Quote:
Originally Posted by jdubau55
Any weight removed from the vehicle improves MPG. Simple fact.
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Though I do agree with you that less weight is better for MPG, when were talking rotating mass, this is not true.
A crude explanation: as you start to decrease rotating mass by lightening things like the pulleys and the flywheel, MPG may suffer. The engine revs faster and once spun up it takes more gas to keep things going. Lower mass will take less time to dissapate the energy put into it. Toyota knows this and has designed certain portions of the drivetrain to take advantage of rotating mass for optimal mpg. The pullys are one of these portions. Gains or losses in mpg will be most noticeable on the highway. Around-town should remain the same or maybe get better. Maybe.

The main reason for a possible decrease on the highway is that the RPM at which the engine wants to 'cruise' will likely be eliminated. This is due to a less efficient energy storage system. Anyway, wtf do I know. With only the pulley changed out and the flywheel the same, there likely wont be much change.