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Old 05-02-2021, 02:59 PM   #17 (permalink)
Isaac Zachary
High Altitude Hybrid
 
Join Date: Dec 2020
Location: Gunnison, CO
Posts: 1,952

Avalon - '13 Toyota Avalon HV
90 day: 40.45 mpg (US)

Prius - '06 Toyota Prius
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Quote:
Originally Posted by serialk11r View Post
This really depends on the car, sometimes mechanical friction is the main source of inefficiency (taller gearing helps more), but other times it could be low combustion efficiency or high throttling losses.

Mechanical friction reduction from taller gearing has diminishing returns. If you have like 50-60% mechanical efficiency like my car at cruising conditions, slightly taller gearing drastically cuts down the friction and raises mechanical efficiency a lot. If you're at 80%, the gains are much much less, probably far less than half.

On cars with engines that are tasked with higher average loads, lean burn can be a tremendous help.
Taller gearing doesn't only lower friction, it also increases load. Load reduces throttling losses.
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