Does a Light Weight Flywheel give you more power?

[antnicuk]

as above really.  Why do stock cars have such heavy ones,  the series 4 Turbo one is really heavy compared to a TII or an FD which is lighter still.

Any pro\'s or cons?

[elford_tim]

A lighter flywheel will allow the engine to rev quicker as there is less mass to be accelerated when you hit the loud pedal. It may give you a little more power right at the top end but the main point is that it makes the engine a tad more responsive.

The downside is that you lose some bottom-end torque as the mass of the heavier flywheel helps to mask the lack thereof on a rotary to a certain extent.

[Jono FD3]

Heavyer flywheel results in more inershia..... smoother running at low speeds as the weight of the flywheel is forcing the engine to turn over!!

Lighter flywheels result in quicker throttel responce as there is less weight to turn on the crank.... this also results in slightly heavyer idleing as there is less weight spinning keeping rotation going between combustion strokes!!

Learnt this on my Mini!!!
Hope its answerd your question (and you can understand what I\'m trying to explain!!)
Jono

[Jit]

torque at the wheels = torque at the crank - driveline inertia

lighter flywheel= less inertia = more torque at the wheels = more power at the wheels

power = torque x rpm

[Warthog]

Ant, as above. I have run one from very early on in my modding game. It takes a bit of getting use to as you are either on power or off, so you have to change your style of driving or you feel like you have kangaroo juice in the tank. But fantastic when you want power, bang it\'s there no waiting for the revs to build up. How can I make that sound simple.
Right you have been driving along in low boost mode behind some muppet out for a sunday drive, easy to picture that it\'s happened to us all, you press high boost see your safe overtake and in 3rd she is released and flys--1. Because she is as bored as you. 2. because you have let her have more boost and she responds with lightning speed and 3. because it feels:flamed  good.
Well thats what it feels like when you drive an engine with a normal flywheel, sluggish and then drive the same engine with a lightened one it is so much more responsive -- bang power.
Hope that makes sense.

[Adriansturgess]

So it seems to be that it does not make the engine more powerful as such, but it allows quicker build up of revs so reaching into the power band more quickly and giving you quicker access to the available power.

[Warthog]

Thats what I said but you said it a lot bettttteeeerr than what I did.:Tongue1

[TRex]

Hmmm, people only seem to think it is a good thing...  incorrect information again..
 A lighter Flywheel also has a bad side like everything else...
 \'Like reduced Torque!\' :yes

[TRex]

Best explain before the boo boys start...

 It takes effort to get the \'Flywheel\' rotating and stops the engines revs increasing or slowing down quickly. A \'lighter wheel\' takes strain off the engine and allows the engine to rev more freely.  
 A race-tuned engine increases and decreases revs a lot more quickly than a standard engine.
 A result of that with a Turbo charged motor is that the revs drop off quicker so a more rapid gear shift is needed to keep the engine in the sweet spot!
 
 But the big downside to a \'Lighter flywheel\' is that torque is reduced – most noticeably on a hill. Whereas the momentum in the engine is maintained with a heavy flywheel the momentum is reduced and the hill has a much more direct effect on the engine output. Best used in a race situation where the track is flat with a demand for fast engine speed changes and the \'Engine has been tuned to output power matching the flywheel capacity\' (high revving).  

 You can\'t just throw a \'Lighter wheel\' on and think your car is faster or better, it can be worse...
  Different grades of flywheel are available for different situations.
 Various weight of flywheel are available allowing you to get the best torque/free revving capabilities.  But depends on your engine capablities and requirements which is right for you (weight)..

 :Thumbs-up

[mullins]

The lighter you go the less engine braking as well.

[Initial-D]

Also much easier to bog down when launching unless you keep the revs up, due to the reduced inersia (rotating weight).

The benefit is response.

[nikp]

A lighter or heavier flywheel is not going to change torque one way or another!! People need to get this confusion out of the equation! Most arguments are correct here, but accurately, the torque will not be effected!

It\'s like saying, if i fit bigger wheels, it will reduce the torque. The wheels (Or flywheel in this case) have no impact on the power or torque developed by the engine! A heavier flywheel will reduce the effect of the torque.

Put it another way. Most people know the formula F=ma. Force = mass times acceleration. In rotational mathmatics, Torque is the rotational equivalent to Force. Therefore, if you reduce the mass (It\'s actually \'Moment of inertia\', but lets stick with mass at the moment!) the force will remain the same, but the acceleration will increase. Hence, why people like to go for lighter flywheels: For the same engine torque, you\'re acceleration will be increased. It will depend upon how much lighter (And where the reduction of mass has taken place) the flywheel has been made.

I hope that\'s not got too technical for people!

[antnicuk]

many thanks guys,   i dont want one of those little ali things that weighs nothing, i\'m want a steel one thats a somewhere near the stock FD one or a little less.  I couldnt fit the stock FD one as the counter weight is wrong for the low compression S4 rotors i have.  Hence going for an aftermarket one.

As i said the s4 one is HUGE.  its several pounds heavier than a TII and a TII is heavier than a FD so an FD one would have been great!

[Jit]

is the TII one not the same as an FD one? Ive got a TII one which i removed from a TII and it looks identical and feels of identical weight to the one i removed from my FD

[antnicuk]

i thought that the TII was heavier but i may be wrong