.23Cd ?

[Jeff N]

@Jeff N posted a sample of the P90D which is rated 64 MPGe under CR's city cycle vs 102 MPGe on EPA city, so the city test does skew very poor for Teslas (probably what you mentioned, extra acceleration and less chance for regen).

I was off-line for the last day or two so I'm just catching up now. I know my post says these MPGe numbers are for a P90D but I shifted Model numbers a couple times while looking up the quoted estimates and thought Ihad settled on using 90D rather than P90D. I'm too lazy now to go back and verify exactly which Model S version the MPGe Tesla numbers are for. Either way, the bottom line is that the Model S scores unusually low City MPGe numbers using CR's test methodology vs EPA. CR is generally harsher on city estimates than EPA but the Model S exaggerates this effect even more.

How useless is it to tell us the temperature that the AC is set at? Temperature difference is what matters.

True, although I loosely repeated their test while driving in the CA Central Valley with no visible wind on CA-99 at an average speed of 74 mph (CC set to 76 mph with occasional brief and mild slowdowns during almost 100 miles). Subsequently someone looked up weather records online which indicated I could have had a 3-4 mph tailwind. Or not. I had my A/C set to 73F as I recall and it was around 90F outside. When adjusted for around 58 kWh of battery energy I was on track to get around 190 miles of range which roughly validates their claim.

 

[SageBrush]

True, although I loosely repeated their test while driving in the CA Central Valley with no visible wind on CA-99 at an average speed of 74 mph (CC set to 76 mph with occasional brief and mild slowdowns during almost 100 miles). Subsequently someone looked up weather records online which indicated I could have had a 3-4 mph tailwind. Or not. I had my A/C set to 73F as I recall and it was around 90F outside. When adjusted for around 58 kWh of battery energy I was on track to get around 190 miles of range which roughly validates their claim.

I appreciate the careful reporting, so a couple of comments:

1. If average is 74 mph and tail-wind is 3-4, isn't average speed 70-71 mph net ?
2. Once the car cools down to the set-point, I imagine that ongoing cooling requirements are mostly sun radiation and then the hour of day and the angle to the sun affect the heat load considerably.

 

[stopcrazypp]

I appreciate the careful reporting, so a couple of comments:

1. If average is 74 mph and tail-wind is 3-4, isn't average speed 70-71 mph net ?

I think that's why most of these kind of tests when done officially have it done both ways to try to mitigate the advantage/disadvantage somewhat. There's still the issue of cross winds, but can't account for everything.

2. Once the car cools down to the set-point, I imagine that ongoing cooling requirements are mostly sun radiation and then the hour of day and the angle to the sun affect the heat load considerably.

I think that is why the CR test does away with AC/heat. Introduces a bit too many variables. There's also a slight but measurable difference in air resistance based on the temperature.

 

[SageBrush]

I think that is why the CR test does away with AC/heat. Introduces a bit too many variables. There's also a slight but measurable difference in air resistance based on the temperature.

Makes sense to me. I'm imaging one drive with the sun angle perpendicular and directly facing the windshield and another case where the sun is 60 degrees incident to the side glass. I'll guess the windshield has 50% more area, and the side window case only allows 50% penetration so up to ~ 4x fold difference in insolation through the day.

Your comment about air resistance reminded me that I see my best fuel economy in the summer even though I use cooling during my 90 - 95F, 6pm drive with the sun in the WSW while I drive southward. It is actually a good 10% better result than spring or autumn, which I still find hard to believe. A/C load at steady state is around 900 watts during this drive. If I was driving Jeff's car instead of mine, at 74 mph, the A/C overhead would be ~ 5%

 

[jsmay311]

Testing details aside, it does seem anecdotally true that Volt and Bolt owners seem to report being able to exceed the EPA estimates pretty easily while it seems to be the opposite case for Tesla owners.

There are lots of factors that could potentially explain why this is. But, still... it is what it is.

 

[Jeff N]

I appreciate the careful reporting, so a couple of comments:

1. If average is 74 mph and tail-wind is 3-4, isn't average speed 70-71 mph net ?

Maybe, but it's uncertain what the actual air speed and direction was exactly where and when I drove.

Also, I was being conservative on the implied range of 190 miles that I saw. It may have been up to ~205. So, that might compensate for much or all of any 3-4 mph possible tailwind. My results were not highly precise but they "fit" with C&D's basic claim.

 

[Zoomit]

Maybe, but it's uncertain what the actual air speed and direction was exactly where and when I drove.

Well I knew the day, time of day and general location and saw consistency across multiple weather station datasets.

 

[Topher]

1. If average is 74 mph and tail-wind is 3-4, isn't average speed 70-71 mph net ?

It's a car not a plane.

2. Once the car cools down to the set-point, I imagine that ongoing cooling requirements are mostly sun radiation and then the hour of day and the angle to the sun affect the heat load considerably.

Other way around, Cooling down is mostly dependent on the difference between inside starting temperature, and cooled temperature (plus both humidity levels). Once cooled down, the outside temperature becomes important. Whether solar gains or temperature gains dominate depends on a LOT of factors, but generally cars aren't well insulated.

Thank you kindly.

 

[ikjadoon]

An update. @stopcrazypp, it seems you were spot-on. CR admitted a few things recently.

1. They set their Tesla to the less-aggressive regenerative braking (this negatively impacts the Tesla more because of its massive weight)
2. They disable "extended range" modes, which presumably means the Tesla-set 90% daily charge limit
3. They made sure both cars had ~2 to 3k of miles only, so should be almost no degradation

That seems to explain it quite readily. Yes...Tesla's get 90% of their range when you set the battery to a 90% charge limit.

S 75D: :CR 235 miles vs EPA 259 miles: 91%
X 90D: CR 230 miles vs EPA 257 miles 89%

The "mystery" has been solved. Their quote:

• We make sure the car is in its version of normal drive mode, not extended range mode, because our goal is not to see what’s the maximum range an EV can get when pushed to its limits, but rather to see the total number of miles a driver should expect under normal circumstances.

I don't know what the Chevy Bolt uses? I've seen some people mention a default 90% limit as well and a default 100% limit.