Gravity Efficiency and Range

[Saksak]

This is not a Lucid problem. It’s an EPA problem. Would you, as CEO, decide to hamstring yourself with “realistic” numbers when your competition is using the EPA standard?

Try explaining to customers (I’m making up numbers): “The Lucid Gravity’s 380 mile advertised range is really better than the competition’s 420 mile advertised range because we use a more realistic measurement.” The vast majority of customers will see 380 miles vs. 420 miles and assume 420 is better.

Regardless of the EPA number, real world driving still puts the Gravity #2 in range in it’s class (but #1 in the Eastern Edge EV race), beaten only by the Cadillac Escalade with the whopping 205 kWh battery (and who here would rather drive that vehicle…)

 

[tmichael]

I think range is a comfort number - meant to assuage range anxiety. As most of us know, any more than 240 miles allows us to get to the point where we need a rest stop anyway. Range in the 300s tells us that pit stop doesn't have to have a fast charger and we won't be coasting in on the last watt of power. 400 says we might be able to get home and not fast charge in any event.

I know, in my case, I don't look at the MPGe. But, my wife's Polestar 3 can make it around town for days without recharging. I can make it across the state and back with 2 fast charges. I'm good with whatever range it is, as long as it is realistically over 300. I didn't buy it for the range - but I'm comfortable I will have multiple charging choices along the way.

Lots of great comments here - lots of people smarter than I am. I enjoy the dialog - long live the freedom of debate!

 

[CraZ8]

They need to post realistic numbers that reflect driving at 75-80 with bursts up to 95 and a few bouts of acceleration at that stoplight to humble the guy next to me in the AMG Merc

 

[BS8899]

Your comments are based on your personal experience which is OK but not an independent test. Out of Spec 70 mph tests show Rivian under performs EPA while Lucid is very close. I wish that OOS had a Gravity test to add to the comparison. It is myth that Lucid under performs EPA by 20-25% based on third party tests. Red line indicates EPA range in chart below

View attachment 38170

Appreciate your points. Fair questions. I've addressed these questions before but let me give a brief response:

>OoS's data:
.....inasmuchas I don't have the patience to sit and watch Kyle's saga videos, I do respect his work. But, in an earlier posting about 6-8 months ago on this forum (you can look it up), I raised the questions regarding to Kyle's 70 mph run-dry tests done in Ft Collins. Specifically, the 5,000ft plus elevation in Ft. Collins AND the 'run-dry" (empty battery) test Kyle conducted tends to exaggerate the efficiency of the EVs under test, not just Lucid. The high elevation has significantly lower density air which translates to lower drag at high speeds. Second, "run-dry" adds another adder to the range. These two factors alone can exaggerate the achievable range of an EV (not just the Lucid) in excess of 10-15 % when compared with a sea-level test against the spec'd usable battery capacity.

It is also amusing to hear Kyle recently bemoaning about his Gravity only getting ~2.85mi/kWh. Well for one thing, he is now headquartered in North Carolina, much closer to sea-level and his efficiency numbers are (to my knowledge) not from running the battery dead! I don't think he will get to Lucid's implied efficiency of ~3.6 mi/kWh, but if he takes his Gravity back to Ft Collins and run it dry, I am sure he can break 3.0 mi/kWh.

To summarize,

Yes, I am sharing my own data and mine is not a fully controlled experiment. But I can explain the discrepancies against the chart you posted.

> My Rivian data:
....indeed it was my own data. It was done on my 2023 R1S, in "CONSERVE" mode. My 2023 R1S is quad motor (Bosch). It can be run in "Conserve" mode using only two motos. That, by itself, adds about 7-8% range to the SUV. My data is not a one-off. It was taken on multiple 780 mile trips on I-5/CA Hwy 210/I-10 between Sausalito and Paradise Valley. I DON"T claim it to be a "controlled experiment" per se because I don't regulate the other variables such as temperature, elevations, etc.. I drove almost exclusively at night where there is little traffic. I am confident about the repeatability of my results.

For grins, about a year ago, driving in Phoenix, I drove on 7th Street from Glendale to McDowell (~5 miles, I think), in my Rivian. I posted a shot of that event in this forum. I had green lights all the way and I registered an efficiency of >5mi/kWh, in a Rivian R1S!!!! Beat that! Obviously, that was a fluke, but it was real!

 

[illopp00]

Also, what about wind resistance at speed? The 5-cycle test is done in a room on a dynamometer, correct?

Correct, although that is what that fudge factor is, that the OEM has all the design data for simulating and estimating that effect. But since it's both temperature and pressure dependent you get huge variation (basically air density at speed). And I don't know how they weight it in the different of the 5 cycle tests, its a distance covered over certain temperature.

 

[illopp00]

They need to post realistic numbers that reflect driving at 75-80 with bursts up to 95 and a few bouts of acceleration at that stoplight to humble the guy next to me in the AMG Merc

OOS does now have a test track for getting some numbers for the Enthusiast under some fun scenarios

 

[Adnillien]

.....inasmuchas I don't have the patience to sit and watch Kyle's saga videos, I do respect his work. But, in an earlier posting about 6-8 months ago on this forum (you can look it up), I raised the questions regarding to Kyle's 70 mph run-dry tests done in Ft Collins. Specifically, the 5,000ft plus elevation in Ft. Collins AND the 'run-dry" (empty battery) test Kyle conducted tends to exaggerate the efficiency of the EVs under test, not just Lucid. The high elevation has significantly lower density air which translates to lower drag at high speeds. Second, "run-dry" adds another adder to the range. These two factors alone can exaggerate the achievable range of an EV (not just the Lucid) in excess of 10-15 % when compared with a sea-level test against the spec'd usable battery capacity.

The altitude does not matter for side by side comparison if all cars are tested the same and it actually goes against your argument that Rivian beats its EPA estimate.

 

[BS8899]

The altitude does not matter for side by side comparison if all cars are tested the same and it actually goes against your argument that Rivian beats its EPA estimate.

Altitude matters in a number of ways:

> if you are looking at absolute efficiency numbers, and that was what Kyle was comparing to, the lower drag at high altitude will exaggerate the achievable range.
> As you know, Lucid also claims it has one of the lowest drag coefficients. And Kyle called the Rivian "A Brick". Indeed, the Rivian has a much higher coefficient when compared to the Air. Likewise, Gravity has a higher drag coefficient as well. As such, the efficiency penalty for sea-level vs 5,000+ft elevation is much more pronounced.

Do you disagree? I thought it is just basic physics.

 

[BS8899]

Altitude matters in a number of ways:

> if you are looking at absolute efficiency numbers, and that was what Kyle was comparing to, the lower drag at high altitude will exaggerate the achievable range.
> As you know, Lucid also claims it has one of the lowest drag coefficients. And Kyle called the Rivian "A Brick". Indeed, the Rivian has a much higher coefficient when compared to the Air. Likewise, Gravity has a higher drag coefficient as well. As such, the efficiency penalty for sea-level vs 5,000+ft elevation is much more pronounced.

Do you disagree? I thought it is just basic physics.

Does change with elevation and temperature

Does​

The coefficient of drag (Cd) does change with elevation and temperature. As altitude increases, the density of the air decreases, which leads to a decrease in the drag force experienced by an object moving through the air. This is because the drag force is proportional to the square of the speed of the object in the fluid. Therefore, at higher altitudes, the drag force is less due to the thinner air.

Wikipedia+1

Temperature also affects the drag coefficient. As temperature increases, the viscosity of the air increases, which can lead to a higher drag force. However, the effect of temperature on drag is complex and depends on various factors, including the Reynolds number and Mach number.

Wikipedia

In summary, while altitude and temperature can affect the drag force experienced by an object, the drag coefficient itself is a function of the object's shape, the flow conditions, and other factors, and is not directly influenced by altitude or temperature.

Wikipedia+1

 

[BS8899]

Does change with elevation and temperature

Does​

The coefficient of drag (Cd) does change with elevation and temperature. As altitude increases, the density of the air decreases, which leads to a decrease in the drag force experienced by an object moving through the air. This is because the drag force is proportional to the square of the speed of the object in the fluid. Therefore, at higher altitudes, the drag force is less due to the thinner air.
Wikipedia+1
Temperature also affects the drag coefficient. As temperature increases, the viscosity of the air increases, which can lead to a higher drag force. However, the effect of temperature on drag is complex and depends on various factors, including the Reynolds number and Mach number.
Wikipedia
In summary, while altitude and temperature can affect the drag force experienced by an object, the drag coefficient itself is a function of the object's shape, the flow conditions, and other factors, and is not directly influenced by altitude or temperature.
Wikipedia+1

I think @Adnillien's argument is, the DRAG COEFFICIENT should be dimensionless. As such, it is not altered by altitude.

While that might be "true" up to a point. and if all of the experiments were run at the same time, at the same temperature and humidity etc., what @Adnillien argument might be correct. However, that wasn't how the experiments were run. Furthermore, I already said that my R1S data was based on operating in "CONSERVE" mode, which, by Rivian's documentation, adds 7-8% to the range (at sea=level, I presume). That alone almost explained most of the differences you saw on the chart.

When Kyle compares his data, ran at 5,000 ft to a totally depleted battery, it cannot be compared to Lucid (or Rivian's) claims, which, I presume, refer to "sea-level/temperature" etc..

As such, I maintain that Kyle's data ran at Ft Collins should not be used to compare to the manufacturer's claims. It is simply invalid because of the factors I cited. I am not saying Kyle did those tests incorrectly on purpose. He was based in Ft Collins, and he ran the tests there. Nevertheless, important differences were not comprehended. I've been to and driven in Ft Collins. and all over the mountains in Colorado. Cars DO perform differently in altitude!

If I am wrong, I'd gladly listen to a physics-based argument what I am missing.

Kyle should re-run all his comparisons at sea-level and revised the database.

 

[Adnillien]

I think @Adnillien's argument is, the DRAG COEFFICIENT should be dimensionless. As such, it is not altered by altitude.

I did not say that drag coefficient was dimensionless and that altitude does not impact range. Please do not put words in my mouth to support your argument. It changes the discussion from technical to personal which is frowned upon here on the forum. I stated that Kyle and OOS were testing the cars in the same method which allows for a comparison between cars. All real road test data is flawed by daily weather and traffic conditions and some error bars need to be applied to all of the data. The more effort goes reviewer to create similar operating conditions, the better their data will be. I think Kyle does a pretty good job on this standard.

My point is that you have stated multiple times on this forum that Rivain exceeds or comes closer to EPA estimates than Lucid. Clearly Kyle's data says otherwise and Kyle is using data which by your own analysis benefits Rivian more than Lucid.

 

[BS8899]

I did not say that drag coefficient was dimensionless and that altitude does not impact range. Please do not put words in my mouth to support your argument. It changes the discussion from technical to personal which is frowned upon here on the forum. I stated that Kyle and OOS were testing the cars in the same method which allows for a comparison between cars. All real road test data is flawed by daily weather and traffic conditions and some error bars need to be applied to all of the data. The more effort goes reviewer to create similar operating conditions, the better their data will be. I think Kyle does a pretty good job on this standard.

My point is that you have stated multiple times on this forum that Rivain exceeds or comes closer to EPA estimates than Lucid. Clearly Kyle's data says otherwise and Kyle is using data which by your own analysis benefits Rivian more than Lucid.

Did you watch Kyle's 5,000 mile Gravity video? He was bemoaning that he only got 2.85-2.9 mi/kWh, not the 3.6-3.7 mi/kWh Lucid claimed. Those are his words, not mine.

I have stated repeatedly that Lucid has one of the, if not THE, most efficient EVs around. What I object to is the exaggeration Lucid and its supporters amplify how MUCH Lucid is better than the competition. I am not attacking you personally. I think you are very smart person. But, I will contest arguments that don't make any physical sense.

 

[Adnillien]

Did you watch Kyle's 5,000 mile Gravity video? He was bemoaning that he only got 2.85-2.9 mi/kWh, not the 3.6-3.7 mi/kWh Lucid claimed. Those are his words, not mine.

I did not because it was too long and that video was for entertainment not efficiency testing.

I am not attacking you personally.

Putting untrue words in my mouth that I did not say is a form of personal attack.

 

[BS8899]

I did not because it was too long and that video was for entertainment not efficiency testing.


Putting untrue words in my mouth that I did not say is a form of personal attack.

Can you please be specific, what "Untrue words in your mouth"?

 

[BS8899]

My statement did NOT say "@Adnillien SAID Drag Coefficient is dimensionless". But when you compared 4 different vehicles, tested at different times, under different (untracked) temperatures, atmospheric condition, etc., you are effectively treating the Drag Coefficient as dimensionless. How else would you interpret it?!

You can dispute that, as you had. But I never said YOU SAID THAT.

Reality is,
[1] Kyle's 70mph tests he ran in Ft Collins is highly suspect because of the factors I cited. Again, I am NOT accusing Kyle of misrepresentation. I think it (altitude) is a "detail", albeit an important parameter, was not properly considered. Frankly, those tests should be run over again at sea-level.
[2] again, I think Lucid has some industry-leading capabilities. But exaggeration and muddle tests won't get Lucid to the finish line.

 

[doubletwist]

Here's my take on the EPA range issue.

The fault lies with BOTH the EPA and with Lucid.

Yes, the EPA range tests are both stupidly complicated (2 different tests and the manufacturer can use whichever one they want? That's just dumb) and both are wildly unrepresentative of American driving habits. So, yes, the EPA needs to fix that.

At the same time, while Lucid has not broken any rules, in an attempt to bill themselves as the most efficient EV by a large margin, they have chosen to advertise the efficiency and range based on the test they KNOW is far less accurate, and which they know darn well no customer is ever going to see on a regular basis, if ever.

That leaves a bad impression when people buy the car that's advertised as having a massively longer range than the competition, but then finding that its real world range isn't even close.

Just because they have the legal right to advertise that range, doesn't mean that it's a good idea from a brand reputation standpoint, and I think they (and other manufacturers as well) would do well to remember that.

In a year or so when people are watching or reading reviews of the Cosmos and a BMW iX3, and for one the reviewers say it doesn't come close to the advertised range, and for the other they say it meets or then goes farther than the advertised range, there's no way that doesn't become a real, measurable factor in which dealership/showroom they go to first, or which car they decide to buy.

 

[erigion]

Here's my take on the EPA range issue.

The fault lies with BOTH the EPA and with Lucid.

Yes, the EPA range tests are both stupidly complicated (2 different tests and the manufacturer can use whichever one they want? That's just dumb) and both are wildly unrepresentative of American driving habits. So, yes, the EPA needs to fix that.

At the same time, while Lucid has not broken any rules, in an attempt to bill themselves as the most efficient EV by a large margin, they have chosen to advertise the efficiency and range based on the test they KNOW is far less accurate, and which they know darn well no customer is ever going to see on a regular basis, if ever.

That leaves a bad impression when people buy the car that's advertised as having a massively longer range than the competition, but then finding that its real world range isn't even close.

Just because they have the legal right to advertise that range, doesn't mean that it's a good idea from a brand reputation standpoint, and I think they (and other manufacturers as well) would do well to remember that.

In a year or so when people are watching or reading reviews of the Cosmos and a BMW iX3, and for one the reviewers say it doesn't come close to the advertised range, and for the other they say it meets or then goes farther than the advertised range, there's no way that doesn't become a real, measurable factor in which dealership/showroom they go to first, or which car they decide to buy.

This is me (and probably a lot of people) with the R2 and Cosmos. If Cosmos's range/efficiency is as inflated as it is for the Gravity, why should I wait another year when I could get into an R2 at the end of this year when it's probably only a little less efficient and it has a larger rear seat (at least head room wise)?

Lucid needs to look at themselves in the mirror and rethink how they advertise their range/efficiency. You see this in ICE cars. Buyers will absolutely notice if they're not getting anywhere close to the advertised MPG and they'll complain. Those complaints will be found by people looking for new vehicles which will absolutely turn away some buyers. Look at Edmund's EV range test page and how the Lucid Gravity with all-seasons stacks up with other EVs. It looks bad when those bars are so far apart.

 

[illopp00]

This is me (and probably a lot of people) with the R2 and Cosmos. If Cosmos's range/efficiency is as inflated as it is for the Gravity, why should I wait another year when I could get into an R2 at the end of this year when it's probably only a little less efficient and it has a larger rear seat (at least head room wise)?

Lucid needs to look at themselves in the mirror and rethink how they advertise their range/efficiency. You see this in ICE cars. Buyers will absolutely notice if they're not getting anywhere close to the advertised MPG and they'll complain. Those complaints will be found by people looking for new vehicles which will absolutely turn away some buyers. Look at Edmund's EV range test page and how the Lucid Gravity with all-seasons stacks up with other EVs. It looks bad when those bars are so far apart.

Here is some new real world data, Trip A I usually reset every full battery (so 117kwhr), temps are mild in the 60-70s, I even drive like EPA with the HVAC off for a bit on since last charge.

 

[BS8899]

I thought this chart I come across (albeit provided by Rivian), might add some contrast to a prior discussion RE: how much more efficient is Lucid compared to Rivian.

As I drive my AGT and my Rivian R1S (Quad motor, Gen 1, in Conserve Mode, large pack) I claimed that I can get ~2.5mi/kWh when driving at night, on I-5/CA210/I-10 @75mph with my Rivian. It is still less efficient than my AGT (avg ~3.5mi/kWh), but the difference is not as big as some suggest.

Rivian's "Conserve Mode" (Gen1) uses FWD (as opposed to Quad) and lowers the height to reduce drag. If you believe the attached curves, Gravity's realizable (vs claim) efficiency is not dramatically better than an R1S in Conserve Mode. As for the assertion about tire wear in Conserve Mode, I am sure it is real. I rotate my tire s 2-3X per year (free at Discount Tires, as suggested by Rivian) I have not noticed any significant asymmetrical (front v s rear) tire wear differences.

Don't want to get into a debate about it. Draw your own conclusions.

 

[PCMc]

Also, what about wind resistance at speed? The 5-cycle test is done in a room on a dynamometer, correct?

The vehicle dynamometer testing done on a chassis rolls does factor in wind resistance. Manufacturers need to determine what a generally referred to as the A B C coefficients for the vehicle before doing the testing. This refers to the coefficients for driving resistance as a function of vehicle speed expressed as a quadratic equation. This is used to represent the resistance coming from not only aerodynamic drag but also rolling resistance, i.e., rolling friction from the tires plus also friction from rotating joints such as wheel bearings, etc. The way these coefficients are determined are using an actual vehicle on a test doing a series of coast down curves. These resulting factors, along with the vehicle test weight get programmed into the dynamometer controller with the resulting dyno resistance intended to match a vehicle at speed on the open road as closely as possible.

I think @Adnillien's argument is, the DRAG COEFFICIENT should be dimensionless. As such, it is not altered by altitude.

The drag coefficient is indeed an unitless/dimensionless term. At least as taught to me during my aerospace degree.

The formula for aero dynamic drag multiples the drag coefficient by an air density term, an area term (representing the frontal area of the vehicle), and then the velocity squared. It is the air density term which is a function of both altitude and temperature.

While Lucid may suggest waiting 2,000 miles it actually is typically more like 4,000 miles that is used as a vehicle break-in period before any testing such as the EPA range or ICE vehicle emissions/OBD testing is performed. My experience tracking my efficiency stats on my current 2023 Tesla Model S actually tended to suggest I didn't see "mature" efficiency numbers until more like 7,000 miles.

Your mileage may vary.