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[serek]

I have witnessed a bit vibration on cold mornings until the engine heat up.. and a tiny flywheel may increase it, so personally I wouldnt go for x20xe clutch

cant feal any on his car, any differents comper to DMF

not very sure though, it might be shaft dampers also

soon as I get fetted to my car I will let you know results

[azza_126]

So where did you get the spacer from and how much did it cost?

[serek]

So where did you get the spacer from and how much did it cost?

there is bloke on manta forum who sale them for just under 30£ posted

[2woody]

I have a courtney 5.6kg jobby on the scimitar build, I've no idea how it feels yet as it doesn't have a prop shaft and many other things, but I can tell you the revs pick up very quickly indeed. 

There is a massive advantage in haveing a light flywheel, you can run through some simple calc (simple if you make some resonable assumptions). 

Assume the majority of the mass of the flywheel to be at 2/3 of the radius to make life easy, so imagine the flywheel to be spinning a large mass at 95mm from its centre. 

We'll work with 1kg to start with.

Multiply this 1kg on the flywheel through the first gear ratio of 3.81, and the final drive ratio of 3.9 (if thats the one you've got) and its like having an extra 14.6 kg strapped to you're wheel at 95mm from the centre for every 1kg on the flywheel. 

You can now equate this to an extra mass in the car by multiplying this mass by the ratio of "mass radius on the flywheel / radius of the wheel". 

So in first gear its like 4.4kg extra weight in the car for every extra kg of mass in the flywheel. 

And if you shave 10kg off with a courtney flywheel its like loosing 43kg off the weight of the car in first gear. 

This lowers to a 24kg reduction in car weight in 2nd gear, and 15kg in thrid. 



I've not done this calculation before, and I seem to have almost convinced myself while writing this that is might not have been worth the extra money

I was a little conservative with the assumptions, the majority of the mass is very near the outer edge making it more like 55kg of the weight of the car in 1st. 

hmm.....    I kinda hope I've got something wrong, I was under the impression it made a bigger difference

Bummer!

your calculation is basically sound. It's definitely a worthwhile mod to do.

think about it, reducing the flywheel weight by 1 kg has the same affect as reducing the car weight by 50kg or so. So for a typical 10kg lighter flywheel, then you'll accelerate as if the car weighed a third less.

I've recently fitted an aluminium flywheel to the Holden. the 0-80 time in 2nd reduced by 4 seconds.

Obviously the effect is reduced in the higher ratios

[Kevin Wood]

Another point about light flywheels is that the engine responds faster to the throttle and slows quicker when you come off it, so a quick blip of the throttle is all you need on a downchange instead of a blaaaarrrrrrp with a heavy flywheel.

Changing up, the engine loses revs much quicker so you can make a smooth change from maximum revs quicker and without the clutch getting punishment from an engine that's still doing 6500 RPM when you engage the next gear.

Downside is that you'll have less stored momentum in the engine from idle so it'll be a bit less forgiving in traffic and you need to get launches more accurate as it's easier to stall it.

It made a noticeable difference on all counts fitting a light flywheel to my Westfield (18kg->5.5kg) but that is a very light car compared to an Omega.

[Marks DTM Calib]

Trouble is that you need to know the inertia of the flywheels before and after lightning as its not the weight that is the key factor in calculating any gains. In theory you could make a heavier flywheel with less inertia!

[2woody]

ever tried calculating the rotational inertia of something ?

[Marks DTM Calib]

Never calculated it, have measure it a few times though 

The key point is that lighter is only better if done properly.