Speed up on small hops?

[epirali]

Sorry if this has been discussed before but I have now noticed a couple of times that if I am going over a small bump or a drop in the road when the car suspension lifts a little bit the car has a sudden short burst acceleration. It stops as soon as the weight settles back down.

Anyone else notice this?

 

[I33t]

Nope.

 

[alohart]

If you were decelerating when you hit the bump, it's likely that traction control turned off the regen until the wheels were back on the ground and obviously not skidding. Having strong regen momentarily turn off could feel like a sudden acceleration.

 

[stumbledotcom]

Yes, I noticed the behavior change after the update that reduced the brake regen level in general. I believe multiple, severe bumps now causes the regen to cut out completely. Part of the effort to make it "easier" for the average, inattentive driver. Many poorly-trained drivers unconsciously lift off the accelerator when hitting rough pavement. They're used to the coasting action of a typical ICE car. With the i3's original behavior, brake regen would cause a significant slow down. Now the regen momentarily drops completely so the car coasts over rough pavement. The action probably isn't noticeable to most on level streets.

But there's one situation in particular where this change is for the worse. Driving down an incline, decelerating as you approach a full stop intersection. If you cross a rough patch just before the stop, the car will suddenly surge forward as the regen cuts out. The only solution is to jump on the friction brake. I hit several of these scenarios each day here in San Francisco since we have plenty of significant hills, badly broken/patched pavement, and a stop sign or traffic light nearly every block. This programming change has made the i3's driving dynamics unpredictable and one-pedal driving more difficult for me.

I complained to the BMW i Genius line a few days after having the updates applied to my car. They claimed their software release notes didn't include a reference to brake regen changes so they'd consult with the engineers and get back to me. Never heard anything else of course.

 

[epirali]

If you were decelerating when you hit the bump, it's likely that traction control turned off the regen until the wheels were back on the ground and obviously not skidding. Having strong regen momentarily turn off could feel like a sudden acceleration.

Thanks, I have noticed that, and I kind of expect that because almost all electric cars I own do a version of that. The Leaf was the worse by far. But this was when I was applying very light power to essentially keep speed stable. It was more like the reduction of force needed on the car from lift was not compensated for for around 500 ms. It wasn't dangerous because it didn't last long enough (unless you were just stupidly on someones tail), just kind of jarring.

 

[epirali]

Yes, I noticed the behavior change after the update that reduced the brake regen level in general. I believe multiple, severe bumps now causes the regen to cut out completely. Part of the effort to make it "easier" for the average, inattentive driver. Many poorly-trained drivers unconsciously lift off the accelerator when hitting rough pavement. They're used to the coasting action of a typical ICE car. With the i3's original behavior, brake regen would cause a significant slow down. Now the regen momentarily drops completely so the car coasts over rough pavement. The action probably isn't noticeable to most on level streets.

But there's one situation in particular where this change is for the worse. Driving down an incline, decelerating as you approach a full stop intersection. If you cross a rough patch just before the stop, the car will suddenly surge forward as the regen cuts out. The only solution is to jump on the friction brake. I hit several of these scenarios each day here in San Francisco since we have plenty of significant hills, badly broken/patched pavement, and a stop sign or traffic light nearly every block. This programming change has made the i3's driving dynamics unpredictable and one-pedal driving more difficult for me.

I complained to the BMW i Genius line a few days after having the updates applied to my car. They claimed their software release notes didn't include a reference to brake regen changes so they'd consult with the engineers and get back to me. Never heard anything else of course.

FWIW the Leaf is notorious for this also, and actually there was one case with a driver that ended up hitting a guard rail because of it. Its kind of tricky I guess, the firmware has to catch it and immediately apply physical brakes?

 

[jadnashuanh]

I do not know the actual 'scale' on the regen, but someone said they changed the index value from the original of 27 to 24, or lowering the maximum regen on one of the s/w updates. It's noticeable, and I preferred it the way it was, but a new driver often found it hard to drive smoothly. SO, to accommodate them, they bumped it for all.

 

[epirali]

I do not know the actual 'scale' on the regen, but someone said they changed the index value from the original of 27 to 24, or lowering the maximum regen on one of the s/w updates. It's noticeable, and I preferred it the way it was, but a new driver often found it hard to drive smoothly. SO, to accommodate them, they bumped it for all.

I wonder why they just didn't add a couple of settings, like "aggressive, medium, mild" in the iDrive? Could have been part of the user profile.

Seems simple enough.

 

[MikeS]

I do not know the actual 'scale' on the regen, but someone said they changed the index value from the original of 27 to 24, or lowering the maximum regen on one of the s/w updates. It's noticeable, and I preferred it the way it was, but a new driver often found it hard to drive smoothly. SO, to accommodate them, they bumped it for all.

I wonder why they just didn't add a couple of settings, like "aggressive, medium, mild" in the iDrive? Could have been part of the user profile.

Seems simple enough.

+1

I to liked it as it was.

 

[Technicks]

Yes, I noticed the behavior change after the update that reduced the brake regen level in general. I believe multiple, severe bumps now causes the regen to cut out completely. Part of the effort to make it "easier" for the average, inattentive driver. Many poorly-trained drivers unconsciously lift off the accelerator when hitting rough pavement. They're used to the coasting action of a typical ICE car. With the i3's original behavior, brake regen would cause a significant slow down. Now the regen momentarily drops completely so the car coasts over rough pavement. The action probably isn't noticeable to most on level streets.

But there's one situation in particular where this change is for the worse. Driving down an incline, decelerating as you approach a full stop intersection. If you cross a rough patch just before the stop, the car will suddenly surge forward as the regen cuts out. The only solution is to jump on the friction brake. I hit several of these scenarios each day here in San Francisco since we have plenty of significant hills, badly broken/patched pavement, and a stop sign or traffic light nearly every block. This programming change has made the i3's driving dynamics unpredictable and one-pedal driving more difficult for me.

I complained to the BMW i Genius line a few days after having the updates applied to my car. They claimed their software release notes didn't include a reference to brake regen changes so they'd consult with the engineers and get back to me. Never heard anything else of course.

Ok, i was about to start a post on this but it looks like i'm not alone.
The problem i'm having here is not only with the braking, but also with accelerating. (I go over a few train tracks on my way to and from work, 5 sets to be more exact).
If i am stepping on it, and go over a bump where it lifts up a little, it cuts the acceleration completely (lets it "cruise" for a couple seconds) - this is also dangerous because the guy behind me expect me to keep accelerating (I live near Chicago, all drivers here have a screw loose), but instead acceleration drops to 0. This makes you get your foot off the acceleration for a second, and since there is no regenerative braking either, when the regenerative braking kicks back on, car slows down. At that point you slowed down twice before accelerating.
If anyone has a solution for this please let me know. I will be experimenting with traction control off for a few more days to see if i can get this behavior to change at all.
I'm also open to coding changes as I've coded plenty of features on the car already.

And to stumbledotcom's note about dangerous situations, i have something similar - train tracks right before a light. If light turns red, my foot automatically is lifted off the acceleration. If i do this before the train tracks, as i cross the tracks, regen cuts out and car approaches intersection at higher speed than desired. If there are cars in front of me, it's quite a scare, as that one extra second of braking can make the whole difference between crashing and not crashing into the car in front of you. Off course, i have learned this over the course of driving, so now i approach situations like this with more caution. Still, it's something that needs to be addressed.

 

[Jeffj]

I beleive the deactivation of acceleration (and regenerative braking) when the wheels lose grip - like when going over train tracks - is a direct result of real-world situations where the drive-shaft was getting sheared. The motor in the car is very powerful, and if the wheels lose grip, it can spin the wheels much faster very quickly (well under a second). When the wheels get grip again, they are spinning much faster than when they left the ground and this produces pretty severe strain on the driveshaft. It seems like they took the least painful alternative - controlling the motor/regen - rather than trying to re-engineeer a beefed up driveshaft.

Note, this is my deduction from reading/observing, its not an official BMW position.

 

[Blue20]

Sorry if this has been discussed before but I have now noticed a couple of times that if I am going over a small bump or a drop in the road when the car suspension lifts a little bit the car has a sudden short burst acceleration. It stops as soon as the weight settles back down.

Anyone else notice this?

Yes, same here. I've learnt to go over speed bump dead slow.

I think the issue is the i3 computer uses same program for ICE . The i3 electric motor reacts a lot quicker than ICE, so there is a jerk.

 

[WoodlandHills]

I beleive the deactivation of acceleration (and regenerative braking) when the wheels lose grip - like when going over train tracks - is a direct result of real-world situations where the drive-shaft was getting sheared. The motor in the car is very powerful, and if the wheels lose grip, it can spin the wheels much faster very quickly (well under a second). When the wheels get grip again, they are spinning much faster than when they left the ground and this produces pretty severe strain on the driveshaft. It seems like they took the least painful alternative - controlling the motor/regen - rather than trying to re-engineeer a beefed up driveshaft.

Note, this is my deduction from reading/observing, its not an official BMW position.

I didn't know that driveshafts were breaking too, I thought it was just motor mounts that were affected by wheel hop and hard accelleration.