Any guesses on the Cd for the Model X? I'm sure that aerodynamics were the highest priority for range purposes. Do you think the coefficient of drag is lower than the Model S? I'm sure the CdA is higher.
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Any guesses on the Cd for the Model X? I'm sure that aerodynamics were the highest priority for range purposes. Do you think the coefficient of drag is lower than the Model S? I'm sure the CdA is higher.
As far as I know they did not "get rid of the side mirrors" tho?The fact that they managed to get rid of the side mirrors means that the Cd could be lower than the Model S. Their absence will also reduce the frontal area gain a little bit.
The fact that they managed to get rid of the side mirrors means that the Cd could be lower than the Model S.
The fact that they managed to get rid of the side mirrors means that the Cd could be lower than the Model S. Their absence will also reduce the frontal area gain a little bit.
wrong.The fact that they managed to get rid of the side mirrors means that the Cd could be lower than the Model S.
Well, let's see.
We think we know that the car has ~10% less range on the same battery (Sig XP90D @240 EPA vs SP90D @ 253 EPA "+6%" per Tesla.)
We think we know that the car is 1200 pounds heavier (a tech gave the weight as 6100 pounds to someone on the forum (Post#543 here,) and that's consistent with the promised 0-60 times vs the model S 0-60 times.)
We think we know that the X is 198" long, 66.3" high, and 89.4" wide with 7.2" ground clearance vs the S's 196" length, 56.5" height, 86.2" width, and 5.6" ground clearance. The S is 77.3" with the mirrors folded. (Post#447 here:)
We assume the same powertrain efficiency and the same tire/drivetrain rolling resistance per pound.
With a 24% heavier car, the rolling resistance should be 24% higher - but rolling resistance is typically a small factor at freeway speeds compared to aerodynamics.
The X is (66.3-7.2) 59" tall vs the S's (56.5-5.6) 50.9" - 16%% more cross sectional area. Assuming the same mirrors, it's also 3.2" wider = 4% more cross sectional area.
If rolling resistance had no effect, the Cd has to be ~9% lower to get the demonstrated range with ~20% more frontal area. If rolling resistance is 50% of the freeway number, Cd has to be at least 20% lower to get the range shown - because the losses from rolling resistance exceed the demonstrated range loss, and the car has to have a lower overall CdA.
The reality is presumably somewhere in between these two cases assuming our baseline "facts" are correct.
Walter
As a mathematician I'm slightly annoyed with the frequent misuse of exponentially :tongue:As the drag of side mirrors will increase exponentially.
Well, let's see.
We think we know that the car has ~10% less range on the same battery (Sig XP90D @240 EPA vs SP90D @ 253 EPA "+6%" per Tesla.)
We think we know that the car is 1200 pounds heavier (a tech gave the weight as 6100 pounds to someone on the forum (Post#543 here,) and that's consistent with the promised 0-60 times vs the model S 0-60 times.)
We think we know that the X is 198" long, 66.3" high, and 89.4" wide with 7.2" ground clearance vs the S's 196" length, 56.5" height, 86.2" width, and 5.6" ground clearance. The S is 77.3" with the mirrors folded. (Post#447 here:)
We assume the same powertrain efficiency and the same tire/drivetrain rolling resistance per pound.
With a 24% heavier car, the rolling resistance should be 24% higher - but rolling resistance is typically a small factor at freeway speeds compared to aerodynamics.
The X is (66.3-7.2) 59" tall vs the S's (56.5-5.6) 50.9" - 16%% more cross sectional area. Assuming the same mirrors, it's also 3.2" wider = 4% more cross sectional area.
If rolling resistance had no effect, the Cd has to be ~9% lower to get the demonstrated range with ~20% more frontal area. If rolling resistance is 50% of the freeway number, Cd has to be at least 20% lower to get the range shown - because the losses from rolling resistance exceed the demonstrated range loss, and the car has to have a lower overall CdA.
The reality is presumably somewhere in between these two cases assuming our baseline "facts" are correct.
Walter
Calculations would make more sense if highway range was known where Cd is the biggest factor. Using EPA range skews result since Cd is only one of many factors affecting range in EPA mileage test.