The advantages of a light weight flywheel are the same as reducing the weight of any part of your drive train you are going to get a quicker revving engine.
Advantages of lightweight flywheel.
The mass of a regular flywheel will be more thermally stable than would a lightweight one.
That is because the rotating mass is drastically reduced.
The flywheel also provides a more fluid cycling motion.
With a light flywheel you are constantly adjusting your pedalling speed.
The relevant basic physics relationships are which is the rotational analog to and.
Without the weight of the flywheel pedaling is more jerky and is more of an up and down motion which can add pressure on to your joints and can make you more susceptible to injury.
Though a lightweight flywheel does not create additional horsepower it does allow the engine to more rapidly transfer its power to the drive train.
There is no downside to the light flywheel.
Typical benefits of a lightweight flywheel.
I think there are numbers someone posted one time to bear out the flywheel part.
Btw in some cars e g e36 m3 the lightweight flywheel can results in a bit of a rattle.
There are significant benefits of an aluminum flywheel.
Lightened flywheels reduce drivability under most circumstances.
As for benefits i consider the flywheel and gears the best mods for sotp on a stock car.
At a given idle speed a lightweight lower moment flywheel will have less stored energy than the stock one so you have to adjust your clutch engagement and throttle input accordingly.
This is fantastic once you are moving because it means you will get to the higher rpms where the power is much quicker.
The lightweight one will have more problems with overheating and losing grip after such events.
The main advantage of a lightweight flywheel is that its reduced moment of inertia allows the engine to change its rotational speed more quickly.
I noticed the flywheel difference the very first upshift i made out of the garage.