that 'rattle' was a
dying bottom end
Join Date: Jun 2009
Location: United Kingdom
(Automotive engineering degree, so unless anyone would like to argue I've been taught wrong)..
A flywheel, as mentioned by Ian and hinted at by others, stores rotational energy by 'momentum'. A heavier flywheel has essentially more momentum (basically but there are exceptions). The weight is part of the mass, which is used to calculate Inertia. Inertia x Rotational Speed = Energy. Less weight is less mass, less energy and therefore is less energy.
By reducing the mass of the flywheel the engine will rev more freely, and respond and pick up better.
However, the torque will be seriously affected, so the engine will lose power on hills, under load etc.
"Alfa Romeo make cars as good as a car can be.......briefly"