Lightening a stock flywheel

[mullins]

A little birdie told me Tweatit actually source some of their parts from SimplyMaz and then just throw on a mark-up.

Try Shan at SimplyMaz before you buy anything from Tweakit!!!

[Trevrx]

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=005&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=150055899384&rd=1,1

That seems like a good deal ^.

Sorry to be dumb, but why does the flywheel need a counterweight at all?
How do you work out where to fit it? If it fits to a pre-marked posistion, why don\'t they supply it with the weight attached?  Anyone....?

[Martiny]

Ok. Well, our shaft is not straight for a start, it has 2 eccentric lobes on it. So these lobes are going to create centrifugal force as it spins at 8 k rpm. So we have some weight added to the flywheel on one end of the shaft, and then we have a weight on the other end of the shaft. This weight is inside the front engine cover. The whole assembly is designed to smooth out everything so we have minimal vibration.

[Martiny]

Now, I have a question.

Why would anyone want to lighten the flywheel?

[Martiny]

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=005&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=150055899384&rd=1,1

That seems like a good deal ^.

Sorry to be dumb, but why does the flywheel need a counterweight at all?
How do you work out where to fit it? If it fits to a pre-marked posistion, why don\'t they supply it with the weight attached?  Anyone....?

There is another reason, apart from vibration. If the whole shaft, rotors, flywheel and counter weight are not balanced within spec, then the bearings will wear much faster.

[Trevrx]

Thanks Martiny.

So back to your question, why lighten the flywheel at all? I guess there must be a benefit?

Howcome the standard counterweight part fits all lightened flywheels even though the choice of flywheels available are different weights?

[kev-yorks]

To clear this up you DON\'T need a light counterweight for a light flywheel. You use the auto counterweight because it has the mounting points already drilled/tapped into it that the flex plate normally bolts onto. These are used to locate the flywheel.
 The counterweights counter balance the weight of the rotors. If you fit light rotors then you lighten the counterweight. The flywheel is balanced in its own right and the reason people fit light weight flywheels is because there is less weight and therefore less inertia to overcome the engine will rev easier/quicker. The down side of this is the car is also easier to stall tick over may be slightly lumpier because the inertia in the engine is decreased. Another missconception is that a light flywheel gives you more power, while it only lets you get the revs up quicker which does make you faster but not with any more power.
Hope this helps.
Regards Kevin

[TRex]

^ :Thumbs-up

[Trevrx]

Thanks for that Kev, it makes sense.

But, my only question now is, the total weight of the lightened flywheel and counter weight is less than the stock flywheel, so how does that balance the rotors to the same degree as stock?

[Martiny]

Trev, just read Kevin\'s post carefully, he does say that you need to lighten the counterweight, if you lighten the Rotors.

Therefore the Auto and the Manual counter weight weigh the same.

I know exactly why lightening the flywheel helps an out and out racing or drag car. The question was actually aimed at nicsterrx7.

On a car that will see road use as well, its not a good mod to have.

[kev-yorks]

Thanks for that Kev, it makes sense.
 
But, my only question now is, the total weight of the lightened flywheel and counter weight is less than the stock flywheel, so how does that balance the rotors to the same degree as stock?

Total weight is immaterial the counter weights only are used to balance the engine the flywheel is added later purely as a means of getting drive through the clutch and adding weight to give the engine inertia. In a auto motor there is no flywheel what so ever just a thin flex plate that bolts onto the counter weight that weighs less than a kilo. http://www.mazdarotaryclub.com/forums/showthread.php?t=31765&highlight=balancing
If you scroll down to grizzly\'s pic in this one you\'ll see a rotating mass being balanced. Note only the counterweights in place no flywheel.
Kevin:WaveBye

[nicksterrx7]

Guys, thanks for the comments and Martiny, a good question why have a lightened flywheel.  I want the quicker response and greater acceleration, however I want a car that is driveable and practical more.

I have been mulling over the prospect of a lightened flywheel but have read a number of threads that suggest that lumpy running and erratic tick over could be the result.  I don\'t want this and as such am likely to steer away from this mod.