Flywheel Advantages?

[MR R34]

Hey,

Just want to know, what are peoples thoughts on the advantages of a flywheel? Do you guys believe there are any power gains to be made on a dyno? From what I've read there is no dyno difference however on the street, it is like having 101lbs less weight on the street???

Cheers...

[(B1) MR_fanny]

im happy with my flywheel. dyno figures dont bother me, more the way the car drives and feels. free-er revs and its noticably torquier midrange for me.

[MR R34]

Yeh, is it worth getting one on a car making 230rwkw???

[R31Nismoid]

If your replacing the clutch ye, if not... not really worth the cost of taking the box out to fit it.

[Proximity Motorsport]

also depends what you want the car for. Some like the lightweight one that will rev good... but it does lose some power from revving so easily as there is no momentum behind the flywheel, if you have a dogbox or a very heavy clutch might also be better to get a chromolly flywheel that is heavier for the added strengh

ALSO... if you are replacing the clutch too might be best to get a flywheel clutch combo cause different compound clutches n flywheels will make it slip or chatter. Big writeup a few issues ago in HPI

Edited August 16, 2007 by choku_dori

[MR R34]

Yeh, i gotta replace the clutch now its slipping a fair bit. I'm looking at getting the nismo sports clutch kit, and the flywheel works out to be $350 extra. I heard the other way around, that because the flywheel is lighter, makes it easier for the power to be transmitted through the drivetrain and to the rear wheels, in the end leading to better power to weight ratios. On the dyno figures would be minimal but on the street was told acceleration changes significantly??? Is this true?

[(B1) MR_fanny]

i believe it has to be a balanced combo. going too light will compromise on certain things. i got the 6kg instead of the superlight 4.5kg cause i still wanted to keep some enertia.

[mattymagoo22]

a big rock takes longer to gain speed when rolling, but harder to stop once rolling than a smaller rock.

rough example. When a car is in 1st gear engine sees maybe 200kg in 2nd 500kg 3rd900 and so on. If you can remove weight before the gearbox and diff (torque multiplers) you engine sees less weight and can accelerate faster for the same power.

So you won't gain power on a dyno but you will gain response on the road.

[MR R34]

Yeh that's what I thought, are they worth the money tho if car is not dedicated to all out power???

[guesty]

You will find that it will rev faster and will be great for the street / track/ and drags, butyou loose torque because it's lighter and doesn't have the momentum to keep spinning which is what you want then drifting and rallying.

[sl33py]

I lightened mine when getting a new clutch. I believe this is how it works, tell me if I'm wrong. While you don't get any extra power, if you have 230rwkw (and let's say that's 280atf), then with a lightened flywheel, you'll still have 280atf, but you might have 234-235kw actually reaching the tyres because less energy is lost in the drivetrain. When I got mine installed, I accidentally redlined it in second the first time I planted from a dead holt to 100kph, cos I was used to changing by feel and timing, but because the engine went through the rev range quickly, she bounced lol. I like the feel of it, in fact so much that I'm interested in lightening other parts of the drivetrain to get more of the power I'm already making to the ground. Seems like a relatively cheap way to maximise use of the powr you're making and I plan to go nuts later RE power, so I will want to do it sooner or later.

[mattymagoo22]

no power gains as such but the less weight your engine has to turn eg flywheel and clutch assembly, gearbox, tail shaft, diff, wheels the quicker it can accelerate.

Remember gran turismo you could get a racing flywheel and carbon fibre tail shaft and you drop .3-.4 off your 1/4 mile time on a stock s13 or similar!

[djr81]

no power gains as such but the less weight your engine has to turn eg flywheel and clutch assembly, gearbox, tail shaft, diff, wheels the quicker it can accelerate.

Remember gran turismo you could get a racing flywheel and carbon fibre tail shaft and you drop .3-.4 off your 1/4 mile time on a stock s13 or similar!

Well if it is in gran tourismo it must be true.

In reality a kilo or so in amongst 1500kg of car is undetectable. In no way is a lightened flywheel either a significant gain (as some would have you believe) or a loss (As other argue).

The only time you will ever motice it is when the clutch is in. The reduction in inertia allows the motor to pick up and/or drop revs more quickly. You may also notice the lesser amount of inertia when you drop the clutch.

Edited August 24, 2007 by djr81

[MR R34]

yeh pretty sure ill get one for an extra few $$$, replies are great thanks guys...

Edited August 24, 2007 by MR R34

[sl33py]

In reality a kilo or so in amongst 1500kg of car is undetectable. In no way is a lightened flywheel either a significant gain (as some would have you believe) or a loss (As other argue).

The only time you will ever motice it is when the clutch is in. The reduction in inertia allows the motor to pick up and/or drop revs more quickly. You may also notice the lesser amount of inertia when you drop the clutch.

Yes, it's more noticeable in neutral and just free revving it, but I've got a buttload of sound deadening and a big sub box, and I could PLAINLY tell the difference during normal driving. I could accelerate faster - It was night and day, hence why I redlined well before I was expecting to (after having driven the car in the same configuration for 2 years, I had a good feel for when I had to change, and I usually change about 2k BEFORE redline. That's gotta say something! And because of my sound deadening, I'm sure it's not having as big effect as it does on a car that's been lightened in other ways!

I would agree with others though, it's not worth doing unless the clutch is being opened up anyway, otherwise there are definitely cheaper ways to (initially) go faster.

[djr81]

Yes, it's more noticeable in neutral and just free revving it, but I've got a buttload of sound deadening and a big sub box, and I could PLAINLY tell the difference during normal driving. I could accelerate faster - It was night and day, hence why I redlined well before I was expecting to (after having driven the car in the same configuration for 2 years, I had a good feel for when I had to change, and I usually change about 2k BEFORE redline. That's gotta say something! And because of my sound deadening, I'm sure it's not having as big effect as it does on a car that's been lightened in other ways!

I would agree with others though, it's not worth doing unless the clutch is being opened up anyway, otherwise there are definitely cheaper ways to (initially) go faster.

Well, not to be rude, but I am sure you couldn't. Plainly or otherwise. The difference in hp or weight you need to be able to detect a change is quite marked & most people only think they can feel something simply because they already know it is there. In any case you get used to changes that quickly it is not funny.

[PX29]

The difference in rotational mass compared to static mass is substantial. Taking 2 kg off the flywheel makes far more of a difference than taking 2 kg of the car body for acceleration purposes.

Be prepared for decreaced fuel economy, not that this really maters on a performance car.

This goes for drive shafts and tyre/rims. You will definitley feel the difference with heavier rims..!!

I'd change to lighter flywheel if I had my g/box out.

Cheers,

Edited August 27, 2007 by PX29

[djr81]

The difference in rotational mass compared to static mass is substantial. Taking 2 kg off the flywheel makes far more of a difference than taking 2 kg of the car body for acceleration purposes.

Be prepared for decreaced fuel economy, not that this really maters on a performance car.

This goes for drive shafts and tyre/rims. You will definitley feel the difference with heavier rims..!!

I'd change to lighter flywheel if I had my g/box out.

Cheers,

Well I can't be arsed doing the calculation, but please feel free to do it for the rest of us. In a linear state kinetic energy is equal to half the mass times the square of the velocity.

In a rotational circumstance the equation is similar, but obviously uses the polar moment of inertia instead of the mass & the velocity is measured in radians per second rather than meters per second.

Whilst removing the weight from the flywheel is more effective than just removing sound deadener or whatever it is still not significant. You will find it is << 1% of the total energy which is basically undetectable unless you are either psychic or have a shed load of data logging & alot of time on your hands.

Edited August 27, 2007 by djr81

[MR R34]

I have to change my clutch so the boc is coming out that's why I thought i'd ask on ppls views on whether or not it is worth it....... To me seems as though if the box is coming out it is worth my while and money!!!

[PX29]

Well I can't be arsed doing the calculation, but please feel free to do it for the rest of us. In a linear state kinetic energy is equal to half the mass times the square of the velocity.

In a rotational circumstance the equation is similar, but obviously uses the polar moment of inertia instead of the mass & the velocity is measured in radians per second rather than meters per second.

Whilst removing the weight from the flywheel is more effective than just removing sound deadener or whatever it is still not significant. You will find it is << 1% of the total energy which is basically undetectable unless you are either psychic or have a shed load of data logging & alot of time on your hands.

Mate, comparing the effectiveness of a lightened flywheel is far more complicated than the equations you have pointed out. There are many factors such as gear/diff ratio which amplify the load reduction on the engine during acceleration. Highest improvements in acceleration is in the lower gears and less effective within the higher ones. Depending on the engine, g/box, diff etc, you can reduce the effective weight of your car significantly (in first-second gear). Without going into the details which requires some serious calcs, let me assure you that you will definitely notice the difference of a lightweight flywheel.

Mind you it does have draw-backs.

Cheers,

Edited August 27, 2007 by PX29