can go

We don't need a "scientist" to answer a classical physics problem.
Scientists work on unsolved problems, engineers work with natural laws that are already accepted as truth.
All complex problems can be broken down to the most basic element.

Please either agree with, or dispute (with facts) the following:

Originally Posted by justatroll

Axiom 1 "HP can be measured at constant angular velocity"
Axiom 2 "rotational inertia is not a factor in systems rotating at constant angular velocity"

Inference "Rotational inertia is not a factor in HP measurements at constant angular velocity."

One must either agree with the above or not.
If you disagree with the above then we cannot proceed.

If you agree, then as we continue the discussion about dynos and accelerating rotational masses, you cannot change your position on the above inference.

The definition of Brake Horsepower actually Includes the statement:
re: 'brake' horsepower measurement:
"Brake refers to the device which was used to load an engine and hold it at a desired rotational speed. During testing, the output torque and rotational speed were measured to determine the brake horsepower."


Here is a direct cut & paste from the SAE standard for horsepower measurements (SAE J1394 'Engine Power Test Code- Net Power Rating' updated 2008 - cannot download the most current without paying for it)

" 7.5.2 TEST POINTS
Measurements shall be taken at increments of no more than 500 RPM in sequence from the lowest to the highest engine speeds recommended by the manufacturer. The operating speeds shall include those for peak power and peak torque. Data at 100 RPM increments around peak torque and peak power are recommended to accurately distinguish their respective rated speeds. Engine speed shall not deviate from the nominal set speed by more than ±1% or 5 RPM, whichever is greater.
7.5.3 LOGGING OF MEASUREMENTS
No data shall be taken until torque and speed measurements have remained stable within 1% and controlled temperatures have remained stable within ± 2 C for at least 1 minute. The recorded measurements shall be the average of readings over a span of 1 minute. Alternatively, data can be taken by stabilizing the torque and speed for 5 seconds and then acquiring data at a minimum 10 Hz rate for at least ten seconds. If this alternative procedure is used, the entire speed sweep shall be repeated at least three times. The results are considered valid if the repeatability of at least three measurements is within 1% of the mean."

The SAE Standard is telling us right there to make the torque measurements at constant RPM and stabilized.

Or are you going to argue with the accepted standard now?


Regarding your misunderstanding of the physics, please see the following.

It is a fundamental law:

Work is Force Times Distance: Work(N-m) = Force(Newton) X Distance(meter). The units are in Joules (J).
Joule = It is equal to the energy transferred (or work done) to an object when a force of one newton acts on that object in the direction of its motion through a distance of one meter (1 newton metre or N·m).

In the case of a dyno, it is measuring the torque and the RPM at a discrete point in time.
It then performs the calculation for work, but for a rotational system, the work is not Force X Distance but Torque X Rotation.
(for clarification see: http://www.dummies.com/how-to/conten...onal-work.html)

So Work = T(n-m) X Rot(radians per second) (OR T(ft-lb) X Rot(RPM))

So we now know the steady state work being performed at that instant in time by the torque trying to accelerate the system (but failing to accelerate because the dyno is HOLDING IT at constant RPM).
So we have the Watts (Joules per second) that the engine is putting out at a discrete point in time. This is NOT the power YET.

To calculate the Power:
Power = Work / Time

P(hp) = (T(ft X lb) X N (rpm)) / 5252

The constant 5252 is the rounded value of (33,000 ft·lbf/min)/(2π rad/rev).

This results in the power output of the system (in Joules per second) while rotating at a constant rate.
The 'per second' has absolutely NOTHING to do with acceleration.

As I stated previously the units of "velocity" is 'meters per second'.
Just because a unit has a per second in it does not mean it has anything to do with acceleration.

I try to keep it civil, but....
My actual title is "Principal Test Engineer" with >20 years experience.
The test article I am currently personally in charge of cost more than a nuclear submarine.
I could ask our lead mechanical engineer to explain it to you, but she would give the same answer.
In fact the mechanical engineer intern I am currently training would give the same answer (or I would send him back to school).

[nikitopo]

Guys.. we have different opinions, but the last was not a good behavior ..

[ichitaka05]

I heard there was an Armageddon?

...did I miss it?

[justatroll]

Originally Posted by nikitopo

Guys.. we have different opinions, but the last was not a good behavior ..

Please point out the lack of good behavior.

Are you chastising me again for using facts?

[G-awesome]

I feel like I'm watching an episode of the big bang theory watching scientists (in this case, engineers) debate scientific theories until it goes right over my simpleton head.

[nikitopo]

You mentioned it yourself:

"I try to keep it civil, but...."

If someone doesn't agree with you, is this your way to solve the difference? All of what you're saying has a meaning, but is not relevant with what we measure in reality in cars. All the dynos measure torque and hp with the car under WOT. Someone said that the weight of the car is not accelerating on a dyno. This is also incorrect. Did you ever tried to run using a corridor? You were not accelerating? What you were doing? Flying?

As said before it is a personal preference for someone to use or not to use a lightweight pulley. Some might like it and some others might not because it changes the driveability of the car. Others have objections about the safety of the engine. This is also understandable! Additionally, not all of us are "sensitive" on changes and a gain of 6-8whp might not be always noticeable. However, we have to show some respect to companies selling these parts for many many years. Want to name a few? Perrin, Cusco, Toda, ...

What do you want to say? Are all these companies cheating the people?

[justatroll]

Originally Posted by nikitopo

You mentioned it yourself:

"I try to keep it civil, but...."

The ONLY reason I prefaced myself with that statement was because I was about to throw my credentials around which is considered rude (I guess) only if you are an engineer.

Originally Posted by nikitopo

If someone doesn't agree with you, is this your way to solve the difference?

No I present facts and ask for someone to present facts that counter mine, or a counter-argument.

Are you going to dispute my quotes from the SAE document that tells you how to perform HP tests?

Originally Posted by nikitopo

What do you want to say? Are all these companies cheating the people?

Yes - They are cheating the average joe that isnt building a race motor.
And IF I was to build a FA20 race motor I would use the heavier fluiddampr anyway.
The only boxer race engine I have ever built has a giant fan on the front of the engine, so a fluidamper doesnt work.

AND

Originally Posted by nikitopo

Someone said that the weight of the car is not accelerating on a dyno. This is also incorrect.

That is absolutely correct as the car does not move as the dyno run is performed.
It IS in the same room as where it started is it not?
The car has not accumulated any kinetic energy like it would if it was moving down the road.

[churchx]

You accelerate only rotating parts on dyno, so really, vehicle weight has nothing to do with dyno readings, as it stays stationary hooked on and you don't have to spend energy to overcome car's mass inertia, just energy to spin up rotating items and overcome dyno's roller inertia or roller brakeforce. Yes, there will be reduction in energy needed for spun parts, but it won't be there one dyno charts, as on charts you don't have time on scale, just power/torque on one scale and rpm-s on other scale. If one of scale would be time, then yes, you would see improvements on acceleration/time to get to speed. But it's not there.

As for big name vendor mention for lightened pulleys .. depends on what customers buying those want .. imho they rather may get it for quicker reving / easier revmatch, not for very slight (due little weight of pulleys and rotating mass not placed far from rotational center) improvement in acceleration. Or because those parts are just one of many in long list, where one lightens car by lightening anything one can. Or for ones that put it mostly for bling purposes or bragging rights, JDM yo! . If there is demand (for whatever reason), there will be supply. Even if price/performance gains sucks. You know of TRD fuel cap, don't you? Gains from lightening heavier items or with mass further from rotating center are bigger (eg. wheels, flywheel) and might be noticed also by butt dyno .. but then again they won't show up on dyno charts too.