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2019+ BMW 3 AND 4-SERIES FORUMS (G2x Generation) General G20 Sedan / G22 Coupe / G26 Gran Coupe Discussions Coasting in Eco Pro or Comfort mode to save fuel

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      08-14-2019, 01:55 AM   #1
Eagle Creek
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Hey guys,

According to the manual, in Eco Pro or Comfort mode, the car uses a "coasting" to reduce fuel consumption. Indeed, I noticed during my test drive that the HUD shows an icon to signal the driver to lift off from the gas when going down hill. But, I don't understand why the G20 prefers to disconnect the engine from the gearbox (which requires fuel to keep the engine running) in order to achieve savings.

Here's why. When I drive my E90 down hill, and I lift my foot off the gas, the consumption meter goes to zero while the car maintains quite some speed, only slowing slightly due to the engine. By comparison, when I put the car in neutral (just for testing), the consumption meter actually rises. On the other hand, there's no engine braking effect anymore, and therefore I'm able to maintain speed longer or even see an increase in speed when going downhill.

Conclusion: when the engine is not connected to the wheels, some fuel is needed to keep it running. However, when it is connected to the wheels, no fuel is needed to keep it running.

What am I not seeing here ?
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      08-14-2019, 02:17 AM   #2
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While coasting, speed reduction is as minimal as possible. Especially on slight declines you will notice constant speed. That compensates for the little gas needed.
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      08-14-2019, 02:29 AM   #3
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So what you are saying is BMW chooses to use a little bit of gas to keep the engine running and by doing so prolonging the amount of time no additional gas for acceleration is needed?

Imo this would only be beneficial at modest declines for a reasonable amount of distance. At more steep declines keeping it in gear the weight of the car alone should keep it rolling with 0 usage of gas. Does the car indeed detect this and in this case choose the keep the engine connected to the wheels?

I drove a manual KIA in France last summer, went down a hill in second gear and didn't have to give any gas for almost 5 full minutes. Just going down in 2nd and breaking ever so slightly every now and then. Absolutely no gas needed.
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      08-15-2019, 04:39 AM   #4
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Appearantly coasting isn't available at a more steep decline:

https://www.bimmerpost.com/forums/sh...php?p=25140361
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      08-15-2019, 08:06 AM   #5
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I don't think the E90 had coasting (was introduced with F30 after a few production years). Therefore, what are you comparing your G20 coasting mode to in your E90? Is your E90 a manual that you would put into neutral/clutch-engaged, or an automatic you would actually shift into neutral? Or would you keep it in gear and just take your foot off the gas?
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      08-15-2019, 09:13 AM   #6
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Quote:
Originally Posted by Pauleebe View Post
what are you comparing your G20 coasting mode to in your E90? Is your E90 a manual that you would put into neutral/clutch-engaged, or an automatic you would actually shift into neutral?
From the second paragraph of his post:

"By comparison, when I put the car in neutral (just for testing), the consumption meter actually rises."

He does not specify what type of transmission the car has, but that is actually immaterial to the experiment. The point is to disconnect the engine from the wheels, which is what putting the transmission in neutral does.

Quote:
Or would you keep it in gear and just take your foot off the gas?
From the second paragraph of his post:

"When I drive my E90 down hill, and I lift my foot off the gas, the consumption meter goes to zero while the car maintains quite some speed, only slowing slightly due to the engine."
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      08-15-2019, 09:26 AM   #7
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Quote:
Originally Posted by Eagle Creek View Post
So what you are saying is BMW chooses to use a little bit of gas to keep the engine running and by doing so prolonging the amount of time no additional gas for acceleration is needed?
It would seem that that is the logic, yes. Perhaps the car can glide for short periods as well?

https://en.wikipedia.org/wiki/Gliding_(vehicle)

That would provide the best of both worlds - no fuel used and no energy loss to the frictional forces inside the engine. However, this might not be safe to do without 48V (which the G20 does not have yet), because the electro-hydraulic braking system may require more energy than could be provided by the battery alone, and it might not be possible to fire up the engine quick enough to provide that in a panic situation.
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      08-15-2019, 02:26 PM   #8
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Regardless, I averaged 40MPG in EcoPro mode. Was actually almost 42MPG for most of a 400 mi trip until the last 150 mi when I was going through the Catskill Mtns on Rt 17.
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      08-15-2019, 03:09 PM   #9
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Quote:
Originally Posted by mkoesel View Post
That would provide the best of both worlds - no fuel used and no energy loss to the frictional forces inside the engine. However, this might not be safe to do without 48V (which the G20 does not have yet), because the electro-hydraulic braking system may require more energy than could be provided by the battery alone, and it might not be possible to fire up the engine quick enough to provide that in a panic situation.
I'd say the 330e should be able to do so having the electric engine available as an immediate backup.

What do you mean by 48V? Volts?
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      08-15-2019, 03:57 PM   #10
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Quote:
Originally Posted by Eagle Creek View Post
So what you are saying is BMW chooses to use a little bit of gas to keep the engine running and by doing so prolonging the amount of time no additional gas for acceleration is needed?

Imo this would only be beneficial at modest declines for a reasonable amount of distance. At more steep declines keeping it in gear the weight of the car alone should keep it rolling with 0 usage of gas. Does the car indeed detect this and in this case choose the keep the engine connected to the wheels?

I drove a manual KIA in France last summer, went down a hill in second gear and didn't have to give any gas for almost 5 full minutes. Just going down in 2nd and breaking ever so slightly every now and then. Absolutely no gas needed.
Yes, it detects this. Downhill is only free coasting for a while, after that the clutch is engaged and you're braking on the motor.
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      05-21-2020, 08:35 PM   #11
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Hi, may I ask how do you know that coasting is activated when driving in Comfort mode?
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      05-21-2020, 09:23 PM   #12
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Quote:
Originally Posted by sddz6269 View Post
Hi, may I ask how do you know that coasting is activated when driving in Comfort mode?
It doesn't coast in comfort, only in eco-pro. When doing so, the rpm's will be around 1000. It's basically putting the car in neutral.
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      05-22-2020, 04:13 AM   #13
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Quote:
Originally Posted by sddz6269 View Post
Hi, may I ask how do you know that coasting is activated when driving in Comfort mode?
You will see this blue car icon. You can activate coasting yourself by pulling the upshift paddle twice fairly quickly.

Quote:
Originally Posted by Spec23 View Post
It doesn't coast in comfort, only in eco-pro
It does but less often. Depending on your driving style.
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Last edited by hamera; 05-22-2020 at 10:15 AM..
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      05-22-2020, 06:47 AM   #14
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Quote:
Originally Posted by hamera View Post
You will see this blue car icon. You can activate coasting yourself by pulling the upshit paddle twice fairly quickly.



It does but less often. Depending on your driving style.
Thank you very much! I can't wait to test it. Since I coded coasting using bimmercode, I'm not sure if it can be activated under Comfort mode.
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      05-22-2020, 08:02 AM   #15
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Quote:
Originally Posted by hamera View Post
You will see this blue car icon. You can activate coasting yourself by pulling the upshit paddle twice fairly quickly.



It does but less often. Depending on your driving style.
Don't think mine has ever done that but thanks!
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      05-22-2020, 08:46 AM   #16
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Quote:
Originally Posted by hamera View Post
You will see this blue car icon. You can activate coasting yourself by pulling the upshit paddle twice fairly quickly.



It does but less often. Depending on your driving style.
Tried mine after reading this. The ‘pulling the upshit paddle twice fairly quickly.’ worked for me in Comfort mode. Didn’t get it to work every time but it did go into coasting.
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      05-22-2020, 09:24 AM   #17
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Quote:
Originally Posted by Eagle Creek View Post
I'd say the 330e should be able to do so having the electric engine available as an immediate backup.

What do you mean by 48V? Volts?
330e can do this, f30 330e was already doing this. When coasting the engine is turned off, no matter what charge battery system has.
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      05-22-2020, 10:29 AM   #18
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Quote:
Originally Posted by Spec23 View Post
Don't think mine has ever done that but thanks!
Yeah, I imagine not many BMW drivers care about this feature at all. Saving fuel? Are you mad?
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      05-23-2020, 02:27 AM   #19
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The only time i use ECO Pro is if I'm cruising with little traffic, Other than that I like to have quick access to power.
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      05-23-2020, 04:02 AM   #20
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Quote:
Originally Posted by SoFlo_Nick View Post
The only time i use ECO Pro is if I'm cruising with little traffic, Other than that I like to have quick access to power.
Agreed. Eco pro makes the throttle slow to respond. I found myself in a situation unable to overtake as quickly as I wanted and thereby hindering other traffic. That's why I don't use Eco Pro that often anymore.
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      05-23-2020, 11:47 AM   #21
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Quote:
Originally Posted by hamera View Post
Yeah it's nothing to do with 48V instalation.

The engine isn't turned off. It's idling when coasting. Still injects fuel to keep it running. It still better to coast than engine brake under certain scenarios
For 330e the engine is for sure turned off, not idling. In eco pro the 330e is coasting/"gliding"
with no engine braking (so not charging batteries either).

Nothing to do with 48V yes, but he/she was wondering if 330e would be able do this.
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      05-23-2020, 12:10 PM   #22
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Quote:
Originally Posted by kaipajo View Post
For 330e the engine is for sure turned off, not idling. In eco pro the 330e is coasting/"gliding"
with no engine braking (so not charging batteries either).

Nothing to do with 48V yes, but he/she was wondering if 330e would be able do this.
My mistake. I was thinking about normal petrol engine, not the hybrid.
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