I know that lightweight flywheels let the engine rev faster, and let more of the power reach the wheels because less power is lost in the drivetrain due to lowered spinning mass, but I'm curious about an issue someone might face when swapping the flywheel on their street car. Does the lightened flywheel improve fuel economy, still because of the lighter rotational assembly? Or does the engine have to work harder to maintain revs because of the reduced inertia, thus sacrificing efficiency?

Anybody with a lighter flywheel experience any MPG changes?

 

i have thought about this also.

i came to the conclusion that in the city it increases fuel economy while on the hwy it decreaces it.

no proof though

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JohnD1079 &raquo;</TD></TR><TR><TD CLASS="quote">i have thought about this also.

i came to the conclusion that in the city it increases fuel economy while on the hwy it decreaces it.

no proof though</TD></TR></TABLE>

In theory it should increase your MPG in the city, but granted it takes some more throttle to get the car going from a stop, I think it cancels out. A lightened flywheel will only affect the rev delta over the time delta, i.e. rev faster or come down faster. If you have a constant throttle while cruising on the highway, I don't believe it will affect your mileage there, either.