lightweight flywheel makes MORE of a difference on FI cars.

http://www.euclideanspace.com/physic...city/index.htm

 

I don't know what I was thinking. Flywheel gives no HP just faster acceleration. Faster acceleration should be a good thing regardless of HP amount. I'm not sure what I was reading that skewed my thinking. MORE of a difference with FI? I'm not sure I understand that, unless you are talking about racing application. Sorry for the misleading post.

 

Is it even out yet ? ...

 

What you were reading but wasn't explained was:

Light flywheel is not needed and preferred not to have if you are FI and into 1/4 mile times.

FI gives you plenty of torque and HP.

In drag racing you need torque anyday over HP. You have plenty of HP.

Light fly = loss of torque = pulling power at high speeds.

Light fly = faster accelerating up to a point, then torque takes over.


I just installed the ACT PRO LITE w/ Centerforce clutch.


After four short drives:

My car is easier to engage into first and all the other gears.

It's hard to tell now. Seems a little quicker w/ a little less punch. Much smoother.

This Mod is hard for my butt dyno to verify.

Need to track it, before I can make better evaluation.

 

Not yet,

But the specs are insane! Easily the lightest toughest flywheel/clutch setup on the market. (and this is coming from the guy who has the 8.5 lb fidanza!)

I hesitate to mention absolute values before I can get my hands on one and witness its weight on my own scale. But this will easily be the clutch and flywheel of all clutch and flywheels for the rx8.

I'm tossing out my fidanza the second it becomes available.

 

heavy flywheels are used to store energy to make shifts easier. They can also be rev'ed up and clutch dropped in drag applications to help the car's initial torque.

But any way you slice it, having a heavy flywheel and clutch subtract power from what the engine is trying to give to the wheels. Good for 1/4 mile stretches and rock climbing (where you also have final drive ratios of 80:1), bad for any type of driving where the clutch isn't being "dropped", autox, road race, everyday driving.

 

the reason it makes more of a difference in FI cars is because as the FI system puts more and more power into the car accesories and masses have more of an effect on the total power to loss percentage.

So basically the underdrive pulley gains about 5-7 hp on a N/A car making about 190-200 hp. Because it is subtracting from the percentage of the total loss on the car. Meaning that on a car making 400 hp you would probably gain around 15-20 hp by just switching to underdrive pullies.

Or the flywheel that would gain maybe 5-10 hp on a N/A car making 190-200 hp would now gain 20-30 hp on a 400 hp car.

So the little things add up.

 

To think of why lightweight flywheels are better, just imagine that you are trying to spin a disc that weighs 45lbs.

Its going to be hard to get started, right? Its going to take some elbow grease, even to get it up to say 30rpm. Not to mention its going to be hard to stop once it gets going.

Now imagine if you were trying to spin a weight of the same size that weighs 5lbs.
It would be a lot easier to spin it up to 30rpm and keep it there, correct?

Thats what a lightweight flywheel does, on the heavy flywheel, if you grabbed it with your hand while it was spinning it would transfer a lot more energy to your hand than the light flywheel, but in order to get it up to speed again it would WAY more energy than the light flywheel.

 

i will pay for shipping if you toss it my way.. a lb is a lb...

beers

 

Really? I have Fidanza too, should I toss mine away as well ?

but I am not going to give it to swoope



-----------------

Cant do my FW and clutch today, too freaking cold outside grrrRRRRR

I was about to start it this morning, but I went outside for 15 minutes, then I turn myself back to my garage and close the door. Too cold.

God damn it ~

 

You don't gain any HP with a lighter flywheel. You use the excess energy not used to spin a lighter flywheel (as opposed to a heavier one), now as energy to accelerate or push the car along. It's a transfer of energy (HP) faster, not a gain.

 

Wouldn't the gained acceleration from the lightweight flywheel car pull on a heavier one in a drag race. I undertand the initial clutch-drop drawback, but wouldn't the extra acceleration outweight it.

 

I have a hard time seeing why people are confused as to why a lighter flywheel works... Think of it like this:

Think about trying to hold a 5lb bucket at full arms length away and lift it quickly. Then take a 2lb bucket and do the same... Feel the difference? (See awesome illustration below) Now you could have a heavier flywheel still be fast if the mass were move closer to the center point. Again, think about trying to hold a 2lb bucket at full arms length away and lift it quickly. Then take a 5lb bucket and keep it close to your chest and lift it. Even though the 5lb fbucket is heavier, it will actually require less work to lift..or take that lift into a circular rotation and poof - the flywheel that is heavier in overall weight actually requires less torque from the engine to move =>better acceleration

 

Lol I was thinking of the implications of someone who actually wanted to win at drag racing.

Funny if they actually went about it the best way to do it instead of the "established way" Ideally I would build a car with one giant wheel with the driver sitting in the center, 4 engines all driving a 1500lb single spinning wheel that encircles the drivers compartment, get it up to 30,000 rpms before the tree went green, cut the engines and watch it fly. Weight of anything wouldn't matter if you got the inertia of the giant mass up high enough

Wouldn't have to shift, the stored inertia of the mass would extract all the power from all 4 engines for the entire run.

 

I will quote myself to get back to my original question and ask it in a different way.

Car produces x amount of power...lightweight flywheel frees up a % of that power and uses it to accelerate the crankshaft faster & deploy HP faster.

1. If stock car + stock flywheel accelerates the crankshaft at x power
2. Then stock car + lightweight flywheel accelerates the crankshaft at x + some %
3. Then FI car + stock flywheel accels the crankshaft at (x w/FI) + some new %
4. Then FI car + lightwheel flywheel accels the crankshaft (x + FI) + at greatest %

1 is slowest accleration
4 is fastest acceleration

2 is still less than 3 right.

So my original question - the %'s, is anyone able to make a good guesstimate.

is going from 1 to 2...a noticeable higher percentage jump than going from 3 to 4, thus meaning a more noticeable change for a lightweight flywheel on a stock car as opposed to on an FI car.

 

with a FId car you are accelerating the flywheel faster than N/A so it is definately going to be worthwhile - whether it has more or less effect on a % bassis when compared to an NA car is a good question - and anyones guess ......

 

That may be true for a 200hp renesis but for a 400hp renesis it would be more than 2.7HP per pound - yes ?

If you double the acceleration of the flywheel you might double the effectiveness of the weight reduction ? So the question then becomes - will double the horsepower give you double the acceleration ?

Or is the effectiveness a square of the acceleration difference - brain hurting now

 

you are starting to get into a chicken and egg argument there - heh

So - in conclusion , all said and done , at the end of the day burble burble the following statement may well describe the difference

A LW flywheel on a FI'd renesis will be more effective but less noticable than one fitted to a N/A renesis .

 

I stand corrected. The word should be inertia not torque.

 

^ +1

 

^ +2

 

A little update as some of you know the ACT counterweight is the Mazda one (52x) the difference is two small holes drilled in the side as seen in this picture:





Hope that helps clear up some confusion.

 

stock one is drilled also.

Each one is cast slightly differently, so they put each one on a balancing machine and subtract weight from the location that will make the balance correct. The location of the drill holes should be different for each piece seeing as casting will not always produce the perfectly balanced piece.

They do the same thing for crankshafts or anything else

On both the rx7 and the rx8 the rotors are offset 180 degrees so rotor location isn't a factor that would explain the location difference.

For example, mine is drilled with 2 holes more toward the center of the indentation.

whats the weight difference?

 

Hmmm I guess we'll have to wait for NYGPS to do some weighing with the same scale... and compare the two side by side.

 

The scale @ my father's place only measures in whole pound.

Im going to buy a scale soon just for this purpose. Looking at some really accurate one with up to 3 digit after the decimals .