# Study to increase range



## bwilson4web (Mar 4, 2019)

There was a range increase between the Std Rng Plus Model 3:

240 mi - my 2019
250 mi - the 2020
Expected, there has been a not surprising loss of battery capacity:

~240 mi - March 26, 2019, 50 miles odometer
~234-236 mi - April 28, 2020, 22,894 miles odometer
Recent HW 3.0 upgrade, the Nashville Service Center reported the tire tread depth:

Front: 6/6/6 driver - 3/3/3 passenger (original driver side tires)
Back: 7/7/7 driver - 4/4/4 passenger (newest tires)
In October, I hit a curb that required replacing the passenger side bearings. There was a delay getting the right rear tire aligned. So perhaps ~1-2,000 miles of badly aligned wheels and failing bearings which scrubbed the passenger side tires. So one option is to swap left and right side tires on the theory there may be a latent wheel alignment problem. At the same time, have the four wheel alignment checked. At best, this buys time to plan the next upgrade.

*DRAG TIMES TIRE AND RIMS*

I've been following the _Drag Times_ and other reports about how to get our Model 3 to accelerate faster. Solutions include:

ligher rims and tires - this reduces the polar moment of inertial and weight that allows faster acceleration.
lowering suspension - to reduce under body drag and wheel profile
front lip aero - to again reduce the frontal drag
rear trunk spoiler - to reduce the camel-back drag
very stick tires - often 300 or less wear factors
I appreciate these acceleration changes but my goals are not acceleration but longer range and higher efficiency. So my focus will be:

Rolling drag reduction - selecting tires for longer wear life, 600 or greater.
Confirm perfect wheel alignment - make sure the repairs have no latent defects.
Test tire temperature distribution.

Brake retraction clips to reduce latent brake pad drag.
Radiator inlet blocks (Prius trick)
Aero wheel hubs or well covers
Tuff testing the body (some road dirt suggests there may be problem areas)
Making changes without metrics to evaluate their effect is useless. My proposed changes require sensitive metrics.

*TESTING METHODS*

There are several approaches:

benchmarks
roll-downs
*Benchmarks*

My approach is to conduct three, +10 mile benchmarks that start and end at the same location:

65-70 mph - typically out, turn around, and back looking for aero improvements
45-50 mph - used to measure mid-speed metrics
25-30 mph - looking for low speed effects
Each benchmark begins with a practice run that also verifies the route is free from construction or accidents. Driving to the benchmark path ensures tires and drivetrain are warmed up. Starting and ending at the same location tends to even out wind effects which means testing 1-3 PM and 1-6 AM testing.

Adjusted for temperature, these three metrics define a quadratic equation: A(v**2) + B(v) + C defines the expected performance between the subsequent point above 15-18 mph.

*Roll-Downs*

The EPA publishes the roll-down coefficients for:

A (lbs/velocity**2) - corresponds to aerodynamic force
B (lbs/velocity) - corresponds to rolling drag
C (lbs) - corresponds to vehicle overhead
So following the protocol of SAE J1263, I tried to locally replicate but was disappointed. The full protocol requires 16 bi-directional passes on a sufficiently flat track. Using the closest road to the airport:









For my first tests, I used "Scan My Tesla" and "Speedometer" GPS records:









There were problems getting the same section of the test track. I'll have to re-run to identify the specific start and stop spots after doing a dash cam plot.
GPS data is notorious for having altitude challenges.











The South bound runs were consistent because I'd mapped the starting position accurately.
The North bound runs were less consistent so their runs, especially below 40 mph, had significant variance.
There is no altitude metric in "Scan My Tesla".
I'll have to survey the test track and get a better start positions identified on both the North and South bound routes. I also have a high-resolution, 6-axis accelerometer that can provide altitude changes as well as acceleration and derived velocity. Combining the data is doable but not trivial. Still, I should be able to get credible A, B, and C coefficients.

*SUMMARY*

I need reproducible metrics before making significant changes. The tire rotation and temperature survey is trivial ... normal maintenance. Once I know the metrics work, I'll be able to A-B-A test each change and hopefully, improve the 2019 Std Rng Plus Model 3 range to compensate for battery degradation and 2020 performance.

Bob Wilson


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## JasonF (Oct 26, 2018)

How did you drive past the airport that many times without getting arrested?


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## bwilson4web (Mar 4, 2019)

The road is not on HSV airport property. Furthermore, air traffic is all but shutdown after midnight. Testing after midnight avoids traffic and wind effects.

Bob Wilson


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## bwilson4web (Mar 4, 2019)

My alternate to the roll down benchmark works:









Perform at least three different speed, benchmark:
< 15 mph - Prius benchmarks show the maximum range in the 15-20 mph range. The low value sets the maximum range part of the parabolic curve to real world values.
> 20 mph - Set the range of the minimum power, curve, which in the Prius is 15-20 mph. We need the minimum power value to evaluate the effect at ordinary speeds.
40-45 mph - A middle range speed used for urban travel. Not necessary BUT in this case, accidentally having the heaters on result in a significant increase in Wh/mi.
65-75 mph - The high-speed benchmark gives a way to evaluate aerodynamic changes.

Use a "Three Point Parabola Calculator" or "Three Point Quadratic Calculator"
Use at least three benchmark points, more helps identify problem (see bad data point)

Unlike roll-down benchmarks, these can be performed in 1-2 hours. Also, the sensitivity of roll-down appears to be poor at slow speeds. Regardless, make sure to use a checklist to avoid problems like my unplanned heater test. Hold as many environmental parameters constant.

Bob Wilson


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