Seeing as Paul has been reduced to name calling and does not even know what the f'n argument is about I'll answer this for you instead .

Yes - I have done a before and after dyno

answer : it makes NO difference to the numbers as reported by the dyno .

i will keep this in mind next time we do a light wheel fly upgrade on a rx8 and post up results, only in hp or kw at the wheels, no more flywheel power figures from me. ever. lol

All that would do is dumb people down. I can guarantee you that it will produce NO change in peak numbers, and the change in the curve is possibly not even noticable. Because a dyno measures TQ@RPM in static incriments, to produce your curve.

The point of this mindlessness is that the point of a flywheel isnt to enlarge your testicles via some inflated dyno number.
The fact of the matter is, take 2 identical cars and remove 30 pounds from the rotating mass of one(and add that 30 to the body to keep total mass equal). The car with less rotational weight is ALWAYS going to accelerate faster.

Its physics. Plain and (not so)simple. Most people cant do the math behind it, so if someone cant get it in principle, well I dont know what to tell them other than to take a 1st year physics course.

go count how many times i tried to tell you that the dyno doesnt matter. the dyno CAN NOT measure this, at least in an accurate way. Your saying it doesnt make a difference to the dyno, so am I. What i am telling you is that the dyno is not an accurate/quantifiable measurement of whats changed. You have been such a bonehead that you've ignored this and been intent on arguing a point that is entirely null and void. The ONLY basis for your argument is being a dyno queen.

Great - you get it .
Now go back and reread the whole f'n argument and realise you didn't get what it was about in the first place .

This was Charles's statement that started all this BS . Can you now see why it is wrong ?

This did make me laugh . Welcome to the forums .

i got it from the beggining. what you dont get is that your concern with the change in dyno results after changing rotational mass is about as fucking stupid as expecting a glass of water to weigh more because you froze it.

stop being arrogant and think about it.... you think dozens of thousand of dollars are spent on lightweight internals for race engines for no reason? By your reasoning they could save a fuck-ton of money and simply reduce static weight off the frame instead. Right?

They do it becasue it can significantly change the behaviour of an engine, to include how fast it accelerates... all without making anymore power, OR delivering more power to the wheels at any given instentaneous point in time. Thats what you dont get Brettus. Dyno's measure based on a bunch of instentaneous readings and plot them to form a curve, and give you your precious F&F numbers. In the real world there is MUCH more to it than that. And it is because of drivetrain loss due to rotational mass

LOL Welcome to the forums :D:

did you not read the 2 or 3 times i have ALREADY pointed this out???

It doesnt make you any more right. Your still arguing that the color blue smells like wood. Sounds stupid when you try to quantify something by a means in which it is not measurable.

Again reference the multimillion dollar cars that go to extreme engineering and financial pains to reduce a few grams from a piston rather than taking 5 seconds of a grinder to some static piece of frame.

The whole point isnt to argue that your wrong, its to argue that the way you're trying to measure and thus compare any performance change from a LW flywheel is simply wrong. You've displayed a lack of understanding of basic physics principles by ever trying to aruge anything about a dyno in the first place.

My first post was merely correcting what Charles said . The drivetrain loss with a normal flywheel is 40 whp the drivetrain loss with a light flywheel is STILL 40hp . Any dyno will show that . That is my ONLY point here . I never said anything else about it . You made the f'n stupid assumption that I thought a flywheel made no difference . WRONG


repeat as per my answer above


repeat answer above again

oh?

try again, ^^^this was before i ever posted... to which i replied:

at which point it gets carried away into nonsene. rotational mass IS a drivetrain loss, but you are correct in that it cannot(at least accurately) be quantified on a dyno

this got drug into the dyno nonsense because of this:
which was an attempt to make the light go off in your head and catch on that even though the dyno may not show it, in the real world its a MUCH more significant loss than to attach the same weight to your hood, and that it is a drivetrain loss. Which you obviously didnt get....

i was not arguing whatever you must have though... I am simply telling you that your understanding of drivetrain losses is flawed. In an attempt to explain how and why, it got drug through the mud and almost tangented into other things, simply because you dont understand what drivetrain loss is and the reason that you cant effectively measure it on a dyno

so.. you remove some random amount of weight in whatever parts of your drivetrain you choose. dyno, and see no change. by that alone you are saying there is no change drivetrain loss.

then explain why the only change was in the rotational weight of the drivetrain, yet the car is suddenly much faster than if you had removed the same amount of weight from your trunk? because you reduced the loss in your drivetrain

this is why high dollar light weight internals exist. anything professional is regulated for weight and power. so there would be no point in spending HUGE money to reduce rotating weight when they could simply cut static weight and still weigh in the same. or alter an intake runner to make more power. the difference is there is a reduction is drivetrain loss that cannot be quantified by a dyno, that relates directly to a faster car. its a drivetrain loss that is much more significant than loosing static weight

OK - so this whole stupid argument started because I didn't DEFINE driveline losses .

LOL

I was looking at it in the context of Charles's post which would translate

a 200fwhp car has 40 hp drivetrain losses so 160whp
a 200fwhp car with a lightwqeight flywheel has 25hp drivetrain losses so 175whp

This is obviously wrong - hence my first post .

This is the ONLY point i was trying to make .....

i know what your point in the post was..

well, i did ask you to and although you didnt directly, you made it clear that you didnt understand what it is. I certainly hope you understand the performance difference in removing 10lbs of frame vs 10lbs of flywheel or driveshaft. But you flat out showed a lack of understanding when you began babbling about frictional losses and whatnot.


and yes, it is "lol" but its also not. the forum is absolutely FULL of nonsense like that. it wasnt the topic, or in context i know, but i can tell you from experience that new kids come in here and see that kind of thing. even though it isnt the topic or point, stuff like that stands out and they take away a misunderstanding of whats going on and how things work. which simply promotes more stupidity

and hey, sorry for being a dick about it. i had a point to make, and a valid one. perhaps i'm just not the best informative/persuasive speaker. and i've just REALLY lost any patience and tolerance for this forum lately

As far as I can tell, paul is correct in this debate.

While not a direct example/explanation of the idea, I think this kind of relates to what paul is making a point of... A dyno is typically measuring power under acceleration. It might not make a difference assuming it's at a single rpm, but with the typical dyno plot, the car is accelerating. Under WOT at any point in the graph, the car will make more power than just holding a constant rpm, correct?

lol... I'm with Paul... in the real world, acceleration is more important than total power when all things are equal. If you want a dyno queen, then no one cares, and dyno your heart away, but it's sad that you didn't realize that the dyno numbers would be the same before you even purchased the part. Now, if you actually plan on racing your car, all things being equal, you wont beat a guy with lower rotational mass. He'll accelerate away from you, and reach his peak speed faster. He'll have the advantage on you at the exit of every corner, or at a launch.

Flywheels are racing parts, not performance parts.

Lets get back to what you think I don't understand .


Flywheel horsepower is 220

Wheel horsepower is 180

What is a the driveline loss ?

Is it 40hp ?

Is loss due to rotational acceleration included in the 40hp ?

um AFAIK no one here purchased a part, that is not how this discussion started

this was entirely and totally initiated over an error referring to rotational mass not being a drivetrain loss. it actually started as semantics.

no it is not. a dyno cannot measure loss due to angular acceleration.

take that example^^ remove 50 pounds from the drive line(rotational)
Now take it again, this time remove 50 pounds from the frame(static)

both will dyno the same, the one where you removed rotational weight will be significantly faster. THAT is the point. as reddozen said, the car that removed the 50 pounds of rotational weight not only has the HP/Wt ratio change as the other, it will also make its way through the powerband faster... its a loss, in the drivetrain, that a dyno cannot measure

you cant claim you made more power, and you reduced the same amount of weight in both cases. but one is a static weight loss, the other is a drivetrain loss, and it makes a difference

I totally agree . But saying you are "with Paul " tells me you didn't understand what the point of the argument was .

ok... Brettus and I are on the same page now(I think/hope) so let me make this clear, this is what the bitching was about:


1) Removing rotational mass from the drivetrain reduces drivetrain loss.
2) Drivetrain loss cannot be measured accurately on a dyno.
3)Take 2 identical test vehicles remove the same weight from each, one from frame, one from driveline.
a)They both still dyno the same.
b)They both still have the same power to weight ratio.
c)The one with weight removed from the driveline will be faster every single time.
*Rotational mass in the driveline causes drivetrain loss, just not the kind you can measure on a dyno

That is YOUR point - with which at no stage have I disagreed .

Now lets get to MY point :

Tell me : what is the industry standard measure for drivetran loss ?

You know - the one that all manufactures and dyno operators alike use .

Is it the 40hp figure from the example above or is there some other number I don't know about ?

manufacturers? seems to me the industry standard is flywheel horsepower, such as our quoted 232HP from Mazda.....

dyno operators? the dyno spits out a "calculated/estimated" Flywheel horsepower number based on some sketchy logic at best. shit the OP of this thread ought to be a good example of that

you CAN NOT properly measure drivetrain losses on a dyno. Frictional losses alone you can, but not drivetrain loss which includes loss due to rotational mass and its distance from axis.

This almost interconnects with some other folks bitches about dyno's and the retarded obsession with them.. a dyno can provide you with some useless numbers. they are ONLY usefull if you know how those numbers are applied in relation to time when actually driving.

what good is a motor that makes (insert favorite target HP # here), if it takes 15 seconds to move from idle to 2,500 rpms? and another 2 minutes to reach 9,000rpms? A dyno CAN NOT show you that, it simply shows you that you made 700 million HP ignoring the fact that your motor takes 37 days to reach peak HP.. the numbers are utterly useless unless you know HOW and WHEN they are applied. Rotational mass is a drivetrain loss but it is not an instentaneous loss, it is a loss in relation to TIME. and IMO anyone with performance or racing in mind, should be pretty interested in TIME

I appreciate the summary and I think I've followed this debate properly but can I just clarify one thing?

When you say "dyno the same" are you only referring to hp or torque as well? That hp won't change is a nail well driven home (and then some :uhh:). But if the car accelerates faster, won't the dyno torque numbers improve with a lightened flywheel? Or am I missing something?

They can change if you dump the clutch...... but then those on one side of the debate throw away the numbers as "false torque" because it spikes then goes lower. The others argue it proves there is a benefit... and on and on it goes :P
This has been debated to hell and back ont he LS1 forums since they existed lol.