of course i get that .
So you put an engine on an engine dyno and get 200 fwhp at 8000rpm .
Now you put it in the car andonto a chassis dyno and you get 160wheelhp at 8000rpm .

You don't accelerate the engine - it is just sitting there making 160whp . Does it make any difference how heavy the flywheel is as to how much wheel hp it is making ?

I'll give you a clue - answer starts with N

where did the 40hp power go ? frictional losses !

 

Paul is cheating. Brettus cant argue anymore if he gets killed when the weights fly off his driveshaft.

 

not at a static RPM. so tell me, how often do you track your car and never have any RPM change for the entire event? its not about how much total power is made, its about how it is delivered. and by definition it is parasitic loss. again, go learn the physics behind why, and yes N stands for nincompoop, dont be one

 

you are confusing frictional loss, with drivetrain loss which includes both frictional and angular momentum losses


you think all the super high dollar motorsports light internals and rotating parts are just to remove a couple of pounds of static weight? no, its to remove rotational weight which has a MUCH larger effect of power delivery than removing static weight

 

fixed

 

No - you are .

You have drivetrain losses - frictional . Then you have losses associated with acceleration - which relate to the mass of all the rotating parts along with the weight of the car

 

I am convinced the laws of of physics are reversed south of the equator - do toliets really spin backerds down under?

 

Actually... no
Its the angle the holes around the rim are drilled that determines how the water "spins" around the bowl.
Sorry... too much Science Channel...

Back to the Drivetrain Loss argument!

 

Paul - answer this please ....


You don't accelerate the engine - it is just sitting there making 160whp . Does it make any difference how heavy the flywheel is as to how much wheel hp it is making ?

 

actually, angular acceleration of drivetrain parts in NO WAY relates to static mass of any other part of the car.

and its nice to know that your drivetrain sees no acceleration during operation.

the reason(im guessing) CRH didnt get deep into this is because its difficult to explain to someone who doesnt understand the physics. does removing 10 pounds of rotational weight equate to more total power at any given rpm? no. what it does, it later the delivery of the torque/power curve which is just as important unless you manage to compete on the track by waving around a dyno sheet with the curves blurred out and only showing the max TQ/HP

i cant walk you through the physics, its not as simple as a static number, or a percentage. like the link i gave you, its Intergral math.

understand it, accept it, figure it out, or deny it. at this point i'm starting to care less what you think

 

On a basis of perspective (theoretically, assuming you could see through the ground to the other side of the planet), it is accurate to say they spin "backwards".

 

You aren't listening - jeez
stop your posturing and just answer the question .


You don't accelerate the engine - it is just sitting there making 160whp . Does it make any difference how heavy the flywheel is as to how much wheel hp it is making ?

 

one last time for the amusment of some others who i know are laughing at this...


at a static rpm, all you have is frictional loss. as soon as your drivetrain changes rpm, you have to deal with angular momentum. so unless your only concerned with being a freaking dyno queen for max HP/TQ, or you live on the other side of a black hole, this matters.

what your saying is right, but its not the whole picture, or even the important part

 

If I cared to argue with that I would search for the episode I watched where they had a toilet cut down to show you how it works and why its a myth.
But since its not a big deal to me, I'll let you believe what you want.

 

Simple proof: Take a piece of translucent paper, and draw a circle with an arrow on it, then flip it around.

EDIT: It's a given that the shape of the bowl and water inlet ducts will influence the spiraling of the water. The "myth" is simply perpetuated by the play on the basis of perspective I previously mentioned.

 

i am listening, and i've answerted this like 3 freaking times man. god damn.

1) if your drivetrain rotates at 9000rpms it does not matter if the flywheel weighs 10lbs or 10,000lbs. at 9000 rpm the TQ/HP will be the same.

2) in the real world we have to accelerate our drivetrains up to 9000rpms starting at 0rpms. and unless your drivetrain is massless, you have a Moment of Inertia whch is a measure of an object's resistance to changes to its rotation. See that word, resistance? The heavier something is that rotates, the more energy it takes to accelerate its rotation. How do you not ******* understand this?

 

This argument is not about what difference rotaional mass has on acceleration it is about DRIVETRAIN LOSS as measured by a dyno . A dyno does not measure losses due to acceleration of mass . You could have a ton of weight strapped to the driveshaft and it would not change the number you get .

Why ? When you do a dyno the acceleration is so slow that rotational acceleration is not a factor .

There is virtually zero loss "as measured by a dyno" from the flywheel . Correct or not ?

 

this is typical teenager ricer/dynoqueen mentality, you should be beyond this.

for the last time before i write you off as an idiot in my mind:

at a static RPM, ie the RPM where you're getting your "dyno number", it doesnt matter what the drivetrain weights are. this is correct, this is also not the whole picture OR the important part.

as you add mass to anything rotational, or if you move the mass away from the axis of rotation, the laws of freaking physics defines that it takes more energy to alter the angular velocity. this is called angular acceleration. and what it does is change the shape of your curves on the plot, not the final peak number.

 

wow this has turned into an episode of 'Big Bang Theory' , HAHAHA

I much like this better then people hating on me..... lol

 

until you can either DO the math behind this, or at LEAST pretend you understand it, you have no basis to claim this. not to mention you're wrong.

not to mention that the last time i checked, we drove on roads, and tracks, and occasionally through the infield. and often at WOT accelerating as fast as the motor will allow

 

Paul - that is not the argument . Stop you posturing and stick to what the original argument was about .

Will a lightweight flywheel change the hp as reported by a dyno ?

Answer : NO

Thankyou

 

hehe, yeah we got over that pretty quick :P

sorry for trashing your thread, but FWIW i'm done now.

Arguing this with someone who doesnt understand it is pointless and I'm not quite prepared to be banned for agressively questioning someones intelligence

 

It's sad that you are not clever enough to know what the point of the argument is ....

 

As I have clearly stated multiple times, at a fixed RPM the rotational mass makes no difference to the power measured. But unless you reach said RPM magically and instentaneously, you have whats called a curve, they are seen on plots. and more importantly they make a drastic effect of real life driving(reference 600HP supras to 1000HP Supras - they both do 10's)

What you have continued to ignore, is that what you are arguing and defending is not the ******* point of the modification!!!!
This is why no one gets into the dirt with drivetrain losses. Because there is no simple fixed number, or percentage. Most people simply cant understand the math.

Reducing roating mass does not "create" more power, not can it add to total possible power at a given RPM. But it allows FASTER ACCELERATION of the drivetrain, and this is measurable via torque - this is by defenition.

If you cannot understand that your "dyno number" is not the point of a mod like a lightweight flywheel, or driveshaft, or pistons/rotors/cranks/etc ad nauseum...

Then I retract this statement and present the idea that you Sir, are a ******* idiot

 

Without wishing to induce another outbreak of gratuitous sarcasm , has anyone out there done a before and after dyno when fitting a light weight flywheel? Surely that would answer the question by replacing theory with fact?

[I am not questioning the intelligence of either combatant here - just interested]

Edit - Paul's last post just answered my question I think - i.e. hp won't change but torque will? I will now run away.