Quote:
Originally Posted by ssullivan
Thanks for the story Nautilus. Lots of good points. I do want to debate you on the fact that these parts are useless for mpg. Their impact may be almost negligible on the dyno but over 100k of gas/brake gas/brake, the cumulative affect of: simple weight reduction, rotating inertia reduction, reduced pumping load would add up. Drag racers have a saying "Start saving ounces and you will save pounds."
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Indeed:
if all rotating accessories (alternator pulley, crank pulley, power steering pulley, cam gear, flywheel) are replaced by lightweight versions,
if the stock alternator is replaced by a small light 60A racing alternator, and
if the car runs only in racing or in long, constant-rpm highway commutes, then MPG gains and engine responsiveness are visible and significant. In city driving, when the accessories fail, their repair or replacement is far more expensive than any monetary gain from fuel economy.
PS Manufacturers have been already moving towards intermittent-running accessories for the last 10-15 years. Electric-hydraulic or electric-motor power steering, variable-displacement A/C compressor, decoupler alternator pulleys. They sought the same kind of gains, not from making a part "lighter and easier to run", but not running it at all when it's not needed.