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2021 ID.4 First Edition / Dusk Blue
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Discussion Starter · #1 ·
It's been my understanding that the best place to take advantage of 'D' mode is on highways, where there can be substantial benefit from gliding. Similarly, regenerative 'B' mode is best for local traffic, especially stop and go.

I've recently begun to follow the infotainment data (especially miles/kWh) and was surprised that I'm getting better performance with 'D' in both environments. I live in a city, and pretty much every corner has a stop sign: in 'B' mode, I'm getting 2-2.4 (mind you, I'm never doing a fast start from stop, and rarely exceeding 30)! However, in 'D' mode this stop and go traffic gets me 2.8-3.2 -- still nothing to be pleased with, but consistently better.

I'm wondering how accurate this infotainment data is -- maybe I'm just getting bad data? But I'm also a bit concerned that I'll do a series of 5 mile trips, and each one takes off 7-10.

Now I know that these are guess-o-meter (GOM) estimates, but they never fall the other way (that is, drive 10 miles and only lose 5 miles). What advice do folks have for measuring performance more accurately, and optimizing the use of B and D modes?
 

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ID.4 Pro S Gradient AWD pre-ordered 9/23/2020
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It’s a myth that regen braking is more efficient than coasting. You want to use the car’s kinetic energy to maintain as much momentum as possible. If you’re constantly slowing down, you’re also constantly accelerating to recover the lost speed. It takes more energy to accelerate than can be recovered via regeneration.
 

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From reports so far the infotainment data is very accurate. According to VW - D is designed to be more efficient and it makes sense:
Here is a good article about Brake or coast? Intelligent regenerative braking on the Volkswagen ID.4
The amount of benefit of D will vary depending on how much you use coasting, and how much the system learns your route and observes the other cars and then applys its smart regen just where needed, instead of every time you take your foot off the pedal that you get with B mode.
 
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ID.4 1st Edition
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I agree. Historically I've never liked paying twice for momentum.

However around town I simply like the "auto-braking" of 'B' mode. I've gotten so used to it in just over a month that when I drive my wife's SUV I have to consciously tell myself to brake earlier.
So for me I really don't care if there's actually a performance hit. Like appetites, there's always another nightly charge opportunity coming along. ;) [~credit Seinfeld]
It’s a myth that regen braking is more efficient than coasting. You want to use the car’s kinetic energy to maintain as much momentum as possible. If you’re constantly slowing down, you’re also constantly accelerating to recover the lost speed. It takes more energy to accelerate than can be recovered via regeneration.
 

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2021 ID.4 First Edition / Dusk Blue
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Discussion Starter · #5 ·
From reports so far the infotainment data is very accurate. According to VW - D is designed to be more efficient and it makes sense:
Here is a good article about Brake or coast? Intelligent regenerative braking on the Volkswagen ID.4
The amount of benefit of D will vary depending on how much you use coasting, and how much the system learns your route and observes the other cars and then applys its smart regen just where needed, instead of every time you take your foot off the pedal that you get with B mode.
I've never before considered driving mode to be a philosophical decision 😆 but thanks for sharing the article!
 

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I think it's extremely noticeable on a downhill, B will get you back everything you lost going up a mountain and more as I experienced first hand. But as others have said, if you are accelerating from a stop a lot the gains are minimal.
 

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I personally only plan on using “B” mode for mountain driving or on winding roads where you can use the motor to decelerate quickly. It can definitely be a benefit on the downhills. When I ultimately go back to the office I’ll test which mode I like better for my commute, but I think even in stop and go D mode is ultimately better. If it was true one-pedal driving, though, it might be a different story, but until they add that as a feature I’m ok with D.
 

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ID.4 FE
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In D mode you get the benefits of both coasting and regen. If you're brake gently enough with the pedal it's using regen for the braking power until you hit a certain g amount, at which point the physical brakes kick in. B mode gives you the more aggressive regen braking just letting off the accelerator, but in doing so you lose the coasting. Ask any hypermiler how important coasting is to maximizing fuel economy.
 

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2017 Chevrolet Bolt, 1994 Nissan 300ZX
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I think it's extremely noticeable on a downhill, B will get you back everything you lost going up a mountain and more as I experienced first hand. But as others have said, if you are accelerating from a stop a lot the gains are minimal.
I don't think you really got back more than you used going up a mountain (possibly the Guess-o-meter thinks so) since then VW would have created the first perpetual motion machine. ;)
 

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ID.4 1st Glacier White w/Lunar Gray - order 9/23
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I think you get more going down because its always further going down the hill than going up (Grandpa told us that so it must be true)
 
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Cruise control is more efficient than coasting, coasting is more efficient than regen, and regen is more efficient than friction brakes. But comparing coasting with regen is a category error. Coasting won't bring you to a stop in a reasonable amount of time.

The benefit of a full-strength B-Mode (Which the ID.4 doesn't have) is you can learn how much space you need to stop using regen only, and maximize your regeneration when you do actually need to stop. The way I drive involves very little true coasting. It also gives me one pedal for all of the motor functions, and the other pedal for all of the friction brake functions. If I need to maintain constant speed on a highway, I turn on cruise control (and CC will manage speed efficiently). If I need to stop frequently, I want to maximize regen - and thus I want to have all the regen available to me in B-Mode.

In D I have to guess whether I'm braking too much for regen and engaging friction brakes.
In B, I can brake completely on regen. If I want to coast for a short period I can feather the pedal to a neutral position quite easily.

In the end, both methods can be quite efficient, especially with smart software (and sometimes, D mode is way safer, like when the roads are frozen). I want the option to use either mode, depending on how I want to drive for the day. I absolutely want B-mode to have the option of giving me full regen. And I absolutely think creep should be able to be disabled in any mode.
 

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ID.4 1st Edition White / Lunar Grey
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Cruise control is more efficient than coasting...
I think this is debatable as a blanket statement.

The ID.4 cruise is pretty smooth, but let's talk in generalities.

Cruise can't sense merging vehicles like a human can and open a gap. It can approach a slow moving vehicle too rapidly then have to bleed speed quickly. It can sense an open gap then accelerate into it too quickly to get back to target speed. It can't see approaching inclines although this is more of a problem driving ICE, not as affected with instant torque EVs.

My point being a driver who is "on point" can probably easily "out-efficient" cruise control. But there are a lot of drivers who aren't driving with the constant attention necessary, and there's also variability in ACC systems.

I just think it's hard to make that generalization.
 

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I think this is debatable as a blanket statement.
That's fair. ID.4's adaptive cruise is not as good as others I've seen (and way worse than OpenPilot) at handling the car in front either cutting in or changing lanes away. It often brakes unnecessarily, and not as smoothly. It's especially bad when the lead car changes lanes into a turn lane and slows down. I hope they improve this with OTA.

My intention with that statement is that for pure purposes of maintaining speed on the freeway it's better to set cruise and let it maintain a constant speed than to 'pump-and-coast', as was often the ideal method used by Hybrid ICE hypermilers. That method took advantage of the very narrow peak efficiency band of the ICE to get as much energy out of the engine as possible, then riding it until needed again. For an electric motor lower power draw is generally more efficient (less heat losses, less EM eddying), so constant low power draw is more efficient for a BEV.
 

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Driving in D mode, the car seems to do more than just coast. It feels like it’s maintaining momentum (without cruise control on). Maybe that’s the low drag coefficient I’m feeling. It’s very impressive.

What really bugs me is when I come to a stop at an incline using minimal pressure on the brake pedal, after a few seconds holding the brake at that same pressure I used to come to a complete stop, the car starts to roll back. I then have to quickly slam on the brake pedal to stop. I thought this car has an anti-roll feature. Why do I have to press the pedal harder than is required to come to a complete stop in order to avoid rolling?
 

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ID.4 Pro S Gradient AWD pre-ordered 9/23/2020
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Driving in D mode, the car seems to do more than just coast. It feels like it’s maintaining momentum (without cruise control on). Maybe that’s the low drag coefficient I’m feeling. It’s very impressive.

What really bugs me is when I come to a stop at an incline using minimal pressure on the brake pedal, after a few seconds holding the brake at that same pressure I used to come to a complete stop, the car starts to roll back. I then have to quickly slam on the brake pedal to stop. I thought this car has an anti-roll feature. Why do I have to press the pedal harder than is required to come to a complete stop in order to avoid rolling?
It has hill hold, but that will only prevent the car from rolling for a short period of time and then the brakes release. This is similar to how hill hold works in most cars. What you’re experiencing is that it takes less braking force to stop the vehicle when you’re driving up hill (even a slight incline), so it take less force to stop the car than it does to hold the car still because gravity is helping you stop the car. I experience the same thing in MINI which is a manual transmission.
 

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I have 3, actually 4, hill holds on my i3.

If I roll to a stop on an incline (no brake), the electronics will create enough resistance in the drive motor that the car holds, won't roll back. "Ready" appears on the driver's display to indicate the car is in gear. This state consumes electricity.

If I step on the brake, this engages the hydraulic brakes and releases the electric hold mentioned above. But when I release the brake pedal, an inclination sensor registers I'm susceptible to rolling back, and electrically engages a solenoid that locks brake pressure while my foot transitions from the brake pedal and onto the accelerator. This solenoid holds for about 1 second; at that point, it releases, and the vehicle begins to roll back before the motor catches it. It won't continue to roll backward.

Lastly, I can set the parking brake, just like most gas cars with electric parking brakes. The parking brake will remain engaged and hold the car until I press on the accelerator, at which point it will automatically release.
 

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ID.4 Pro S Gradient AWD pre-ordered 9/23/2020
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I always found it fascinating with my i3, on a steep hill you can actually see the power meter showing energy usage if you left your foot off the brake after the hill hold shut off.
 
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