omega0684
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| posted on 17/10/09 at 11:31 PM |
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Lightened Flywheels & Materials?
at present on my pinto im running a steel 5kg flywheel (with ring gear fitted).
i know one chap that is running a solid steel fly on his pinto that is 3.65kg and the pinto itself pushes just over 200bhp.
just how light can you go with a flywheel, what are the advantages of lightening them (increased acceleration etc?) but what are the disadvantages.
can they be so light that they can't turn over the engine and does loss of weight in the fly mean loss of torque in the engine.
i was even having a discussion earlier with clairetoo about billet ali flywheels, what are people opinions on this idea, again advantages and
disadvantages please
all opinions welcome
Alex
[Edited on 17/10/09 by omega0684]
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blakep82
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| posted on 17/10/09 at 11:40 PM |
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will be watching this myself 
found this on a quick search of the intermaweb
http://passionford.com/forum/general-discussion/246191-what-advantages-disadvantages-if-lightened-flywheels.html
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liam.mccaffrey
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| posted on 17/10/09 at 11:53 PM |
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if you look at it mechanically, a lighter flywheel will have a lower moment of inertia and will therefore change rpm more freely. Be it revs rising
or falling.
Newtons second law for rotation shows that an applied torque = the moment of inertia x angular acceleration
so reducing the mass of the flywheel and keeping the applied torque the same will yield a higher angular acceleration and a resultant higher vehicle
acceleration
[Edited on 18/10/09 by liam.mccaffrey]
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norfolkluego
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| posted on 17/10/09 at 11:55 PM |
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Some good use of the English language on that link - innit.
What I would have thought a lightened flywheel would do is increase effective horsepower, i.e. you won't have any more coming down the
crank but you'll lose less at the flywheel therefore more gets to the rear wheels. But you will have to rev it harder pulling away, not really a
problem is it, who doesn't like revving an engine.
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andkilde
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| posted on 18/10/09 at 12:33 AM |
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Too light could result in poor idle, hunting, etc, though cars with super-hot cams apparently get improved idle from a light flywheel (don't
recall why, read it in a David Vizard book at some point in the past).
Lighter also means you need a more deft touch when starting off in 1st -- heavy=more stored energy= less likely to stall in 1st if you're
"ham-footed".
Too light can also an issue for heat transfer, ie if you're slipping the clutch and putting a lot of heat into the flywheel, a lighter one will
be more likely to warp than a heavy one.
I wouldn't go much under 5 kilos in a street driven car.
t
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gregs
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| posted on 18/10/09 at 07:12 AM |
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Some useful stuff here linky
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MakeEverything
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| posted on 18/10/09 at 07:36 AM |
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Think Centrifugal Mass.
The heavier the flywheel, the more power needed (Losses) to turn the heavier mass. However, as said above, heavier prevents stalling and having to
REV the engine more. I think a lighter flywheel also affects the smoothness of the engine. A Lighter flywheel should make the engine more responsive
though.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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snapper
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| posted on 18/10/09 at 07:39 AM |
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i have a light steel flywheel on my car and to be honest there is little difference to be felt.
if anything it revs more freely making for a more responsive drive and revs return to idle quicker.
There is a diagram of how to lighten a standard cast flywheel in the "How to Power tune the SOHC" book and that is the limit of what you
should do.
For a simple home job just get the thick outer ring on the back lathed off to the same thickness as the rest of the flywheel.
ARP bolts, thread lock and dowle if revs over 7000 on a continual basis.
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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Volvorsport
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| posted on 18/10/09 at 08:31 AM |
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www.ttvracing.com
www.dbsmotorsport.co.uk
getting dirty under a bus
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adam1985
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| posted on 18/10/09 at 11:51 AM |
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i know fitting a billet flywheel was supposed to be a brill mod for the v6 vauxhalls because they had a big lump off iron there but just be carefull
you dont take to much of as they have been know to shatter and the effects are quiet nasty 
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