Quote:
Originally Posted by JDKane527
Definitely agree. The Kinetic Energy affects how much inertia the rotating assembly has. Decreasing overall inertia has benefits.
Angular kinetic energy is defined:
KE = (1/2)*(Iw^2)
I = moment of inertia
w = angular velocity
The faster a mass is rotating, the more effect it has on impacting Kinetic Energy. The crank pulley and flywheel are rotating at the same angular velocity. The flywheel would make a substantially larger impact than the crack pulley would make.
KE = (1/2)*(Iw^2)
I,flywheel >> I,crankpulley
The alternator pulley is rotating much faster than the crank pulley due to the pulley diameter. It could be argued that lightening the mass of the alternator would have more of a benefit than lightening the water pump pulley as the water pump pulley diameter is similar to the crank pulley diameter. It could also be argued that lightening the alternator may or may not cause harmonics/resonances in the engine as the rotating mass has been altered.
KE = (1/2)*(Iw^2)
w,alternator >> w,crankpulley
The case of the driveshaft, I is altered while velocity remains constant before and after.
KE = (1/2)*(Iw^2)
I,carbon << I,steel
I = mr^2
As m,carbon ~= (0.5) m,steel
Correct me if I'm wrong, but I hear the radius is slightly less for the carbon driveshaft.
r,carbon ~= (0.99) r,steel
I,carbon = (0.5)(0.99^2) I,steel
I,carbon = (0.4905) I,steel
KE,carbon = (0.4905) KE,steel
It would help for angular acceleration of the assembly slightly and for braking, but would not have as large of an impact as lightening a component with a higher angular velocity.
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When talking about crank pulley affecting hp, you have to understand you're talking about two different things.
a lighter pulley won't have as much of an effect as an underdrive pulley.
An underdrive pulley will often be lighter as well, but it is reducing engine load from accessories by changing the rpm's of the accessories for a given engine rpm which reduces the engine load for accessories at any given rpm.
Anyone who tries to argue that under drive pulleys don't increase hp is smoking crack.
That would be like saying that super chargers don't increase load and take hp from the engine to operate.
Jaden