flywheel

[LEV_101]

i was told by someone ( random dude ) that the lighter the flywheel the less torque you have ? is this true ?

cheers

[groupagt4]

no

[LEV_101]

then WTF was he on about .... flywheel only helps the motor rev faster. and thats it ?

[big_boy]

accually this is tru

a lighter fly wheel will give you less torque but will rev quicker & higher

a heaver fly wheel will give more torque dew to the fact as it takes more effit to stop it spinning but will also take longer to rev up & will be harder to get to spin as fast

[LEV_101]

so confused now ... who to trust ?

[big_boy]

its simple if you have a bigger spinning mass then it takes alot more effit to stop it this effit is relayed in to extra torque

when you do a motor up & put a lighter fly wheel on you gain HP by revs but loose tork altho you then make it up with the revs

say with a std 3L motor with a 12kg flywheel you have 200nm @ 3000rpm

then say the same 3L motor with a 5kg flywheel may only have 130nm @ 3000rpm

but alt the same time will rev to maby 7500rpm insted of 6500rpm its all about shifting your power to were you want it

the lighter flywheel will have more HP at say 6000rpm than the heaver tho

it just depends were you want power

[LEV_101]

its simple if you have a bigger spinning mass then it takes alot more effit to stop it this effit is relayed in to extra torque

when you do a motor up & put a lighter fly wheel on you gain HP by revs but loose tork altho you then make it up with the revs

say with a std 3L motor with a 12kg flywheel you have 200nm @ 3000rpm

then say the same 3L motor with a 5kg flywheel may only have 130nm @ 3000rpm

but alt the same time will rev to maby 7500rpm insted of 6500rpm its all about shifting your power to were you want it

the lighter flywheel will have more HP at say 6000rpm than the heaver tho

it just depends were you want power

now im more confused. people say putting a light weight flywheel will not gain power ?

[big_boy]

it wont gain you power but it gains revs witch can be turned it to power

[big_boy]

& to the fact if changeing a flywheel wont change power or torque then why change them at all to lighter ones heaver ones ect

the fact is flywheels make big differences to torque & HP

why alse dousent every car have a 5kg flywheel of the same size no matter what if it makes no differences what so ever witch is what your saying

if any one alse has another way of wording what im saying then have a try as i know im shocking at wording things

[frost]

^^yea all he has said is true i did alot of research before i got my jun 4.3 flywheel.

up hill with light weight flywheel is fun....not


ill have a go,

heavy flywheel: its all about momentum, it takes longer to spin up but when you do spin up the flywheel its got alot of push to it(torque) and all this force transfers down your drive train to the wheels keeping everything spinning harder. =less loss of torque

light weight.
it spins up fast but with no force behind it, you dont have the torque to push anything along, to get the power, you have to rev it up higher in the band to make up the torque, so instead of taking off at 1300 rpm now you have to takeoff at 3000 rpm to move the same car.

summery: heavy flywheel = the HULK
light flywheel = spiderman

in a light weight car you'll be best with the lightest flywheel you can find because there is not alot of car to move. the opposites for heavy car

[big_boy]

up hill with light weight flywheel is fun....not

thats why you need more CC

or lower gears so you can use higher revs & be in your new power band

[Punter]

The way I look at it (makes sense in my head)

Is that the flywheel can't have an effect on power or torque when the engine is at a fixed speed.

However when the engine speed is increasing, a lighter flywheel means the engine sees less load, and thus has more power.

[frost]

but the load IS the flywheel its the gyro(sp) that keeps everything spinning

[big_boy]

The way I look at it (makes sense in my head)

Is that the flywheel can't have an effect on power or torque when the engine is at a fixed speed.

consent speed & load correct but unless were talking about pump motors witch i dought this therid was made for then they do make a big difference

[Grrrrrrr!]

Lightening a flywheel does not change your power or torque at all.

Torque & power come from the combustion of Fuel/air mixture. Taking metal off the flywheel or adding more
on will not get more air/fuel into the combustion chamber.

Think about.. how do turbos work... they force more air/fuel into the cylinder..
same with big cams, head flow work etc etc.

Put a car on a dyno, take it to any point in the rev range (peak torque, peak power, whatever)
hold it there using the dyno brake and get a horsepower figure. Change flywheel put it back on the dyno,
take it to same revs, hold it there and get the horsepower figure again.
The horsepower figure will be exactly the same. (if nothing else has changed).

But wait...
If you put it on a dyno and do a dynamic run (a typical rolling road "dyno pull") where the car
is not being held at a set number of revs then a lighter flywheel will show an increase in torque and power.

Why? Because the engine is making the same amount of torque & power, but now instead of having to
accelerate a big heavy flywheel to 8000rpm it is accelerating a much lighter flywheel.
Therefore more of the engines torque is going to the wheels where the dyno is reading it. (dynos dont read power, they read torque and rpm, then calculate power)

Remember high school physics? Force = Mass x Acceleration.
So if the engine produces the same amount of force (torque) but has less mass (weight*)
to push around it will push it faster.

When you hold the engine at a set number of revs on the dyno the flywheel speed is constant,
so no force (torque) is being used to accelerate it so all the torque goes to the wheels.

Part three:
"everyone tells me when you put a lighter flywheel on you lose torque.. but you just said it doesn't change.."

Yep. That bit above where i said on a dynamic run you'll accelerate faster works the other way too.
If your engine isn't making enough torque to pull you up a hill because you are in too high gear
you dont have a big heavy flywheel to keep you going.. therefore your entire car slows down faster.
The actual torque hasn't changed, just the amount of acceleration/deceleration due to less weight (mass).

And a few more things that all relate to this:
Light flywheels make a huge difference in lower gears, and not so much in higher gears.
Why? think about how long it take to rev your car from 3000rpm to 7000rpm in first gear.. not long.
But in 5th gear it takes a lot longer.
But the change in flywheel speed is the same. So the amount of energy it takes to accelerate the
flywheel is the same. but if you take that energy off the engine at a slower rate (ie. over more time)
you are taking less energy per second from the engine.

*Weight isn't actually the whole story with flywheels.. what really matters is Mass Moment of Inertia.
A bit of a mouthful ain't it.
You could have two flywheels that weigh the same on a set of scales, but one could
be a lot "heavier" in terms of the flywheel effect. Why?
Basically because the further out from the center the weight (mass) is the faster it is moving.
The faster it has to move the more energy it takes to get it there.
So a flywheel with less weight on the outside edge will spin up easier than one with all the weight on the outside edge.

Maybe one of the Mods would like to sticky this?

[strx7]

2 words

ROTATIONAL INERTIA


It doesn't make any less torque, more torque or horsepower. It simply has more rotational inertia.

ever seen a 2 1/2 lb rotary race flywheel??? no mass to rotate but VERY VERY responsive to drive. Oh so easy to light up the rear wheel when under way.

[Punter]

but the load IS the flywheel its the gyro(sp) that keeps everything spinning

Yes the flywheel acts as a,... well, flywheel.

Fact is the heavier the flywheel is the more energy required to change it's speed.

[Punter]

The way I look at it (makes sense in my head)

Is that the flywheel can't have an effect on power or torque when the engine is at a fixed speed.

consent speed & load correct but unless were talking about pump motors witch i dought this therid was made for then they do make a big difference

You didn't read the last line of my post then

[pc]

accually this is tru
a lighter fly wheel will give you less torque but will rev quicker & higher
a heaver fly wheel will give more torque dew to the fact as it takes more effit to stop it spinning but will also take longer to rev up & will be harder to get to spin as fast

Sounds completly wrong.
Who revs to red line in the middle of a straight and then drops the clutch?... cos that's the only way you will get more torque

[Mr Revhead]

Maybe one of the Mods would like to sticky this?

very good idea

http://forums.toyspeed.org.nz/viewtopic.php?p=580478#580478


thanks guys