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Old 07-11-2019, 03:40 PM   #25 (permalink)
Master EcoModder
Join Date: Dec 2008
Location: Eugene, OR, USA
Posts: 290

Lord Vader - '15 BMW i3 REx
90 day: 35.06 mpg (US)
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Tire Inflation Pressure Testing:

Figuring this to be one of the quickest and easiest things to modify, I did some quick low speed testing at two different tire pressures, and long story short; there isn't much 'fruit' there.

Over an admittedly short test course of straight back country road of about 1 mile in length, using the on-board power consumption data at a speed of 36 mph on OEM Bridgestone Ecopia EP 500 tires, and climate control off, this is what I got:

Pressures F / R, 50 / 50 psi, Directions 1 / 2 in mi/kWh
7.2 and 5.7
7.1 and 5.7

Pressures F / R 33 / 40 psi (BMW Spec), Directions 1 / 2 in mi/kWh
7.3 and 5.6
7.3 and 5.5

So the only thing I think I have really demonstrated here is that the wind changed.

I know that empirically there has to be some difference there, as I could feel a clear change in ride firmness, but over that relatively short distance it does not seem to be significant and certainly does not show in the numbers. Frankly, getting more conclusive data is not going to be very easy given the high dependence of EVs on temperature conditions as well as difficulty in finding roadways to conduct a bunch of low speed test runs. I'll give it another shot at some point though, hopefully with a much longer test track and a slower speed.
2015 BMW i3 REx
2011 Ford Flex SEL AWD
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