Thread: Prius 75-91mpg
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Old 08-28-2019, 01:44 PM   #113 (permalink)
Nathan jones
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Originally Posted by mpg_numbers_guy View Post
I recently hooked up the Dr. Prius app to my mom's 08 Prius to see how the battery functions while driving. The car seems to strive to keep the battery between a 60% and 65% state of charge - indicated by 6/8 bars on the display. Any higher than 63% means that you have either gone downhill, or have driven inefficiently by braking a lot, so the car will use more battery to try to get your mpg back up. Any lower than 60% means that you've used a lot of EV range or a lot of battery power, so the car will burn more gas to get the charge back up, also reducing efficiency.

Improving aerodynamics and reducing weight won't make the battery stay at a higher charge - the 60%-65% is optimized for best battery life and efficiency. Reducing weight will help keep the battery at that charge state better, which will allow the car to get better fuel economy overall.

It's a myth that hybrids get better fuel economy - most of their efficiency is due to their aerodynamic shape and smaller engine. The electric system works mostly to offset inefficient driving patterns, such as braking.

The shorter wheels theoretically should give you shorter gearing, but I'm not entirely sure how the Prius CVT works - it may be completely load based and not have any kind of rubber band style gear ratios (i.e., min RPM for a given speed). It would be interesting to see speed vs MPH on level ground with the old wheels/tires versus the new wheels/tires - using RPM monitoring through Torque or a Scangauge, and a GPS speedometer.
Thanks for your time and reply, I'm just going by a feel of the car. To begin with the acceleration was ruthless but over a few days the engine came on less and has gone back to how it used to be, energy wise. If you race for for a while it has more reserve power even though the ice works as normal. However the whole car certainly drives better, holds better and is less buffeted by the wind, compared to stock.

I agree about efficiency, I used to get 60mpg from my exes Ibiza. Mine on a run and round town however is far better and has low tax. I reduced weight because most of my miles are urban rural and I stop start all the time. I do agree that for long consistent runs aerodynamics is utmost but for me I feel weight is

Last edited by Nathan jones; 08-28-2019 at 02:03 PM..
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