johnlocke
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Re: Nissan Ariya to be announced for the JDM July 15, 2020

Sat Aug 01, 2020 4:11 pm

GRA wrote:
Sat Jul 25, 2020 7:46 pm
alozzy wrote:
Fri Jul 24, 2020 11:33 pm
johnlocke wrote:
Fri Jul 24, 2020 11:53 am

CD is only half of the equation. You also need to know what the cross-section area is. A car with a lower CD but larger cross-section could get worse mileage then a smaller car with a higher CD.
I'd.be very surprised if the Model 3 has a larger surface area on it's front end than the LEAF, so I still contend that the larger spread between "real world" and EPA for the Model 3 comes must be due to more aggressive driving vs the results for the LEAF.

LEAF: 71"W x 61-62"H = 4331- 4,402in.^2

Model 3: 73"W x 56-57"H = 4,088-4,161 in. ^2.

I suspect it has more to do with different temps and winds.
The numbers above don't reflect ground clearance or body shape. the Leaf is rather square in cross-section while the Tesla is more ovoid. Cross-section data for most cars is surprisingly hard to find. I suspect that it has to do more with the different temperature ranges during the drive tests. Colder weather while driving the Tesla would tip the scales. Different cars on different days and different weather. Not surprising that the results differ from the EPA numbers. The Tesla hit 74% of it's EPA range while the Leaf got about 85% it's EPA range. At 75 MPH that is surprisingly good and the Tesla still went 50 miles further than the Leaf.
2016 SV, New battery at 45K mi.
Jamul, CA
San Diego East County

GRA
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Location: East side of San Francisco Bay

Re: Nissan Ariya to be announced for the JDM July 15, 2020

Sun Aug 02, 2020 6:04 pm

johnlocke wrote:
Sat Aug 01, 2020 4:11 pm
GRA wrote:
Sat Jul 25, 2020 7:46 pm
alozzy wrote:
Fri Jul 24, 2020 11:33 pm


I'd.be very surprised if the Model 3 has a larger surface area on it's front end than the LEAF, so I still contend that the larger spread between "real world" and EPA for the Model 3 comes must be due to more aggressive driving vs the results for the LEAF.

LEAF: 71"W x 61-62"H = 4331- 4,402in.^2

Model 3: 73"W x 56-57"H = 4,088-4,161 in. ^2.

I suspect it has more to do with different temps and winds.
The numbers above don't reflect ground clearance or body shape. the Leaf is rather square in cross-section while the Tesla is more ovoid. Cross-section data for most cars is surprisingly hard to find. I suspect that it has to do more with the different temperature ranges during the drive tests. Colder weather while driving the Tesla would tip the scales. Different cars on different days and different weather. Not surprising that the results differ from the EPA numbers. The Tesla hit 74% of it's EPA range while the Leaf got about 85% it's EPA range. At 75 MPH that is surprisingly good and the Tesla still went 50 miles further than the Leaf.

AIUI, Cd is the factor that modifies frontal area, with 1.0 essentially being a rectangle normal to the airflow (the reference below shows a cube @ 1.05), although skin friction also has an effect (individual Model 3 panel gaps might hurt it as well):
The reference area depends on what type of drag coefficient is being measured. For automobiles and many other objects, the reference area is the projected frontal area of the vehicle. This may not necessarily be the cross-sectional area of the vehicle, depending on where the cross-section is taken.

https://en.m.wikipedia.org/wiki/Drag_coefficient


The practical way to know is to drive both cars in the same conditions and accurately measure power consumption, after first trying to take account of differences in rolling resistance (tires etc.). And unless testing takes place in the same wind tunnel, Cd will vary considerably for the same car.

To the extent possible, C&D does their range tests under the same conditions, but those obviously can vary.

They also tested their long-term Model 3 at the test track at Chrysler's proving grounds, which eliminates any altitude effects and reduces the effects of winds. I'm guessing the Model 3 was hurt by the lack of a heat pump, as C&D found heater use (they test all cars with the climate control set to 72 deg.) could knock over 60 miles off the Model 3's range @ 70 mph, with seats and heater both on:
How Much Does Climate Control Affect EV Range?

We cranked up the heat in our Tesla Model 3 to find out just how much of an impact it has.

https://www-caranddriver-com.cdn.amppro ... v-range%2F
Last edited by GRA on Mon Aug 03, 2020 4:53 pm, edited 1 time in total.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

SageBrush2
Posts: 11
Joined: Mon Aug 03, 2020 8:50 am
Delivery Date: 03 Oct 2013
Location: Albuquerque, NM

Re: Nissan Ariya to be announced for the JDM July 15, 2020

Mon Aug 03, 2020 10:41 am

johnlocke wrote:
Sat Aug 01, 2020 4:11 pm
The numbers above don't reflect ground clearance or body shape.
Those variable are reflected in the Cd.
The other car variable in calculating aero drag is frontal area, not surface area

width * height can be a pretty good approximation of frontal area but it is not exact and the error varies between cars. I'll guess that the main error comes from how the side mirrors are included in the width, and how much clearance varies between cars.

johnlocke
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Re: Nissan Ariya to be announced for the JDM July 15, 2020

Mon Aug 03, 2020 10:46 pm

SageBrush2 wrote:
Mon Aug 03, 2020 10:41 am
johnlocke wrote:
Sat Aug 01, 2020 4:11 pm
The numbers above don't reflect ground clearance or body shape.
Those variable are reflected in the Cd.
The other car variable in calculating aero drag is frontal area, not surface area

width * height can be a pretty good approximation of frontal area but it is not exact and the error varies between cars. I'll guess that the main error comes from how the side mirrors are included in the width, and how much clearance varies between cars.
Which is why I specified cross section, not overall dimensions. In classic aerodynamics, a flat plate has a CD of 1,28 while a teardrop shape could be as low as .04, Reference: NASA
The size and shape of the mirrors (as well as the rest of the car) would be reflected in the cross-section while CD reflects how slippery the object is. By the way, rotating wheels have a lower CD then stationary wheels, so even a wind tunnel test might not be accurate.
2016 SV, New battery at 45K mi.
Jamul, CA
San Diego East County

GRA
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Joined: Mon Sep 19, 2011 1:49 pm
Location: East side of San Francisco Bay

Re: Nissan Ariya to be announced for the JDM July 15, 2020

Tue Aug 04, 2020 5:13 pm

I remain of the opinion that heat pump/no heat pump can easily explain the difference in this case. I'd like C&D to test a Model Y in similar temps at the proving grounds, to see the effect vs. the Model 3.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

SueC56
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Re: Nissan Ariya to be announced for the JDM July 15, 2020

Thu Aug 06, 2020 9:42 am

@salyavin

No frunk on the Ariya. They say that they moved the air handling system forward to give more cabin space. And it's front wheel drive

The Single engine model has front wheel drive with front engine. The AWD has one front engine and one rear engine.

Sue C
Sue C
2016 Nissan LEAF SL, Coulee Red
Purchased 8/3/2019 with 9500 miles
As of 7/22/2020 it has 12k miles

cwerdna
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Re: Nissan Ariya to be announced for the JDM July 15, 2020

Wed Sep 02, 2020 1:40 am

cwerdna wrote:
Wed Jul 22, 2020 10:24 pm
Table seems to come from https://www.caranddriver.com/shopping-a ... explained/. It says they tested at 75 mph and unfortunately under varied climate conditions like the with the Model 3 around freezing temps.
Maybe we should start a new thread for this?

The Secret Adjustment Factor Tesla Uses to Get Its Big EPA Range Numbers
How Tesla puts distance between itself and the competition while still playing by the EPA's rules
https://www.caranddriver.com/features/a ... e-numbers/

(https://priuschat.com/threads/car-and-d ... tes.67235/ has some other background info about EPA mileage tests w/the C&D article written before Leaf existed.)

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Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

salyavin
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Re: Nissan Ariya to be announced for the JDM July 15, 2020

Fri Sep 11, 2020 8:10 pm


Kieran973
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Re: Nissan Ariya to be announced for the JDM July 15, 2020

Fri Sep 25, 2020 9:43 pm

Can anyone explain the 14-16 cu ft of cargo space in the specs? That's not only less than the Kona, it's on par with a sedan. What's the point of an SUV that has 14 ft of cargo space? Is this a typo? Who would have use for an SUV that can fit several large adults in the front and back seats but can't fit any of their stuff? Unless this car is being used as a taxi, or to drive around politicians whose only cargo is some folded up paper in their pockets, I literally don't see the point. Why not just put the 90 kWh battery in a sedan and then you have an E-Maxima or E-Altima with 350-400 miles of range?
2019 Leaf SV (silver) with All-Weather Package

salyavin
Posts: 189
Joined: Thu Sep 26, 2019 9:51 pm
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Leaf Number: 318726
Location: Littleton , CO

Re: Nissan Ariya to be announced for the JDM July 15, 2020

Fri Sep 25, 2020 10:02 pm

If that turns out to be true, I agree the cargo room would be too small for us and for many.

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