Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: Omega6pot on 22 June 2010, 16:28:08
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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
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Dont see the point tbh,all it can do imo is allow the engine to rev up quicker when the transmission is in neutral. :-/
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ask Exec - he did that to his omega
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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
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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.
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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
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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 :)
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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 )
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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.
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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)
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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!
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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. :o
Kevin
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Better to fit a lower geared diff I would think?
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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?
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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 ;D
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.
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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. :o
Kevin
You mean get the Black and Decker out and whack some holes in it, Hmm, vented clutch. :D
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thought from posts on here, that the only differance in plod state of tune was the dif?
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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. :o
Oh yeah - I would also never recommend machining a flywheel to make it lighter..
Because let's face it, you don't want to end up with a car looking like this: http://boardroom.wscc.co.uk/cgi-bin/ikonboard.cgi?act=ST;f=3;t=52365
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You mean get the Black and Decker out and whack some holes in it, Hmm, vented clutch. :D
I sincerely hope not. ;D
Wherever you machine it you will lose strength. Drilling holes is probably a bad idea because the holes will act as stress raisers for the surrounding material.
The greatest benefit is to lose mass towards the outer edge of the flywheel as it is this mass that is accelerated to the highest speeds by the rotation of the flywheel and hence its' effect is multiplied by its' angular velocity.
Strength is most critical towards the centre of the flywheel which is subject to forces trying to pull the flywheel apart and also to the torque output from the crankshaft. This itself comes in pulses as each cylinder fires so there is a lot of vibration coupled into the flywheel at this point.
If you're going to machine a flywheel it is therefore better to concentrate on the outside and ensure enough strength is left towards the centre.
Go to someone who doesn't appreciate the job the flywheel is doing and it could cost you your ankles. :o There is a lot of energy stored in a flywheel and if it lets go at high RPM it will destroy everything in its' path, including the bellhousing, transmission tunnel and the parts of the biological seat-to-steering wheel interface that sit just the other side of the transmission tunnel. :o
http://www.youtube.com/watch?v=jBONiZ6Hv1c
The other thing which hasn't yet been touched on is that the flywheel acts as a heatsink for the clutch. Not really a problem in racing and fast road applications because the clutch is rarely required to dissipate a lot of heat except when accelerating from a standing start but try to tow a caravan through the Pennines and you might find a failure mode here. ;)
Kevin
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thought from posts on here, that the only differance in plod state of tune was the dif?
You are right, there is still no such thing than "police special -tuned" Omega. All engines, no matter what application was, are the same. Also, no different maps/ECU's were ever available from factory, nor dealers.
Urban legends live strong.
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thought from posts on here, that the only differance in plod state of tune was the dif?
had plod LSD on mine omega 3.0 and cant really see any different to standars diff
I got now 4.22 diff on 3.2 manual and this make huge different , but use some more fuel and top speed is 140MPH
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drove a 3.2 plod last month, bloody shifts compared to mine on petrol, revs 500 odd rpm higher at 70mph so it will drink fuel, which was one of the owners complaints.
offered to swap for my dif, he rightly refused saying he would look into lpg conversions, which sounds right to me. :y
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some police cars definately had chipped ecu's, i dont think vauxhall special vehicle services had anything to do with it, instead i think some police workshops did this to increase power for there drivers. Not wildy done perhaps but the ex-police car i had revved past 7 and really shifted, drank fuel something shockin aswell haha :y
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right then .....
Lightened flywheels.
the flywheel is there to store energy in the engine. This is used to smooth out the vibration caused by the pistons having to stop and turn round twice per revolution.
Heavy flywheel = better smoothing = low vibration
Light flywheel = worse smoothing = high vibration
applies when under load or at idle.
HOWEVER. Lightening the flywheel does have a very significant effect on the gearing. Because the rotational inertia is connected to the ground through the gearbox, then any reduction in rotational inertia has a greater effect in the lower gears. I'd make a reasonably-informed guess that taking 10kg out of the flywheel would cause the car to accelerate as if its 200kg lighter in 1st gear and then accelerate as if it were 125kg lighter in 2nd, right up to "no effect" in 4th.
DMF.....
the dual mass flywheel is something entirely different. Put simply, the DMF puts the majority of the vibration-smoothing weight on the gearbox-side of the clutch, where it can reduce drivetrain noise and vibration.
Changing to a single-mass unit could induce a bit of drivetrain noise, but you'd be hard-pressed to notice. Usual noise is a sort of "zizzle" coming from the gearlever at very low revs/high load.
hope this is of help - if I put all of the theory in this, we'd be here all week
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hope this is of help - if I put all of the theory in this, we'd be here all week
The links I posted had the theory ;) (At least for calculating lost 'mass' from lost rotational mass) And you're right.. it's long.. and boring..
Unless you like algebra of course :)
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I have to do that sort of thing for a living....!
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I have to do that sort of thing for a living....!
My condolences.. ;D
(I jest, I love the engineering, maths & physics that lies behind cars, as well as taking them apart & putting them back together better.. though I'm still not sure I'd want to do it as a job :))
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some police cars definately had chipped ecu's, i dont think vauxhall special vehicle services had anything to do with it, instead i think some police workshops did this to increase power for there drivers. Not wildy done perhaps but the ex-police car i had revved past 7 and really shifted, drank fuel something shockin aswell haha :y
Nah, they all run standard setup as retail cars
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some police cars definately had chipped ecu's, i dont think vauxhall special vehicle services had anything to do with it, instead i think some police workshops did this to increase power for there drivers. Not wildy done perhaps but the ex-police car i had revved past 7 and really shifted, drank fuel something shockin aswell haha :y
Nah, they all run standard setup as retail cars
This really is a tough one for some of us... Please, show me two things:
1. a chipped ECU for a petrol Omega with dyno-graphs before and after chipping
2. any evidence, other that hear-say, of any tuning of any Omegas made by GM or local representative (or the local police or whatever...)
After these I just might be able to accept the slight possibility that there may have been someone somewhere who has been able to really tune-up a petrol V6 Omega.
For the OP: you say you have "felt the Vectra being quicker" etc... any documents of the facts it really gained something by lightening the flywheel?
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This really is a tough one for some of us... Please, show me two things:
1. a chipped ECU for a petrol Omega with dyno-graphs before and after chipping
2. any evidence, other that hear-say, of any tuning of any Omegas made by GM or local representative (or the local police or whatever...)
Well, we know that aftermarket chips are available for earlier Omegas and I guess it's not impossible that the fitting of them might have been included in the Police spec. I have to say I'm with Tunnie, though. There's no evidence to suggest that any tuning was carried out on Police spec. cars.
As to dyno graphs, they are so easily "tweaked" to show what the punter wants to see as to be almost worthless, IMHO, unless you know the rolling road operator and are sure he operates a "no bull" policy, keeps the rolling road calibrated and does a proper coastdown to compensate out the losses.
For the OP: you say you have "felt the Vectra being quicker" etc... any documents of the facts it really gained something by lightening the flywheel?
You're really getting into difficult territory here because we're talking about dynamic power delivery where dRPM/dt is very important. Even a dyno won't show that because cars are generally tested on a dyno in a high gear with a fairly low dRPM/dt, so the effects of a lightened flywheel will not be noticeable.
A lightened flywheel absolutely won't affect the steady state power output of the engine, only when it is accelerating quickly (since less energy is absorbed accelerating the flywheel). I have great difficulty believing that it affected the fuel consumption.
Mods such as this are pure physics. You can calculate what they will change despite what the seat of your pants might be telling you. The seat of the pants will tell you that the car gets faster after you've washed it, after all. ;)
Kevin
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I know the basic physics behind this issue but still a dyno graph would show the changes in curves despite the overall horsepower or torque were the same. And, when claiming somenthing has changed in performance, you should have some facts. At least my arse-dyno is not that accurate and reliable that I could say something has changed/imprroved just by the feel
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some dynos measure at a rising rate - I suspect it'd be noticeable there.
I've just ordered an aluminium flywheel for the Holden, so I could do a "before and after" timing check - I have a GPS dete logger, so it'd be reasonably accurate.
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some dynos measure at a rising rate - I suspect it'd be noticeable there.
I've just ordered an aluminium flywheel for the Holden, so I could do a "before and after" timing check - I have a GPS dete logger, so it'd be reasonably accurate.
I have an old Race Technology AP22 accelerometer if you want to borrow it? A bit of work to do before I'll need it, I suspect. ::)
Kevin
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And you can download RaceChrono to your mobile phone (you'll need a GPS signal, so a phone with GPS or a separate bluetooth GPS is required) http://www.racechrono.com/
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Don't know much about car flywheels..but in the off road motorcycle world people who want to run "revvy" motocross bikes in enduro events that often (at times) require lower speeds and more engine tractability than a flat out MX race nearly always fit a heavy flywheel (stator) in the engine to "soften" the power delivery at low revs.So the opposite is what is being dicussed here I guess ?? :-?