Titanium48
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 12:45 pm

LeftieBiker wrote:The most efficient speed is something like 17MPH. That being said, 55MPH is definitely better than 65MPH, and 40-45MPH works well on secondary roads . Since the indicated speed is 2MPH high, I usually set (on my old 24kwh Leaf) the cruise control to 57MPH, and let it drop to 50 on uphills. The bottom line: if you need to extend range, go as slowly as traffic safely allows.
The most efficient speed is assuming no accessory power use, and there isn't a lot of change between the most efficient speed and about 50-60 km/h (30-35 MPH). If you are using heat or AC, the top end of that range can be more efficient because you get where you are going faster and use less energy for climate control. Beyond about 60 km/h the drop in efficiency with increasing speed becomes noticeable, and continues to get worse the faster you go.
LeftieBiker wrote:If you have to go fast, try getting 4 car lengths behind a tractor-trailer, matching speeds, and drafting it. That isn't extremely safe, however...
Will adaptive cruise control on the newer models allow you to get you close enough to make a difference with less reliance on the driver's reaction time?

Titanium48
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 12:54 pm

powersurge wrote:So what people are saying is that if the speed limit is 65, then everyone needs to do this speed (or more)?
Speed differentials are the biggest speed-related traffic hazard, so while people shouldn't drive over the speed limit, it isn't a good idea to go much slower either, unless road conditions are poor.

It really doesn't help that most freeways in North America were designed for speeds of 130 km/h (85 MPH). Enforcing limits much below that will always be problematic because it just feels too slow to most drivers. A lot of money could have been saved over the years by using a slower design speed, which would have allowed narrower lanes, shorter merge and exit lanes, sharper corners and steeper hills. Those features would have also cued drivers to slow down, and enforcing slower, more efficient speed limits would have a lot more support.

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Nubo
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 4:36 pm

powersurge wrote:So what people are saying is that if the speed limit is 65, then everyone needs to do this speed (or more)? ...
That is the standard interpretation of speed limits by American drivers. I.e., "At LEAST drive the speed limit! What are you, crazy?" :lol:
I noticed you're still working with polymers.

DougWantsALeaf
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 5:41 pm

In my gen 1 (2013), agreed that best to not stay above 55 unless I’m a steep downhill section, and let it drift to 50mph on inclines.

Enjoy the right lane.

Keep tires at 40psi or a bit more as you feel that small hike in range from 35psi.


Watch for thick pockets of traffic to maintain momentum. It’s better to glide in neutral then to regen if continuing on the highway. Get used to the quick wrist manuver of flipping the car out of drive. Would stay away from b mode on highway as it’s too easy for regen to kick in.
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2013 Leaf SV
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Max distance on 13 Leaf: 120 miles
Max distance on 19 Leaf: 242 Highway 4.5 miles/kWh (4.9 KWh remaining)

LeftieBiker
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Re: Most Efficient Freeway Speed...Is There One?

Wed May 01, 2019 6:12 pm

Will adaptive cruise control on the newer models allow you to get you close enough to make a difference with less reliance on the driver's reaction time?
Yes, approximately. The default setting of an alleged 3 car lengths may be too long (it's more like 5 or 6), but you can change it to two or one car lengths (which is actually about 3-4 small car lengths). The way that Pro Pilot ACC reacts, though, is less than ideal. It will wait a bit too long, brake HARD, and then, when the way is clear, it accelerates too slowly. I wouldn't want to rely on it alone if drafting a truck.
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PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

DougWantsALeaf
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Re: Most Efficient Freeway Speed...Is There One?

Tue May 21, 2019 8:53 am

I have noticed that many of the review sites are quoting Leaf+ performance at 70 MPH. Efficiency only in the mid 3's of miles per kWh. While that may be typical for many consumers, I would like an "economist" of EV drivers site to show the more thrifty range/efficiency for different evs. I am guessing the different cars perform quite differently at different speeds in terms of relative efficiency.
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Max distance on 13 Leaf: 120 miles
Max distance on 19 Leaf: 242 Highway 4.5 miles/kWh (4.9 KWh remaining)

SageBrush
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Re: Most Efficient Freeway Speed...Is There One?

Tue May 21, 2019 10:17 am

DougWantsALeaf wrote:I have noticed that many of the review sites are quoting Leaf+ performance at 70 MPH. Efficiency only in the mid 3's of miles per kWh. While that may be typical for many consumers, I would like an "economist" of EV drivers site to show the more thrifty range/efficiency for different evs. I am guessing the different cars perform quite differently at different speeds in terms of relative efficiency.
I'm not sure what you mean but Aero drag is proportional to CdA and to the square of velocity. This means that if you take two cars and set them to the same speed on the same road (to have the same air density) the drag will vary by their relative CdA values. Different speeds will not change CdA(1)/CdA(2)
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
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2018 Tesla Model 3 LR, Delivered 6/2018

powersurge
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Re: Most Efficient Freeway Speed...Is There One?

Tue May 21, 2019 11:58 am

OMG now we are debating drag coefficients!!

The original question was is there a best speed for efficiency.... I say..... Keep it between 50 and 60...

SageBrush
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Re: Most Efficient Freeway Speed...Is There One?

Tue May 21, 2019 12:12 pm

BeachLeaf wrote: That is, is there a notable difference from going 55 MPH vs. 65 MPH when considering distance?
Mark
~ 20%. Is that 'notable' ?:

Aero drag is 0.5 * Rho * Cd * A * v * v

For the 24 kWh LEAF,
CdA * Rho * 0.5 = 0.725 * 0.6125 = 0.44

Air drag at each speed:
55 mph = 24.6 m/s. At 55 mph there are 24.6 * 24.6 * 0.44 = 266 Newtons of air drag
65 mph = 29 m/s. At 65 mph there are 29 * 29 *0.44 = 370 Newtons of air drag

--> 370 - 266 = 104 Newtons difference. Over one km that is 104*1000 = 104k joules/km = 29 Wh/km. Or 46 Wh/mile.
Or perhaps more useful, 4.6 kWh more energy to the wheels per 100 miles. That would be ~ 4.6/0.87 = 5.3 kWh more battery energy
Last edited by SageBrush on Wed May 22, 2019 7:27 am, edited 7 times in total.
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Two years in Colorado, now in NM
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

webeleafowners
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Re: Most Efficient Freeway Speed...Is There One?

Tue May 21, 2019 12:40 pm

DougWantsALeaf wrote:I have noticed that many of the review sites are quoting Leaf+ performance at 70 MPH. Efficiency only in the mid 3's of miles per kWh. While that may be typical for many consumers, I would like an "economist" of EV drivers site to show the more thrifty range/efficiency for different evs. I am guessing the different cars perform quite differently at different speeds in terms of relative efficiency.
Yah. 70 mph is somewhere around 115 kmh. Few and far between in this province. Most places it’s 90 or 100 kmh.
2015 Smart Electric Drive convertible.
2016 Nissan Leaf SV 30KWh
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