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Transition B to D mode speed change?

1942 Views 17 Replies 9 Participants Last post by Huey52, Sep 30, 2021

VW Dave

Discussion Starter · Sep 28, 2021

I searched and couldn’t find mention of this. Apologies in advance if it’s covered.

Scenario: Driving on flat pavement at a constant speed. I turned B mode on for doing hills to get out of my neighborhood. So now I’m in the flats and turn B off.

Invariably and with 100% repeatability, within a couple seconds of turning B off, the car starts to speed up on its own. I am not changing accelerator position or anything else. Car starts speeding up until I back of the accelerator.

Two e-Golfs didn’t do this. Audi Q5e didn’t do this. ID.4 does it every time.

in fact I can be climbing a hill in B mode. Turn it off while climbing and car wants to speed up.

Anyone noticed this? And respectfully please don’t tell me I must be “doing it wrong”. The car is accelerating moderately without driver input. It’s a little unnerving the first few times it happens.

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Huey52

· #2 · Sep 28, 2021

Mine does that as well Dave. It's the normal B regen releasing which in effect in D "freewheeling" speeds up. You'll learn to let off the accelerator a bit when you transition B->D as a result. Yes, unnerving until you realize what it's doing and compensate for same.
I too use B around town and then switch to D on the highway. However if highway "accordion" slowdowns are encountered I just leave it in B for the more assured innate regen braking.

Related: as we know VW implemented "D" mode the way they did so new BEV drivers would feel more like they were in an ICE vehicle. It's "B" mode that is the alien one.

VW Dave said:
I searched and couldn’t find mention of this. Apologies in advance if it’s covered.

Scenario: Driving on flat pavement at a constant speed. I turned B mode on for doing hills to get out of my neighborhood. So now I’m in the flats and turn B off.

Invariably and with 100% repeatability, within a couple seconds of turning B off, the car starts to speed up on its own. I am not changing accelerator position or anything else. Car starts speeding up until I back of the accelerator.

Two e-Golfs didn’t do this. Audi Q5e didn’t do this. ID.4 does it every time.

in fact I can be climbing a hill in B mode. Turn it off while climbing and car wants to speed up.

Anyone noticed this? And respectfully please don’t tell me I must be “doing it wrong”. The car is accelerating moderately without driver input. It’s a little unnerving the first few times it happens.

Nai3t

· #3 · Sep 28, 2021

Don't think of the accelerator pedal as any sort of fixed, direct, or proportional relationship to the motor output.

The throttle is mapped to achieve a certain feel. Similarly, if your change between modes (Sport to Eco) you'll notice the same. Try it.

Since they can't change spring rates or travel in the pedal, they quite effectively make these adjustments to driver perception through remapping.

Reactions: 1

Huey52

· #4 · Sep 28, 2021

Same for VW AG sporty ICE vehicles. In this "drive-by-wire" era it's all mapping. Hence the significant ICE throttle response differences between mode selections Sport-Dynamic-Comfort-Eco. It's a brave new world.

Nai3t said:
Don't think of the accelerator pedal as any sort of fixed, direct, or proportional relationship to the motor output.

The throttle is mapped to achieve a certain feel. Similarly, if your change between modes (Sport to Eco) you'll notice the same. Try it.

Since they can't change spring rates or travel in the pedal, they quite effectively make these adjustments to driver perception through remapping.

Reactions: 1

VW Dave

Discussion Starter · #5 · Sep 28, 2021

I hear and understand everything y'all are saying. I am not convinced that this behavior is intended. A car should never arbitrarily accelerate faster unless the driver has asked the car to do that by pushing down on the pedal.

That's my story and I'm sticking to it. Please keep in mind my experience with the e-Golf. Or maybe for some reason they've thrown that model of behavior out the window.

Huey52

· #6 · Sep 28, 2021

But you are de facto pushing down [more] on the pedal [than the computer expects] given the sudden mode change.

Recommend you leave yours in just one mode. "You can't handle the truth."

When it becomes self aware it will no longer care about the human input anyway.

VW Dave said:
I hear and understand everything y'all are saying. I am not convinced that this behavior is intended. A car should never arbitrarily accelerate faster unless the driver has asked the car to do that by pushing down on the pedal.

That's my story and I'm sticking to it. Please keep in mind my experience with the e-Golf. Or maybe for some reason they've thrown that model of behavior out the window.

VW Dave

Discussion Starter · #7 · Sep 28, 2021 (Edited)

Huey52 said:
But you are de facto pushing down [more] on the pedal [than the computer expects] given the sudden mode change.

When it becomes self aware it will no longer care about the human input anyway.

Well another explanation could be the software is compensating incorrectly for an event not involving the driver asking for faster acceleration.

There’s an old thread here somewhere something like “Don’s car unintended acceleration”. Wonder if ‘ol Don happened to switch from B to D at the time. This isn’t unintended acceleration because it’s not uncontrolled. It is unexpected though.

Edit: That is, when the car is in manual driving mode. Of course if you’re using Travel Assist and its related features, the car will have more of a say in these things.

I’ll try different driving modes and see what happens.

Nai3t

· #8 · Sep 28, 2021

In my i3 when I charge from regular mode to Eco, if I'm on the highway and don't do anything with my foot, the car slows so aggressively it could probably cause an accident if somebody is following too closely.

And that's the intent: if I want to go fast in Eco mode, they want me to really have to mash down past the sweet spot on the pedal.

I'm sure with the ID.4 the intent is to make the car feel "freer" in D and more rubber-bandy constrained in B.

In either case, the expectation is the driver adapts by adjusting foot position.

Reactions: 1

AWD Or Nothing

· #9 · Sep 28, 2021

What happens when you transition from flat to a down hill and you don't move the pedal position? Does the car get faster by surprise? The pedal configures acceleration, not speed. So is it reasonable to expect constant speed, or constant acceleration?

If other factors change, eg road slope and surface, wind direction, etc, then you automatically adjust the pedal position to compensate.

What if you were in an ICE car, and switched from "D" to another gear (eg. overdrive gear), would you hold the accelerator in the exact same position and expect no speed change? Or do you have intuition about the engine gear ratios, and know the expected outcome and compensate by moving the accelerator pedal?

So why does the drive mode change from 'B' to 'D' not get the same treatment?

Probably because the drive mode change effect is a bit opaque -- you truly don't know how it affects different systems; and you have better intuition from experience on the other more relatable factors based on natural phenomena (like gravity and friction).

As long as drive mode does not change by itself, I don't think it's fair to call it unintended -- or even unexpected --acceleration. The "B" mode is a made-up thing by people, not a natural phenomena that we can easily relate to. Just need to learn the mapping of the accelerator to the different modes. You will learn to expect it and compensate.

In other words, it's not a bug, it's a user training issue.

I know that sounds lame, everything should be intuitive to the user-- and this behavior isn't necessarily intuitive, so there probably is room for improvement, but I can't easily fault VW for this.

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Spin

· #10 · Sep 28, 2021

VW Dave said:
There’s an old thread here somewhere something like “Don’s car unintended acceleration”. Wonder if ‘ol Don happened to switch from B to D at the time.

Don was not switching modes when he experienced this.

Huey52

· #11 · Sep 29, 2021

Are we sure? Ol' Don has a tendency to fill us in on details a bit like an Ol' episodic novel. "Oh yeah, forgot to mention ...."

[as a fellow elder I can get away with same 🤪]

Spin said:
Don was not switching modes when he experienced this.

Spin

· #12 · Sep 29, 2021

Huey52 said:
Are we sure? Ol' Don has a tendency to fill us in on details a bit like an Ol' episodic novel. "Oh yeah, forgot to mention ...."
[as a fellow elder I can get away with same 🤪]

Yes. He was driving very slowly in his retirement community.

Reactions: 1

JPWhite

· #13 · Sep 29, 2021

VW Dave said:
I searched and couldn’t find mention of this. Apologies in advance if it’s covered.

Scenario: Driving on flat pavement at a constant speed. I turned B mode on for doing hills to get out of my neighborhood. So now I’m in the flats and turn B off.

Invariably and with 100% repeatability, within a couple seconds of turning B off, the car starts to speed up on its own. I am not changing accelerator position or anything else. Car starts speeding up until I back of the accelerator.

Two e-Golfs didn’t do this. Audi Q5e didn’t do this. ID.4 does it every time.

in fact I can be climbing a hill in B mode. Turn it off while climbing and car wants to speed up.

Anyone noticed this? And respectfully please don’t tell me I must be “doing it wrong”. The car is accelerating moderately without driver input. It’s a little unnerving the first few times it happens.

I'd bet that what your experiencing is a different accelerator mapping between the two modes. Our LEAF does the same. Between the two modes the same position on the accelerator is mapped to different % of acceleration input.

My preference is to leave the car in B mode all the time. And sport mode as well of course ;-)

Reactions: 1

Spin

· #14 · Sep 29, 2021

VW Dave said:
I searched and couldn’t find mention of this. Apologies in advance if it’s covered.

Scenario: Driving on flat pavement at a constant speed. I turned B mode on for doing hills to get out of my neighborhood. So now I’m in the flats and turn B off.

Invariably and with 100% repeatability, within a couple seconds of turning B off, the car starts to speed up on its own. I am not changing accelerator position or anything else. Car starts speeding up until I back of the accelerator.

Two e-Golfs didn’t do this. Audi Q5e didn’t do this. ID.4 does it every time.

in fact I can be climbing a hill in B mode. Turn it off while climbing and car wants to speed up.

Anyone noticed this? And respectfully please don’t tell me I must be “doing it wrong”. The car is accelerating moderately without driver input. It’s a little unnerving the first few times it happens.

As someone that constantly changes modes, I never noticed this. Since I found out that the brake lights come on when releasing the accelerator completely in B mode, I drive in D and use B mode as a brake. I had to take the car for a ride this morning to try to recreate this phenomenon, and yes, my car does accelerate as well. I guess I just subconsciously adjusted for this with my foot. I don't see this as a problem. I see this as part of the activity known as "driving".

Reactions: 1

Enzo589

· #15 · Sep 29, 2021

JPWhite said:
I'd bet that what your experiencing is a different accelerator mapping between the two modes. Our LEAF does the same. Between the two modes the same position on the accelerator is mapped to different % of acceleration input.

My preference is to leave the car in B mode all the time. And sport mode as well of course ;-)

I have noticed this as well. I think that it is because the position of the accelerator in B and D may not be equal as far as how it translates to how much the car should accelerate based on the position of the pedal. I’ve gotten used to it and when switching from B to D, I know to then lift my foot slightly to make it a smooth transition.

Reactions: 2

terasain

· #16 · Sep 30, 2021

how do you change from B to D, when i am in B and i twist back, it goes to N. D to B works.

John411iD

· #17 · Sep 30, 2021

terasain said:
how do you change from B to D, when i am in B and i twist back, it goes to N. D to B works.

Turn forward to B again, it will change to D.

Reactions: 2

Huey52

· #18 · Sep 30, 2021

I take it you select a mode upon startup and leave it as is for the duration of your trip.
I empathize that the Owner's Manual is not the easiest to read, but you really should try to get through it once. And heck, you've been a member here for 11 months now.

Note last paragraph:

Font Screenshot Motor vehicle Advertising Multimedia

terasain said:
how do you change from B to D, when i am in B and i twist back, it goes to N. D to B works.

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