Aeromod nissan leaf improved aerodynamics increased range

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NeilBlanchard said:
kidjan said:
It's also worth noting that aero mods on an electric vehicle with regenerative braking should result in a bigger efficiency increase than on an ICE vehicle, because any air resistance slowing the vehicle down could have been converted into electricity. In essence, poor aerodynamics are a penalty paid twice by cars with regenerative braking.

Lower drag also means better coasting, and coasting is the best use of the kinetic energy of the moving car. Regen is great for when you need to slow down, but coasting means you accelerate less in the first place, then use it better. Regen is icing on the cake.

Understood, but when traveling over hilly terrain, or going down a mountain pass, all of that potential energy is either A) converted into kinetic energy, which is then wasted heating brakes or B) reclaimed through regen. I live in Utah; I can add 12% or more driving down little cottonwood because the road is pretty slow and steep (30 to 40 mph). But I do far less well on Parleys (I-80), because the flow of traffic is so much faster. At 60 mph or so, wind eats a lot of the regeneration I could be getting.

I could drive slower, but I'd likely be rear-ended.
 
lorenfb said:
While traveling on freeways (50% of driving) at 60 - 65 MPH in the past, my overall average was about 4.5 miles/kWh.
Presently, my freeway speeds are 50 - 52 MPH. My overall average is now 5.1 miles/kWh. That's about a 13% improvement
without any aero mods, and how simple was that!

These things aren't mutually exclusive. You can do both.
 
kidjan said:
Understood, but when traveling over hilly terrain, or going down a mountain pass, all of that potential energy is either A) converted into kinetic energy, which is then wasted heating brakes or B) reclaimed through regen. I live in Utah; I can add 12% or more driving down little cottonwood because the road is pretty slow and steep (30 to 40 mph). But I do far less well on Parleys (I-80), because the flow of traffic is so much faster. At 60 mph or so, wind eats a lot of the regeneration I could be getting.

I could drive slower, but I'd likely be rear-ended.
Two things:

Under A: you don't need to use the brakes and waste the kinetic energy. Let's say your target speed is 60mph. When coasting downhill you can accelerate to 65-70-75mph without braking, then point the nose of the car up the next hill and wait until the car decelerates back down to 60mph before adding throttle. If you have aero mods you will both gain more speed downhill and bleed less speed off as you coast uphill.

And B: regen is less efficient than just coasting, which was the original point. Regen should only be used when it's absolutely necessary to slow down, like in traffic or going into a corner, red light, etc. and even then it's best to just coast all the way to a stop (but like you said there are rear-ending risks and risks of being a jackass on the road to worry about). But to your example of I-80 downhill, with aero mods you can maintain that faster 60mph speed AND the increased regen of lower speeds because you have effectively lowered the braking force of the drag so for the same speed you can increase the braking force of regen.

Maybe that's exactly your same point haha oh well I already typed it.
 
VitaminJ said:
kidjan said:
Understood, but when traveling over hilly terrain, or going down a mountain pass, all of that potential energy is either A) converted into kinetic energy, which is then wasted heating brakes or B) reclaimed through regen. I live in Utah; I can add 12% or more driving down little cottonwood because the road is pretty slow and steep (30 to 40 mph). But I do far less well on Parleys (I-80), because the flow of traffic is so much faster. At 60 mph or so, wind eats a lot of the regeneration I could be getting.

I could drive slower, but I'd likely be rear-ended.
Two things:

Under A: you don't need to use the brakes and waste the kinetic energy. Let's say your target speed is 60mph. When coasting downhill you can accelerate to 65-70-75mph without braking, then point the nose of the car up the next hill and wait until the car decelerates back down to 60mph before adding throttle. If you have aero mods you will both gain more speed downhill and bleed less speed off as you coast uphill.

And B: regen is less efficient than just coasting, which was the original point. Regen should only be used when it's absolutely necessary to slow down, like in traffic or going into a corner, red light, etc. and even then it's best to just coast all the way to a stop (but like you said there are rear-ending risks and risks of being a jackass on the road to worry about). But to your example of I-80 downhill, with aero mods you can maintain that faster 60mph speed AND the increased regen of lower speeds because you have effectively lowered the braking force of the drag so for the same speed you can increase the braking force of regen.

Maybe that's exactly your same point haha oh well I already typed it.

Exactly - well said.

I call the technique swooping. As you get used to driving on a route, you learn to start coasting at / before the crest, so you don't go so fast on the way down to be unsafe or get a ticket; and you learn where you can carry speed to get part way up the next hill by coasting down the previous one. Another method is to use a bit of acceleration near the bottom of the hill to extend the benefit of the car's kinetic energy.

Making sure your tires are well inflated is also key. The stock Leaf Ecopia tires are very low rolling resistance, and having them inflated to 42PSI or 45 (up to the sidewall max of 51PSI) will help lower rolling drag, and this lowers the consumption, and raises the range.
 
Understood, but for mountain passes, "swooping" doesn't apply. That's my point--you grind battery on the way up, regen on the way down. The only thing that helps is less wind resistance on the way up, and less on the way down to increase the amount of regen that can happen.

I'm really not talking about "coasting" at all. Agreed regen isn't beneficial there.
 
The regen vs. coasting isn't as easy as this is better than that.

If you were to go down a long straight slope with no speed limit simply coasting wouldn't be the most efficient choice. Basically the car would speed up until the force of gravity on the car is equal to the force of aerodynamic drag and rolling resistance. At that point you wouldn't be using any electric energy, but you wouldn't be gaining any either. Once at the bottom the car would have a lot of kinetic energy that you could still use to coast on for a while more. But that would be about it.

On the other hand, let's say you regen and keep you speed down low most of the hill. You would have a lot less air drag, so a lot more energy would be being converted back into electrical energy. Now regen isn't the greatest. But at least you'd be getting something back. As you near the bottom, however, it wouldn't make much sense to regen right down to the bottom and then switch right back to electric propulsion. Instead, at a certain point closet to the bottom the car could be "shifted" into neutral and you could build up momentum. Air drag would increase, but it would only be momentarily, not the whole mountain. You could build up quite a bit of momentum then and have enough to keep coasting after the long down hill slope.

Monarch pass is a perfect example of where this would work. Clear from the top down the whole pass has a speed limit of 45mph with corners as slow as 25mph. Most trucks don't do over 35mph. You could put it in B mode and use the cruise to maintain 25 to 35mph down nearly most of the whole mountain. Near the bottom the speed limit changes to 65mph. At that point you can easily "shift" into neutral and coast up to 65mph or more. I bet in that small section you could hit over 80mph if you tried by just coasting. But if it were possible to coast clear from the top (which it isn't because of the curves) I doubt you'd get much more than 80mph because by that point you'd nearly have more air drag than gravity.
 
I'm really unclear what point you're trying to make. The bottom line is wind resistance is wasted energy that could have been put into regen in many instances--for example going down a long mountain pass--hence the thread on improving aerodynamics.
 
kidjan said:
I'm really unclear what point you're trying to make. The bottom line is wind resistance is wasted energy that could have been put into regen in many instances--for example going down a long mountain pass--hence the thread on improving aerodynamics.
That there are times when it's better to regen brake and go slow down a hill, and times when it is better to shift into neutral and let the vehicle speed up. It's not a "this is always better than that" situation. On a long slope it's best to regen brake from the top down most of the way. But if you're close to the bottom, the amount of energy you would get from regen braking would be less than the kinetic momentum you could build up by coasting.
 
I understand your point now.

Still, we're talking about aerodynamic efficiency. If I'm going down parleys canyon (roughly twelve miles of travel, ~2500 feet drop) the optimization you're describing isn't noteworthy. 11.5 miles of regen is going to dwarf what you're talking about. And aerodynamic improvements will help both the coasting and regen scenarios, for that matter.

If we're talking about hilly midwestern terrain with 100 ft climbs here and there, sure. But in a state like Utah, where 500 ft of elevation gain is normal (I do something close to that just dropping my kid off at school), optimizing aero to improve regen is a lot more interesting.
 
Also, what I'm talking about is completely observable if I compare Little Cottonwood Canyon with Parleys.

Parleys is on I-80; speed limit is 70 mph. Speeds under 55 are unsafe. As a consequence of this, it's hard to maintain a safe driving speed and have significant regen because so much is wasted to aerodynamic losses. I usually take the car out of eco, put it in P to try and compromise between maintaining a safe speed but still having some regeneration. I usually regenerate a 3-5% of my battery over the 12 mile stretch.

In Little Cottonwood, however, 30-40 mph the entire way is completely feasible. I've regenerated 10-14% of my battery on the way down. Little cottonwood has slightly more elevation than parleys, so that's one factor, but it isn't enough of a factor to justify 3-4x the regen.

In parleys, regen is simply getting eaten by aero losses.
 
The overall energy use is the point - coasting whenever possible is the best way to move the car using less energy.

If you don't waste energy getting the car moving, and you coast when possible, and use regen only when you need to slow the car down.

Aero drag is always a total loss, and that is why lowering the drag with modifications always saves energy. Using regen doesn't change the energy lost to drag.
 
Coasting is not the correct answer when you have a huge amount of potential energy available to you in the form of elevation gain. Tell you what: let's do an experiment. You coast down parleys, and I'll regen down parleys, and we'll see who ends up with more battery at the bottom.
 
Also, "Using regen doesn't change the energy lost to drag" is _not_ my argument. That's your argument. My argument is you can get more out of regen by improving aero. That's always been my argument.
 
Yes, improving aerodynamic shape and size will help improve efficiencies both coasting and regenerating. But the shape of the vehicle isn't the only factor that affects air drag. So does speed, for an example.

We're looking for the best overall efficiency and energy savings. Last week I did a 180 mile trip that had an 11,000ft climb and descent. Coasting down hills for several thousand feet would not have been safe, practical, nor the most efficient regardless of the aerodynamic shape modifications made to the vehicle. Nor would regenerating clear to the bottom have been the most efficient either. Since driving habits directly affect aerodynamic drag you can't talk about improving aerodynamics and not discuss driving habits and techniques.
 
IssacZachary said:
Since driving habits directly affect aerodynamic drag

back to your armchair, time to do some googeling....

point blank aerodynamics conserves energy. as does driving technique. I have driven from castle rock washington to the mt saint helens observatory in my aeromodded nissan leaf; a distance of 55 miles and a climb of 7000' to arrive with zero battery. Then pointed my nose downhill and completed the return trip home. For a total travel distance of 110 miles including significant hills in Ruby our aeromodded 2012 nissan leaf!

Fully loaded with occupants, scopes and cameras for each...

The keys to the success of this trip to see the lunar eclipse across mnt saint hellens. was on the way up we kept the speed below 50 mph, on the way down regen anytime the speed exceed 45 mph, otherwise coast down to as low as 40 then use cruize controll to hold 40 up the next bump...

A subtle additional point of improved aerodynamics is reduced wear on the SOH of the battery. As less energy is needed to maintain any given speed, and more kenetic energy is preserved, the discharge is of a lower C rate, or wattage/capacity and recharges are for a lower KWH for any given travel distance.

I got my +++ tripple win plusses, go get you some....
 
IssacZachary said:
Since driving habits directly affect aerodynamic drag you can't talk about improving aerodynamics and not discuss driving habits and techniques.

Sure you can. We can all acknowledge faster = more drag = less efficient, and that's about all there is to talk about. It really isn't relevant to a thread about improving the car's aerodynamics.
 
kidjan said:
IssacZachary said:
Since driving habits directly affect aerodynamic drag you can't talk about improving aerodynamics and not discuss driving habits and techniques.

Sure you can. We can all acknowledge faster = more drag = less efficient, and that's about all there is to talk about. It really isn't relevant to a thread about improving the car's aerodynamics.

Well then people (me too) shouldn't be talking about how to go down hills here then either. And IMO the title "improving aerodynamics" should be changed to "improving aerodynamic shape" since that seems to be what people actually mean. Aerodynamic shape is only one part of aerodynamics. Driving when it's warmer, like during the day or when the barometric pressure is low will improve aerodynamics too. So will driving in higher altitude, or on the Moon. Driving slower improves aerodynamics. There's the practicality of a body modification that can come into question when one driver has 25mph speed limits and the other goes 85mph. Driving down a hill now causes a situation where a gain in energy from one area causes a loss in another area. But if that's all irrelevant then let's forget it all and move on. I agree that it is a bit much for one thread on aerodynamics so I apologize.
 
I'm really not trying to talk about going down hills--I never was, and I'm really unclear why people are talking about driving technique in this thread at all. My only point: aerodynamic efficiency impacts regen, and I suspect much more than people realize.
 
kidjan, I apologize for kicking it off. Everyone is agreeing with eachother very sternly. Everyone is pretty much saying the same thing.

In aeromod news:
I was used car shopping with my dad and noticed a lot of the newer hybrids and econo cars have vortex generators around their sideview mirrors, on the roof, tail lights, and other places. I am curious about using some turbulator tape around the mirrors. Basically the idea is to reduce the flow separation on the abrupt angle on the rear side of the mirrors.

Also I got one of those really cheap shark fin antenna covers, but I'm just going to gut it and put the element inside a more teardrop shaped bubble.

Some people might laugh but every little bit counts! I remember back in my racing days people would remove the side mirrors and use little tiny convex mirrors inside the window instead. Also without the front air dam, which was only 1.5" tall, you would lose a car length or two on the straights. Those were 110hp cars and it made a big difference.
 
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