thinking of getting a billet lightened flywheel for my cossie what are the pro`s and cons cheers

 

better pickup is the main advantage i'd imagine. A disadvantage would be the engine braking i guess?

 

Pro's are quicker engine pick-up.. Cons are lack of money and less 'torque' when engaging the clutch etc.

 

dont u have to get it balanced with the crank an clutch etc?

 

them things on all four wheels that we spend so much money on making the car slow down are for braking - not the engine.

 

cheers guys

 

lol....i meant that with some lightened flywheels you tend to get too much 'braking' when coming off throttle, tends to give a less smooth drive. Obviously it's fine on a race car or summat, but for a road car i think it can be annoying.

If the car is 4x4 then just get the flywheel machined to match a 2wd item, seems to work well

 

are they different flywheels then.

im going to use a 2wd flywheel i think

 

A lightened flywheel will not be able to store as much kinetic energy as a heavy flywheel so you'd find your self having to down shift more for hills etc...think that sounds right lol

 

there aint many hills on Snetterton lol

 

LOL at some comments Id say if youve never used one, dont guess just to reply

Ive had a few cars with very much lightened flywheels, and some have more effect than others, but it just makes the car feel more lively, hard to put it in to words really, but if youve driven a motorbike compared to a big non turbo diesel and youl know some engines feel lighter and more revvy than others, well lightening the flywheel makes it feel closer to the bike.

Never had one that made the car feel worse in any way on the road though, nothing noticable on a modded car which has a lot more things to fuck drivability, like big clutches, big wheels, big turbos, whatever.

Wether its worth the cash on a Cossie i dont know (i expect Markk can tell you that), but at least my reply is relevant

 

ive had mine spun down in weight and balanced...works well, more lumpy at idle i noticed,

 

Will make the idle a bit lumpier, and as said does not store as much energy, so the revs drop quicker between gearchanges due to less inertia from flywheel, and so you get a better gearchange, quicker pick up also as it is not just the weight of the flywheel that you are having to combat, you spend energy accelerating it, and at 6000rpm it weighs a lot, just the same as balanced wheels make the car go faster than unbalanced ones as they need less energy to rotate a balanced object.
It will not be as smooth to drive especially low down due to cyclic vibration caused by engine firing pulses, which is the primary job of weight of a flywheel to smooth out.
A good mod for track use.
tabetha

 

What about 1/4 mile racing?

 

You seriously think the flywheel is going to make much difference?

Heres what i've found about them.

tickover will be worse.
Low RPM's slightly worse.

Better gear changes, easier on syncro's.

if the car is under powered it'l make a difference to the launch on the strip.

About it really.

 

I could possibly (only very very slighly) understand the idle appearing to be differant but ONLY if your using a flywheel with a smaller diameter i.e for a 5.5" clutch for instance, but a std diameter cosworth flywheel with a std size clutch - if lightening your flywheel has made your idle speed lumpy then theres something wrong.
iirc the std 4x4 flywheel is something like 13kg ? my flywheel with ring gear is 3.5kg and i use a triple plate 7.5" clutch, ive never noticed any differance in idle quality at all.
and the gains from it are massive, the whole engine feels smooth and that it wants to make power and get going, unlike most YB's that are very lethargic.
I would say that you have to have 'better'clutch control than with a large flywheel as it makes that car easier to stall, this is where the stored energy at slow speeds (only take up) is helpful, but ive never stalled mine in proper use.

 

You have to bear in mind that a stock flywheel is designed to hlp a fully laden 4 up road car pull away smoothly.

If you have lightened your car in any way you do not need all that inertia from the flywheel.

A lightened flywheel will increase acceleration with the results more noticable in the lower gears.

 

I know it makes a very big difference I went to lightened flywheel & the car was almost undrivable with my triple plate clutch, had to change back or not drive it on the street it was that difficult. Dont bother is my advice my old girl recorded all its fastest accleration times on a standard flywheel.

 

I expect it is other factors that led to the better times.

Simple physics, your engine will accelerate a low inertia flywheel faster than a high inertia flywheel.

Another thing to bare in mind for people sayng that eg a 4 kg flywheel is best. Two different 4kg flywheels may have very different moments of inertia depending on their construction and therefore behave totally different.

 

true - but is it significant compared to the inertia of the rest of the drivetrain/brake discs/wheels/tyres and the mass of the car?

where a lightened flywheel helps is in response of the engine when declutched. it makes matching the engine speed with gear selection quicker.

good point - it very much depends where that 4 kg is.

the disadvantage of a light flywheel, as rod has found, is that it makes it very difficult to pull away smoothly at low rpm.