R2 Highway Efficiency Test: 80 MPH vs 70 MPH Changed Everything

[ksurfier]

Ironically, I spent a great deal of time today along the central coast at 80 mph and even into a headwind (got 1.3 MPK - that was a first!). So I wouldn’t say it’s all that unusual…I’d say going less than 75 is extremely rare.

Edit: I pulled up to a sheriff going 80 (me) and was side by side, my wife suggested I slow down and I think it was a fair request…he dropped to 65 and created a 20-30 car pile up all going 65, then after 5-10 minutes pulled someone over for what was likely a cell phone…

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[Indy avocado]

EPA has dynomometer values that tend to very accurately predict "nice day highway" efficiency and range.

Below plots assume *very* light HVAC load.

Some summary

Efficiency:

Range:

My range model was forecasting this at 229 (+/-) at 80. If your data holds over longer distances, the model may be very optimistic.

I think your Model Y numbers are slightly pessimistic, possibly optimistic on R2, but very close to a perfect day range test. I am thinking 265mi (vs your 271) at sea level for the 21" Performance. The Model Y should be 285-295mi.

1. Direct testing: InsideEVs measured about 2.97 mi/kWh under favorable Colorado conditions.
2. Physics: The R2’s estimated CdA predicts approximately 2.5–2.7 mi/kWh at sea level.
3. Vehicle comparison: The R2 falls exactly between the Model Y and R1, where its estimated CdA places it.
4. Battery capacity: Multiplying 2.5–2.9 mi/kWh × 88 kWh gives approximately 220–255 miles usable, depending on conditions, with favorable conditions approaching 260 miles.

This all checks out.

My calculator finds 2.94mi/kWh @ 70mph and 5000ft elevation (20" AT). Sounds like it's spot-on with InsideEVs.
Adjusting back to sea level (above screenshots) and we get 2.67mi/kWh, just as #2

No, just kicked them...everyone was looking at me funny...

But ABRP shows the following (only a ~5% difference betweem 20" and 21")
R2 at 80 mph can travel ~190 miles (2.16 MPK)
R2 at 75 mph can travel ~200 miles (2.3 MPK)
R2 at 70 mph can travel ~213 miles (2.45 MPK)
R2 at 66 mph can travel ~225 miles (2.6 MPK)
R2 at 58 mph can travel ~250 miles (2.85 MPK)

These all seem to be pessimistic, as they should be for a route planning tool, but perhaps unnecessarily so?

Did some crude gpt calculations on incorporating charge times and distance traveled to see if charging more at 80 mph is worth it at any distance.

As a thought exercise I was curious to calculate the time efficiency of the R2 over long distance.
...
Bottom line, driving fast and charging more is faster on a long road trip than slower with less frequent charging sessions.

Lets compare with my calculator (uses discrete stops, estimates time from measured charging curves & 70mph range tests):
70 vs 80mph over 600mi, R2 saves ~38 minutes at 80mph.

Optimal travel speed is right around 85mph, but certainly diminishing returns over 75.

 

[3dogfl]

I imagine heavier-traffic on highway driving would have a significant positive impact on range. Coming from cycling passion where drafting is huge, even at our much lower speeds, and you don't have to be that close to feel the impact. When a vehicle passes you on the road, you can feel that boost for several seconds.

 

[Budman]

Air at 32F is also 15% more dense than air at 70F for the same elevation. The difference between 70F and 100F is 5% lower density at 100F.

This is an under appreciated fact. A good chunk of the loss of range in cold weather is just due to the air being much more dense in colder weather.

 

[Indy avocado]

I imagine heavier-traffic on highway driving would have a significant positive impact on range. Coming from cycling passion where drafting is huge, even at our much lower speeds, and you don't have to be that close to feel the impact. When a vehicle passes you on the road, you can feel that boost for several seconds.

Definitely my experience in my R1T that alternating 50-80miles an hour in heavy traffic around Chicago is more efficient than holding 65-70 steady on a rural road.

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