Lighter flywheels and their effect on hills

[obi_waynne]

I'm hoping that someone with a lighter flywheel can settle this debate for me.

I'm fairly reliably told that "a car with a flywheel will lose forward momentum on a hill" is an old wives tail. But I really want some more feedback to see if there is an element of truth in this.

I see that the engine with a lighter flywheel responds more quickly to a drop or rise of revs, and surely on a hill this will translate into a faster drop in revs, unless the throttle is increase.

However it is difficult comparing this premise with a standard flywheel equipped car.

The lighter flywheel will increase the power output of the engine so will this offset the "hill drag" effect or is the "hill drag" really an old wives tale?

Does a car with a lighter flywheel lose momentum on a hill?

 

[stamford]

A car with a lighter flywheel will lose momentum uphill purely because it cannot store the kinetic energy that a higher mass flywheel can to keep the engine spinning, however if the power can be kept on in its power band then the drop will be minimal. On the flat an engine running a lighter flywheel can rev quicker therefore reach its power band much quicker.

 

[The JAF]

Exactly what staford said. The flywhell maintians inertia and makes for smoother running. The lighter the flywheel the less inertia there is and the lumpier the idle. This also means that the engine will rev quicker and more freely but will also slow down just as quick. So its not an old wives tail but you only notice it because it will drop speed a bit quicker than a standard one.

But be careful some clutch and flywheels kits dont actually save much weight because even though the flywheel is lighter the clutch cover and plate is normally stronger and heavier.