B or D?
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- Posts: 14
- Joined: Sun Aug 27, 2023 3:25 pm
I'm the opposite. I drive in B mode most of the time. I only use the brake pedal to come to a complete stop. Right from the get-go I worked out what I needed to do to have smooth deceleration in an appropriate distance. It's all about situational awareness and not being in a particular hurry to get anywhere. I can't see the sense in using the brakes when it is not necessary. I give the brakes a small workout now and again, just to make sure I don't get rust build-up on the friction surfaces.
The first stage of pedal braking is regen resistance and then heavier braking via discs and drums so you may still not be using the actual mechanical side of the braking system much. I brake in N once a week or so to make sure the discs in particular get a clean up.rusty-away wrote: ↑Thu Dec 14, 2023 5:34 am I'm the opposite. I drive in B mode most of the time. I only use the brake pedal to come to a complete stop. Right from the get-go I worked out what I needed to do to have smooth deceleration in an appropriate distance. It's all about situational awareness and not being in a particular hurry to get anywhere. I can't see the sense in using the brakes when it is not necessary. I give the brakes a small workout now and again, just to make sure I don't get rust build-up on the friction surfaces.
I flit between B and D dependent on where I am in my journey. That said, despite my hardest efforts to read traffic I always get highest miles/kW when in B.
Born V2-Tech L collected June 22
BMW Z4 e89 sDrive30i Highline
BMW Z4 e85 3.0i SE
BMW Z4 e89 sDrive30i Highline
BMW Z4 e85 3.0i SE
I've been happily driving my first 3k miles in B, hardly ever using the brake pedal and getting 5.6 miles/kW locally. But M-way efficiency has been a relatively disappointing 3.5 miles/kW averaging 73mph
(I hardly use Aircon at all; I use Cruise Control very proactively, and aggressively in busy M-way traffic)
BUT. On my M-way drive today I inadvertently had it in D for the last of three segments .... and the efficiency suddenly shot up.
Now this is nowhere near enough data to rely on but I will now be experimenting
(In the meantime does anyone know of any physics reason why this MIGHT be the case?)
(I hardly use Aircon at all; I use Cruise Control very proactively, and aggressively in busy M-way traffic)
BUT. On my M-way drive today I inadvertently had it in D for the last of three segments .... and the efficiency suddenly shot up.
Now this is nowhere near enough data to rely on but I will now be experimenting
(In the meantime does anyone know of any physics reason why this MIGHT be the case?)
I've barely used B, my logic being that if when you come off the throttle you start braking (regen) it must be wasting energy. Regen won't claw back 100% of the energy used to build up that speed so surely (physics?!) says that it's better to coast and then use the brake (even if it's is regen) as little as possible
V3 58kwh e-boost in Quasar gray.
- mluisbrown
- Posts: 238
- Joined: Wed Mar 08, 2023 4:46 pm
- Location: Lisbon, Portugal
If you're using Cruise Control as you say, then it's completely irrelevant whether you're in B or D. When the car needs to slow down, it will do so in the most efficient manner, using only regen braking if possible, and adding physical braking if not.
As I've mentioned earlier in the thread, the only thing that B or D mode changes is the way you control the speed of the car. Either by mostly using the accelerator pedal (B mode) or using the brake and accelerator pedal just as you would in an ICE car.Baconrage wrote: ↑Mon Jul 29, 2024 6:57 pm I've barely used B, my logic being that if when you come off the throttle you start braking (regen) it must be wasting energy. Regen won't claw back 100% of the energy used to build up that speed so surely (physics?!) says that it's better to coast and then use the brake (even if it's is regen) as little as possible
So in your example, if you come off the throttle in B mode, it will start braking using regen. If you were in D mode and wanted to slow down the same amount, you would have to use the brake pedal, which would also use regen unless it needs to brake harder than regen can provide, in which case the physical brakes are used.
"so surely (physics?!) says that it's better to coast and then use the brake (even if it's is regen) as little as possible"
You can coast in B mode as well. You maintain the position of the throttle pedal that gives you the speed you'd like to go. If it's possible to maintain that speed by coasting, then the car will coast and not use any extra energy. If you're going downhill it may even regen to keep you at the speed you want. You can see in the energy bar on the dash when the car is regenerating (green bar) or using power (blue bar). If the car has a very high state of charge (close to 100%) you may notice that the regen bar maxes out earlier than normal. That's because it's not possible to regen that much with such a high SoC.
I've said it before, and I'll say it again: B or D mode MAKE NO DIFFERENCE to efficiency. They are simply modes that determine how the driver controls the speed of the car, nothing more. B mode allows more one-pedal driving, D mode is like a normal car.
2023 Born 58kWh, Glacial White, 19" Typhoon Copper, Skyline, Blue Dinamica electric seats, Cargo, Privacy, Pilot M+, Tech M
2003 Audi A3 8L 1.9TDi PD 130 with 360,000kms.
2003 Audi A3 8L 1.9TDi PD 130 with 360,000kms.
Mluisbrown
"I've said it before, and I'll say it again: B or D mode MAKE NO DIFFERENCE to efficiency. They are simply modes that determine how the driver controls the speed of the car, nothing more. B mode allows more one-pedal driving, D mode is like a normal car"
I think a lot of newer EV drivers don't immediately understand the regen on the brake pedal before mechanical friction braking. I do however find always a difference in efficiency between driving in D v B. I've been on the MEB platform for almost 4 years and find that if I'm doing short urban runs B will often return in excess of 5 miles/kw whereas in D I will get maybe upper 4s. So I think there is a difference for each driver and their style of driving and the journey they are on. I flit between B and D on a trip with a preference of D on open roads and B in traffic. I have a long term average of 4.2 miles/kW over 25 months never reset so I'm doing something right.
Bottom line though is enjoy the drive the way you prefer. The efficiency difference in my experience between D and B is small in my driving style and journeys but the car always puts a smile on my face. It's a great drive
"I've said it before, and I'll say it again: B or D mode MAKE NO DIFFERENCE to efficiency. They are simply modes that determine how the driver controls the speed of the car, nothing more. B mode allows more one-pedal driving, D mode is like a normal car"
I think a lot of newer EV drivers don't immediately understand the regen on the brake pedal before mechanical friction braking. I do however find always a difference in efficiency between driving in D v B. I've been on the MEB platform for almost 4 years and find that if I'm doing short urban runs B will often return in excess of 5 miles/kw whereas in D I will get maybe upper 4s. So I think there is a difference for each driver and their style of driving and the journey they are on. I flit between B and D on a trip with a preference of D on open roads and B in traffic. I have a long term average of 4.2 miles/kW over 25 months never reset so I'm doing something right.
Bottom line though is enjoy the drive the way you prefer. The efficiency difference in my experience between D and B is small in my driving style and journeys but the car always puts a smile on my face. It's a great drive
Born V2-Tech L collected June 22
BMW Z4 e89 sDrive30i Highline
BMW Z4 e85 3.0i SE
BMW Z4 e89 sDrive30i Highline
BMW Z4 e85 3.0i SE
- mluisbrown
- Posts: 238
- Joined: Wed Mar 08, 2023 4:46 pm
- Location: Lisbon, Portugal
Fair enough Daveion 
If there is a difference in efficiency between D and B modes it's not something inherent to the mode, but a difference in how each driver uses these modes.
I personally use mostly B, and only use D for motorway style driving if I'm not using cruise control).
If there is a difference in efficiency between D and B modes it's not something inherent to the mode, but a difference in how each driver uses these modes.
I personally use mostly B, and only use D for motorway style driving if I'm not using cruise control).
2023 Born 58kWh, Glacial White, 19" Typhoon Copper, Skyline, Blue Dinamica electric seats, Cargo, Privacy, Pilot M+, Tech M
2003 Audi A3 8L 1.9TDi PD 130 with 360,000kms.
2003 Audi A3 8L 1.9TDi PD 130 with 360,000kms.