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[Omega6pot]

Hi, was thinking of putting a lightened courtenay flywheel into my 3l omega, guy from courtenay was sayin due to the lightened one not being a DMF it can cause a slight rattle at idle, if i thought it made as good a difference as it did to my v6 vectra id probably still go ahead with it, Any experience from guys would be helpful

Cheers Al

[albitz]

Dont see the point tbh,all it can do imo is allow the engine to rev up quicker when the transmission is in neutral. :-/

[mic_k]

ask Exec - he did that to his omega

[Omega6pot]

Cheers I will do mate,  at Albs the reason I want it is because if it revs freely in neutral it will also rev a lot quicker up the road, the improvement it made to my vectra was unreal, cuts the weight to a third

[albitz]

It will rev freely in neutral because it isnt connected to the transmission. A soon as you put it in gear and let the clutch out it becomes connected to the wieght of the rest of the car and the lightened flywheel counts for nothing, so it wont rev quicker
 going up the road. Thats my understanding of it anyway.
The only advantage I could see is that it would make double declutch gearchanging quicker.

[Omega6pot]

It definately makes it quicker up the road, well it did on my vectra, instead of the engine spinnin a 15kg flywheel it only has to turn a 5.6kg one, thus making it able to rev up quicker

[Entwood]

It definately makes it quicker up the road, well it did on my vectra, instead of the engine spinnin a 15kg flywheel it only has to turn a 5.6kg one, thus making it able to rev up quicker

AFAIK when in gear the engine revolutions are directly linked to those of the back wheels (on an omega anyway)

I think that the difference of 10 kg in the flywheel might just be lost on the 1900 Kgs of the car !!!

Check Newtons Laws ... inertia can only be overcome by energy .. not wishful thinking 

[aaronjb]

You guys are forgetting that a flywheel is not 10Kg of 'static' weight, it's 10Kg of rotational mass..

This explains it quite nicely, though obviously you need to do the calculations for the gear ratios of an Omega:
http://www.pumaracing.co.uk/FLYWHEEL.htm

I can't seem to find the gear ratios, so I can't do the calculation .. but here's a snippet from that article that relates to a Ford Puma:

I built an engine recently and managed to remove nearly 3 Kg from the outside of the standard flywheel - so that would be equivalent to lightening the car by over 100 Kg in 1st gear

A popular mod on the 300ZX was not only a lightweight flywheel but a lightweight carbon fibre prop shaft - I never got around to the prop shaft, but the flywheel made quite a difference (similar weight car, some 3200lb).  The difference, of course, was even more marked on my MR2, but then that only weighs ~1000Kg

Lightweight crank pulleys are popular on some engines for the same reasons, although then you're stepping into the minefield of harmonic dampeners and whether you believe you're reducing engine life by removing them..

(Also worth reading: http://news.carjunky.com/automotive/Rotational_Mass.shtmland http://en.wikipedia.org/wiki/Moment_of_inertia )

[pedroMV6]

As I understand it, a lightened flywheel is only any real use when you're revving the tits off an engine for certain applications - i.e racing.
I think on a road car, you'll lose a fair bit of torque - which kinda is the point of a V6 engine - and therefore it';ll rev alot more at higher speeds, using more fuel and getting irritable on long journeys.
In our BTCC BMW (way back when Nelson were a lad), we would have different flywheels for different circuits - lighter for, say, Croft, heavier for Thruxton (Croft being a shorter, point-and-squirt circuit, Thruxton having long and fast straights).

Up to you, naturally, but if it's for an every day road car, I'd not bother, but if it's just for fun, then you might be on to summat.

[aaronjb]

I think on a road car, you'll lose a fair bit of torque - which kinda is the point of a V6 engine - and therefore it';ll rev alot more at higher speeds, using more fuel and getting irritable on long journeys.

You'll feel like you've lost a bit of torque, granted.. but it won't 'rev a lot more at high speeds' - the gearing hasn't changed, just the rotational mass, so 70mph will still be the same RPM before and after..

Flywheels are heavy in road cars primarily so that the engine feels 'smooth' and is harder to stall when pulling away (because as you engage the clutch the stored energy in the flywheel is released back into the drivetrain & engine - with a lighter flywheel there's less energy there to release, so if you don't get the clutch & throttle right it's much easier to stall). (On a race car it's slightly different - you can use that stored rotational energy to help top speed at the expensive of acceleration. Though I'm betting the 'heavy' flywheel for long tracks was still many kilos lighter than a road car flywheel)

[pedroMV6]

I think on a road car, you'll lose a fair bit of torque - which kinda is the point of a V6 engine - and therefore it';ll rev alot more at higher speeds, using more fuel and getting irritable on long journeys.

You'll feel like you've lost a bit of torque, granted.. but it won't 'rev a lot more at high speeds' - the gearing hasn't changed, just the rotational mass, so 70mph will still be the same RPM before and after..

Flywheels are heavy in road cars primarily so that the engine feels 'smooth' and is harder to stall when pulling away (because as you engage the clutch the stored energy in the flywheel is released back into the drivetrain & engine - with a lighter flywheel there's less energy there to release, so if you don't get the clutch & throttle right it's much easier to stall). (On a race car it's slightly different - you can use that stored rotational energy to help top speed at the expensive of acceleration. Though I'm betting the 'heavy' flywheel for long tracks was still many kilos lighter than a road car flywheel)

Oh yeah, only a very few kg's in it to be honest, but the car weighed less than a fag packet!

[Kevin Wood]

IMHO, it doesn't make much sense in an Omega. I have gone from a 15kg flywheel to a 6kg flywheel in my Westfield, which weighs in at about 650kg and revs to 7400 RPM and I can't say there was a huge difference in performance. Might have made it a little quicker in 1st (which is traction-limited most of the time anyway) but in higher gears the dominant factor is the weight of the car (and an Omega has an extra tonne of that).

It does make quick gear changes a little easier due to the fact that the rev drop between gears happens quicker but the Omega's manual box is a bit agricultural anyway, IMHO.

If you are ditching the DMF make sure you also change to a sprung clutch driven plate to absorb the shocks in the transmission.

Be VERY careful if they are lightening a flywheel rather than fabricating a light one. You do not want it to be weakened and at risk of bursting.

Kevin

[feeutfo]

Better to fit a lower geared diff I would think?

[Broomies Mate]

Better to fit a lower geared diff I would think?

For the time and money, I would advise this too, but would suffer fuel economy if the OP travels a lot on motorways.

I personally dont see the point in a lightened flywheel on any car which isn't a track car // racing car.  The difference is negligeable.  My old 2.5 Vectra didn't see much gain with a lightened flywheel.

Perhaps the OP had a decent service at the time of the flywheel replacement on his Veccy?

[Omega6pot]

The difference in my vectra after fitting the flywheel was night and day, it was an st200 but it shouldnt really matter, engine felt respnsive and perky, coupled with noticable improvement in acceleration and strangely fuel economy.
As for my omega, im intending on using it as a weekend play thing, im putting a 3.7 lsd diff into it aswelll for the obvious benefits of circling 
Im not to worried about loss of torque as it will be up the revs most of the time anyway, i plan on remapping the car aswell, ive only driven one actually remapped ex police car omega and it really was a terreffic difference. The change over at 3.5 was so much stronger.