Flywheel

[Cheng]

I've been wanting to get a Flywheel ever since i got that sr swap in my sexy 90 240sx.  I been doing some research on the flywheel and everything.  I heard that if  you got to light of a flywheel it would be off center whatever that means but what do you guys think of a JUN ultra light Flywheel or just the JUN light Flywheel
thanks
Jason

[mrdirty]

The only way a flywheel could be "off center" or unbalanced is if it was not manufactured properly. Balance has nothing to do w/ weight.

A good shop will statically balance a rotating part,
a great shop will dynamically balance, so check this out.

the only disadvantages to a lighter (not weaker) flywheel that I can see is:

-need to upshift quicker to accomodate accelerated rpm drop durring no throttle.
-potential to stall at low rpm (flywheel adds a margin for error)
-slightly rougher idle.

the deal w/ a flywheel is that it adds rotating mass to the engine, which smooths everything out a bit; probably not noticable though...

[FSPtwo4d]

the light flywheel will still let you get good launches, however the extra light one will yield more hp but you won't be able to launch worth crap.

late

[whateverjames]

i know what you're talking about. i've heard if you get to light of a flywheel (somehow) it would throw off the balance of the engine. i have the regular JUN lightweight flywheel and of course, the engine is fine, but i don't know of anyone with the ultra line flywheel. :confused:

[tnord]

i think that's a myth james, like the other dude said, i don't see how simply a reduction in weight messes with the balance.

[gschroeder78]

I haven't heard that either but it sounds like it evolved from an aluminum pulley debate.

[ca18guy]

Originally posted by gschroeder78
I haven't heard that either but it sounds like it evolved from an aluminum pulley debate.

Thats what I was thinking. Not really a fair comparison though, stock pulleys have dampeners/balancers while aftermarket pulleys ussually don't supposedly causing unbalance. I don't see how that ever applied to the flywheel though, which is basically the same but lighter. Like tnord said, its a myth probably.

[kandyflip445]

Have you looked at the TODA flywheel?

[mrdirty]

I'm rethinking my opinion here:
if the whole rotating system is unbalanced then adding a heavy balanced flywheel to it will reduce the sensation of off center rotation because it will bring the center of mass of the system as a whole closer to the axis of rotation...

unfortunatelly, a heavy well balanced flywheel may reduce the FEEL of an unbalanced system but cannot reduce the actual additional loads on the system as a result of the unbalanced mass.

the only other thing that could be effected is the harmonics of the system but I don't know too much about harmonics.

[drift freaq]

Have you looked at the TODA flywheel?



My friend has it on his SR its to light. He lost torque because of it . Its a 9 lb flywheel.If you use your car for any street driving,
then you want to get your flywheel weight somewhere in between stock and the ultralight flywheels.

For SR's the Nismo flywheel is a good choice. For KA's the simplest thing to do is what I did on my old car. I took a truck flywheel (240mm clutch surface vs stock 225mm) had it lightened to 16lb's. it made a hell of a difference in engine performance and response. I did not lose my torque either which I feel you would with the Fidanza. IMHO

If you track your car only get the lightest flywheel.On the track its all about keeping the car up in the revs. i.e. mid range and top end power . Bottom end power is not as important.

[bbp]

Investigate getting your stock one lightened. I have heard of people taking up to 10-12 pounds out of a stock one. If you go to light, the car will become undrivable. It will tend when trying to move in 1st gear.

They do make a difference in how quickly the motor will rev. It will spool up much quicker.

[tnord]

i got my stock one lightened and balanced for $150, they said they could only take off 6lbs because of safety issues. so, take that for what it's worth.

[Cheng]

Im thinking more of the jun light fly wheel and ultra light flywheel the light one weighs around 10-11 pounds and the ultra one weighs from 8-9 i believe. i heard the light is more gears towards daily driving

[kandyflip445]

Originally posted by drift freaq
My friend has it on his SR its to light. He lost torque because of it . Its a 9 lb flywheel.If you use your car for any street driving,
then you want to get your flywheel weight somewhere in between stock and the ultralight flywheels.

For SR's the Nismo flywheel is a good choice. For KA's the simplest thing to do is what I did on my old car. I took a truck flywheel (240mm clutch surface vs stock 225mm) had it lightened to 16lb's. it made a hell of a difference in engine performance and response. I did not lose my torque either which I feel you would with the Fidanza. IMHO

If you track your car only get the lightest flywheel.On the track its all about keeping the car up in the revs. i.e. mid range and top end power . Bottom end power is not as important.

From what he said get the light one...

[C-Kwik]

Originally posted by mrdirty
Balance has nothing to do w/ weight.



Balance has plenty to do with weight. Even billet metals do not have perfect consistency. Shaving any significant amount of weight can throw it off balance. Easily fixed by having it balanced. Ever notice the holes on the outer edge of a flywheel? Those are areas where metal was removed to balance the flywheel. For practical purposes, generally, just resurfacing a flywheel will have very little effect since such a small amount of metal is removed.

[AKADriver]

Originally posted by tnord
i got my stock one lightened and balanced for $150, they said they could only take off 6lbs because of safety issues. so, take that for what it's worth.

Very good point. If a stock flywheel is excessively lightened, especially if it's not properly balanced, it can come apart violently on a hard launch sending shards of flywheel THROUGH the bellhousing... potentially injuring or killing someone. :eek:

[mrdirty]

Originally posted by C-Kwik
Balance has plenty to do with weight. Even billet metals do not have perfect consistency. Shaving any significant amount of weight can throw it off balance. Easily fixed by having it balanced. Ever notice the holes on the outer edge of a flywheel? Those are areas where metal was removed to balance the flywheel. For practical purposes, generally, just resurfacing a flywheel will have very little effect since such a small amount of metal is removed.

Any idea what the average fluxuation in mass/volume for even commercial grade steel is? Really friggin' low, changes in mass/volume are a result of dendrite formation and non-homogeneous alloys....conditions tightly controlled by mills. The slight fluxuation in mass is not even comparable to inaccuracies in manufacturing.

Are you trying to tell me that a 16 lb flywheel is better balanced then a 2 lb flywheel? If so, you need to go back to physics class...

BTW: It's common sense to read a post before running off at the keyboard and looking like a jackass, I already stated that dynamic balancing is critical...

BTW II: I know billet sounds like a fancy word but ALL metals are billet out of a shop, and a cnc'd part is ALWAYS of lesser quality then a equal spec forged part due to grain flow.

that was kind of abrasive, but u made me type all this crap out...

[C-Kwik]

Originally posted by mrdirty
Any idea what the average fluxuation in mass/volume for even commercial grade steel is? Really friggin' low, changes in mass/volume are a result of dendrite formation and non-homogeneous alloys....conditions tightly controlled by mills. The slight fluxuation in mass is not even comparable to inaccuracies in manufacturing.

Are you trying to tell me that a 16 lb flywheel is better balanced then a 2 lb flywheel? If so, you need to go back to physics class...

BTW: It's common sense to read a post before running off at the keyboard and looking like a jackass, I already stated that dynamic balancing is critical...

BTW II: I know billet sounds like a fancy word but ALL metals are billet out of a shop, and a cnc'd part is ALWAYS of lesser quality then a equal spec forged part due to grain flow.

that was kind of abrasive, but u made me type all this crap out...

True, but consistency is still an issue. And any inconsitencies, including manufacturing inaccuracies contribute to an imbalance of weight. Therefore, your original statement is still flawed. I didn't argue with you against the statement about what the better balancing method is. I stuck to the one issue that stood out as an incorrect statement.

If you say a 2 lb flywheel is always better balanced than a 16 lb flywheel, I suggest YOU go back to a physics class. A better balanced flywheel is just simply that...a better balanced flywheel. A heavier rotating mass creates the potential for more load around the center point of rotation, but if balanced the same as a lighter flywheel, it will not create any more thrust load than the lighter mass.

[mrdirty]

Originally posted by C-Kwik
...Therefore, your original statement is still flawed.... I stuck to the one issue that stood out as an incorrect statement.

If you say a 2 lb flywheel is always better balanced than a 16 lb flywheel, I suggest YOU go back to a physics class. A better balanced flywheel is just simply that...a better balanced flywheel. A heavier rotating mass creates the potential for more load around the center point of rotation, but if balanced the same as a lighter flywheel, it will not create any more thrust load than the lighter mass.

:rolleyes:

I'm not going to have a pissing contest w/ you so make a point or move on.

1)What exactly IS your point? What issue? For the final time, I told him that WEIGHT has nothing to do w/ BALANCE which is absolutely true, balance is weight DISTRIBUTION.

2)READ MY POST. I never said that a 2lb flywheel is ALWAYS better balanced. Once again, total mass has nothing to w/ balance; the original concern was that if he went to a liighter flywheel there would be a loss of balance, the correct answer (as I've stated) is NO, no matter how light after dynamic balancing (as I've stated) balanced is balanced.

3)You seem to be back pedaling pretty fast, first mass matters now it doesn't; I've already stated in TWO posts about balancing I think you can quit comming off as though this is some briliant idea on your part...

4) Ummm.....4 years of physics is enough for me.

I've really had enough so like I said argue to yourself; I mean seriously, you haven't added one new thought to this post....
a.k.a: post whore.

[C-Kwik]

Originally posted by mrdirty
:rolleyes:

I'm not going to have a pissing contest w/ you so make a point or move on.

1)What exactly IS your point? What issue? For the final time, I told him that WEIGHT has nothing to do w/ BALANCE which is absolutely true, balance is weight DISTRIBUTION.

2)READ MY POST. I never said that a 2lb flywheel is ALWAYS better balanced. Once again, total mass has nothing to w/ balance; the original concern was that if he went to a liighter flywheel there would be a loss of balance, the correct answer (as I've stated) is NO, no matter how light after dynamic balancing (as I've stated) balanced is balanced.

3)You seem to be back pedaling pretty fast, first mass matters now it doesn't; I've already stated in TWO posts about balancing I think you can quit comming off as though this is some briliant idea on your part...

4) Ummm.....4 years of physics is enough for me.

I've really had enough so like I said argue to yourself; I mean seriously, you haven't added one new thought to this post....
a.k.a: post whore.

1) Sounds like an issue of semantics then. We were both talking about different things. I was not referring to overall weight. I spoke of inconsistencies in relation to weight distribution and that lightening a flywheel could bring up balance issues. So in that sense, weight has everything to do with balance. I don't assume that a flywheel is balanced just because it is lightened.

2) I never said a 16 pound flywheel was more balanced than a 2 pound flywheel in the first place...it appeared you inferred otherwise.

3) Who is backpedaling? Again, I never disagreed with you about the balancing methods. Looking back, your statement is quite ambiguous. I had a different interpretation.

[mrdirty]

I give up; Ok fine the DETAILS of balancing (for anyone who still cares):

Radial force= mass x rotational velocity squared x perpendicular distance to axis of rotation. Rotational velocity is constant throughout the body so it can be removed from the equation.

Dynamic balance: Summation of radial forces resulting in zero, in other words all centripedally induced forces cancel out meaning zero radial loads.

Therefore, no matter what the weight or shape of a rotating body as long as the vector summation of the product of mass and radial distance for each particle cancels out the part is balanced; IOTW if the centroid is thru the axis of rotation then it's balanced.

Therefore when buying a flywheel or any other rotating part balance will have nothing to do w/ overall weight.

Anyother factors leading to initial imbalance after dynamic balancing are moot, including deviations in mass/volume.

Nobody wants to fight here (well most of us); we're all here to share information but when you go out of your way to discount someone's opinion make sure you're right; and if you plan on passing judgement on the clarity of others better make sure you're clear yourself which you weren't.

There is a reason flywheels are not 7 lb out of the factory (I'm sure Nissan would love to save the mat'l cost) and I'm not going to go through it again; but needless to say balance is not everything...

jim.