Flywheel Advantages?

[djr81]

I spoke to a few mechanics today and the majority said the same thing to me, if I'm making the power which I am looking to get 220-230rwkw, then lightweight is generally benefitical in all areas for me, especially the street due to the acceleration advantages it brings about.

Majority also said lightweight flywheel is worthless on a bone stock car, where acceleration may be increased but in the long run the times on track will be reduced, due to the fact that the car is not producing enough to meet the minimum standards required to achieve maximum advantage of a lightweight flywheel (half decent power is required).

I don't know if it's just because they are all trying to sell one to me or not, but they said at the 220rwkw power range there are no real major drawbacks and would recommend I put one in 110% if the gearbox is coming out.

Do you agree with this???

Yes. If you are replacing it anyway & can live with the lesser flywheel effect when you are driving/launching the car then put one in.

The second paragraph has me baffled, however. The general rule of thumb is that for a less powerful car you will be using all of its power (however much that may be) more often. So the gains of a lightened flywheel will be more important (Although as I have tried to explain, ad nauseam, not significant)

If you want to confuse the mechanic you could ask him what the "minimum standard" is.

[djr81]

hahaha.....We still see things differently and it seems like my explanations are not good enough to make you agree. Fair enough, when I got time I'll hit you up with a more detailed explanation.

P.S. Some "converted" ones dont know why they converted.

Cheers,

I don't disagree with your explanation, just your conclusion.

[MR R34]

So in saying that, would you say if you were in my position you would put one on?

[djr81]

So in saying that, would you say if you were in my position you would put one on?

If you have the money, yes.

[PX29]

Well up to you, but I was trying to quantify the change & give people an idea of what sort of order of magnitude to expect. Make 5kg if you like, but you don't chuck 5kg worth of gear on your car and suddenly turn it into a slug.

The equivalent mass reduction on the car is far more than 5kg, its more like 20kg/1kg flywheel reduction.....this value is highly dependent on the gear/diff ratio as I mentioned before. Any rotating parts in an engine absorbs the energy which it produces, lowering the mass of rotating engine components allows for more of the energy to be transfered to the wheels. So if you took 5kg of the outer diameter of a flywheel, then the "Equivelant" mass reduction is in the order of 100kg (approx in 1st Gear).......These are only approx figures guys.

MR R34, Yes if I was in your position I would get it. Make sure you buy a good quality flywheel and DONT get the standard one lightened (Well unless you really really trust the machinist).

Let us know how you go mate....

Cheers.

Edited August 30, 2007 by PX29

[djr81]

The equivalent mass reduction on the car is far more than 5kg, its more like 20kg/1kg flywheel reduction.....this value is highly dependent on the gear/diff ratio as I mentioned before. Any rotating parts in an engine absorbs the energy which it produces, lowering the mass of rotating engine components allows for more of the energy to be transfered to the wheels. So if you took 5kg of the outer diameter of a flywheel, then the "Equivelant" mass reduction is in the order of 100kg (approx in 1st Gear).......These are only approx figures guys.

MR R34, Yes if I was in your position I would get it. Make sure you buy a good quality flywheel and DONT get the standard one lightened (Well unless you really really trust the machinist).

Let us know how you go mate.

Cheers.

Oh. Well I was going to get a stroker kit for my Rb26. But seeing as it will add the equivalent of about 100kg of mass to the car I guess it will just make it slower. (Joke, don't get angry)

If you really (really, really) want & you can find the flywheel dimensions (diameter, thickness) I can do the calculation to and thereby find an equivalent mass (in each gear) for some flywheel lightening.

Oh and don't forget when you change up a gear whatever energy is stored in the drivetrain is then returned to the car...

Edited August 30, 2007 by djr81

[PX29]

Oh. Well I was going to get a stroker kit for my Rb26. But seeing as it will add the equivalent of about 100kg of mass to the car I guess it will just make it slower. (Joke, don't get angry)

If you really (really, really) want & you can find the flywheel dimensions (diameter, thickness) I can do the calculation to and thereby find an equivalent mass (in each gear) for some flywheel lightening.

Ok, I just didnt want to turn this into an Eng calcs thread. Thought the explanations was enough without going into the calcs........BUT bring it ON....

Cheers.

Edited August 30, 2007 by PX29

[djr81]

Ok, I just didnt want to turn this into an Eng calcs thread. Thought the explanations was enough without going into the calcs........BUT bring it ON....

Cheers.

Well the explanation wasn't the issue. The conclusion & the equivalence was at issue.

Anyway I don't have the thickness & diameter for the RB26 flywheels, so I can't do any calcs.....

Anyone know how big they are???

[MR R34]

Yeh I'm buying the nismo lightweight flywheel that comes in the sports clutch system which supports 420ps. It's costing me an extra $400 including delivery...

[PX29]

Based on the following details, see the "Equivalent" mass decrease on car per 1kg reduction on the rim of a flywheel of diameter 30cm.

For R32 GTR

Diff Ratio: 4.111

Gear Ratios

1st: 3.215 = 22.8kg

2nd: 1.925 = 8.83kg

3rd: 1.302 = 4.58kg

4th: 1 = 3.11kg

5th: 0.752 = 2.19kg

Reverse: 3.369 = 24.98kg

These figures may sound impressive, but you have to remember that this is only valid for mass removed from the outer edge of the flywheel. I'm not sure on the geometrical size/weight of the standard & nismo flywheels. So just by finding the difference in weight between standard and aftermarket flywheels and multiplying by the above figures isnt accurate. Anyway, this shows that reduction in flywheel mass does in my opinion make a significant dercrease in "effective" total car mass in the lower gears. Far from the "1 milk bottle on the flywheel = 5 milk bottles in the car" analogy.

I guess we will find out once MR R34 gets back to us.

Can someone confirm these figures as a check.......?

cheers.

Edited August 30, 2007 by PX29

[djr81]

Yeah.

I got different numbers. MAybe you need to show how you workerd them out.

My method was.

Find gearing in km/h per 1000rpm.

Select a speed an/or a speed range (doesn't matter)

Work out how much Kinetic energy (or change in) a 1kg mass has in a llinear circumstance.

Work out its equivalent for the flywheel.

Divide one by the other.

I got slightly less than 2 for the car in fourth.

[PX29]

I dont know how to add attachments to the post, doesnt seem to work.

I basically assumed that if we have two identical cars and one had additional mass on the flywheel and the other has an addditional mass on the car which allowed both to accelerate at the same rate, then at any point in time, both cars will have the same kinetic energy. Equating kinetic energy equations for the 2 cars gives a result which relates the additional flywheel mass to the mass added on car. This shows how the flywheel mass effects the load the car experiences.

Look what you started MR R34......

Cheers.

Edited August 31, 2007 by PX29

[MR R34]

Look what you started MR R34......

Cheers.

lol, sorry mate didn't think it would turn out to be a mathematical debate. All I asked for was some opinions and whether or not it is a sure thing to put on if changing clutch, responses seem as tho it is.

My mate put one into his R33, running 11s, and says he loves it, reckons there is a real noticeable difference in 1st gear to 3rd gear, accelerating and reaching high rpm much quicker...

I'll be putting one in within the next few weeks, just depends on how long it will take to bring down. Can you guys recommend anyone that's fair priced with nismo clutches???

[djr81]

I dont know how to add attachments to the post, doesnt seem to work.

I basically assumed that if we have two identical cars and one had additional mass on the flywheel and the other has an addditional mass on the car which allowed both to accelerate at the same rate, then at any point in time, both cars will have the same kinetic energy. Equating kinetic energy equations for the 2 cars gives a result which relates the additional flywheel mass to the mass added on car. This shows how the flywheel mass effects the load the car experiences.

Look what you started MR R34......

Cheers.

Easy. Click reply (not fast reply).

Type some stuff in.

Find the browse button which turns up.

Click it, then find your jpeg file.

Click upload.

Wait for a bit.

Click add reply.

Job done

[PX29]

Ok......here's the calcs..

This is just the way I did it, I'm sure there are other ways also.

Just put in the values for flywheel mass (Mf), flywheel radius, diff ratio, gear ratio and tyre radius and the result (Mc) is the equivalent mass "on" the car for that gear ratio.

So if your flywheel has a reduced outer mass of 5kg compared to standard, then as posted before you get an overall reduction of 5x20kg = 100kgs (1st gear) - 32gtr (assuming flywheel radius 15cm, tyre radius = 30cm).

Does anyone know the flywheel diameter for r32gtr..?

Cheers,

FlywheelCalcs.pdf

[djr81]

Much easier if you use the figures for km/h per 1000rpm.

Using the same formula.

4000rpm in 4th = 114KM/H.

So

Ek (linear) = 501J/kg.

Ek (rotational) = 987J/kg based on a flywheel of 300 dia, uniform thickness.

So just less than twice as important.

Tellingly, based on a wet weight with driver of an R32 Gt-R being 1600kg, the Ek of the mass of the car (without any rotational component) is 2,550,000J. So our gain of 987J/kg is pretty inconsequential.

Also it is worth noting that you are storing energy in the flywheel, so when you change gear you get it back. It isn't lost unless you need to put your foot on the brakes.

Lastly, in 1st it is pretty irrelevent given nearly everyone stuggles with traction. For alot of people this is true of second.

[PX29]

Much easier if you use the figures for km/h per 1000rpm.

Using the same formula.

4000rpm in 4th = 114KM/H.

So

Ek (linear) = 501J/kg.

Ek (rotational) = 987J/kg based on a flywheel of 300 dia, uniform thickness.

So just less than twice as important.

Tellingly, based on a wet weight with driver of an R32 Gt-R being 1600kg, the Ek of the mass of the car (without any rotational component) is 2,550,000J. So our gain of 987J/kg is pretty inconsequential.

Also it is worth noting that you are storing energy in the flywheel, so when you change gear you get it back. It isn't lost unless you need to put your foot on the brakes.

Lastly, in 1st it is pretty irrelevent given nearly everyone stuggles with traction. For alot of people this is true of second.

I dont know what you've done there..???. Yes the extra energy is stored with heavier flywheel hence reducing energy available for acceleration. Do you still disagree that the 100kg figure is wrong or insignificant..??...

Yes more power hinders traction in first.......yet we still want more power.......so then we get wider tyres..

I agree there are many other factors to take into account, driveability, traction, etc.... its up to the individual at the end of the day. We could go into this alot further but I think thats enough.....

Edited August 31, 2007 by PX29

[T04GTR]

hahahahhahahaha this is funny.

put it on the dyno and see. you gain therortcal hp. but loose torque.

and to add to that the old saying..power sells cars torque wins races.. btw we are mayby talking .1sec around a race track. mayby....

[djr81]

I dont know what you've done there..???. Yes the extra energy is stored with heavier flywheel hence reducing energy available for acceleration. Do you still disagree that the 100kg figure is wrong or insignificant..??...

Yes more power hinders traction in first.......yet we still want more power.......so then we get wider tyres..

I agree there are many other factors to take into account, driveability, traction, etc.... its up to the individual at the end of the day. We could go into this alot further but I think thats enough.....

Well my point was that, for me, I get wheelspin (see the ragged blue line on the data log) on corner exit in third. So the lighter flywheel isn't helping here & in anycase doesn't make much of a difference in the higher gears. The 100kg is nominal & as I said is not relevant for me because in the second or so (Based on a 0 to 100km/h time of 4 seconds) the car is in first barely any of it is with traction at the wheels.

Maybe we can agree on some motherhood statements.

A heavier flywheel will store more energy than its lighter equivalent.

A lighter flywheel will make in gear acceleration slightly quicker, but only if you have traction - otherwise it is irrelevent.

The benefit of a lighter flywheel is more substantial in lower gears. The relationship is proprtional to the square of the gear ratios.

You get the stored energy from the flywheel back when you change up a gear.

A heavier flywheel makes the car easier to drive.

A lighter flywheel makes the motor more responsive when the clutch is depressed.

A heavier or a lighter flywheel MAKES ABSOLUTELY NO DIFFERENCE to the amount of torque and horsepower your car produces.

If you have the choice, the cash & can live with the slight driveability losses then get one.

Calculations are both fun & tell you things about the real world where you would otherwise have to rely on peoples opinions. As can be seen from this thread there are as many opinions as people. Given that everyone disagrees on nearly everything you have to accept that most people are wrong. The hard part is figuring out who...

Edited September 3, 2007 by djr81

[PX29]

Yes the calcs proove something, but taking into all other factors its up to the individual if they think its worth doing the mod.

I Agree with your statements there djr81.

Cheers.