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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > 2012-2019 BMW 3 and 4-Series Forums > General F30 Sedan / F32 Coupe / F36 Gran Coupe Forum > Engine Braking
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      05-03-2012, 11:49 PM   #23
Ganeshbabu2008
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In the case of auto box, Iím assuming that the braking process is split it two parts. The first part where the auto box down shifts to use engine braking alone and then the 2nd part when the actual braking begins to activate. Is the transformation from the 1st part to the 2nd seamless or is there some kind of indication available there? Thx.
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      05-04-2012, 10:11 AM   #24
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Quote:
Originally Posted by Ganeshbabu2008 View Post
In the case of auto box, Iím assuming that the braking process is split it two parts. The first part where the auto box down shifts to use engine braking alone and then the 2nd part when the actual braking begins to activate. Is the transformation from the 1st part to the 2nd seamless or is there some kind of indication available there? Thx.
Certainly the auto will down change on decceleration, but not to give effective engine braking, but to put the car in a gear where the engine speed is above idle, the revs typically only rise a few hundred rpm and it is a gentle stop.

Using the brakes briefly will intitiate engine braking. On a descent a quick dab on the brakes will instigate a down change, or two, if the brakes are dabbed hard enough. The box then typically holds the gear until you add a bit of throttle, to show you are wanting an up change.

Also going downhill the 'box will change down, if the car speed increases, thus enhancing the engine braking effect.

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      05-04-2012, 10:47 AM   #25
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If engine braking isn't really a factor on the N20, what's happening when I press the decelerate switch on the steering wheel when cruise control is engaged?

It definitely seems to slow the car down WAY more than just letting up on the gas pedal does without cruise engaged.

Does the cruise actually engage the brakes if you press down on the decelerate switch hard enough?

And if so, do the brake lights come on?
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      05-04-2012, 11:04 AM   #26
Feanor
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Originally Posted by glitched79 View Post
If engine braking isn't really a factor on the N20, what's happening when I press the decelerate switch on the steering wheel when cruise control is engaged?

It definitely seems to slow the car down WAY more than just letting up on the gas pedal does without cruise engaged.

Does the cruise actually engage the brakes if you press down on the decelerate switch hard enough?

And if so, do the brake lights come on?
I've been wondering how this works on the new cruise with brake function. I want to be able to let the car slow down by itself by reducing the cruise speed setting as I do at the moment. I don't want to waste fuel by the car applying the brakes unecessarily. If braking is needed I'll take control myself.
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      05-04-2012, 11:11 AM   #27
HighlandPete
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Originally Posted by Feanor View Post
I've been wondering how this works on the new cruise with brake function. I want to be able to let the car slow down by itself by reducing the cruise speed setting as I do at the moment. I don't want to waste fuel by the car applying the brakes unecessarily. If braking is needed I'll take control myself.
Brakes are applied if you overrun the set speed. Strange sensation, when it happens on my 330d. I also agree on not wanting to waste fuel.

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      05-04-2012, 09:42 PM   #28
Ganeshbabu2008
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Quote:
Originally Posted by HighlandPete View Post
Certainly the auto will down change on decceleration, but not to give effective engine braking, but to put the car in a gear where the engine speed is above idle, the revs typically only rise a few hundred rpm and it is a gentle stop.

Using the brakes briefly will intitiate engine braking. On a descent a quick dab on the brakes will instigate a down change, or two, if the brakes are dabbed hard enough. The box then typically holds the gear until you add a bit of throttle, to show you are wanting an up change.

Also going downhill the 'box will change down, if the car speed increases, thus enhancing the engine braking effect.

HighlandPete
Thx for that, pete. I was wondering how the auto box would control the linearity during engine braking and you've explained it well. I guess after elimination of the engine drag, double gear downshifts are not necessary during engine braking to work up the crank pulley.
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      11-05-2012, 08:33 PM   #29
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this is all part of the efficient dynamics. Somehow in sport mode i notice the engine brake is much more noticeable once foot leaves throttle. As for the rest of the driver modes the engine braking is reduced to allow for maximum coasting thus better fuel efficiency.
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      11-07-2012, 03:47 PM   #30
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Quote:
Originally Posted by HighlandPete View Post
Brakes are applied if you overrun the set speed. Strange sensation, when it happens on my 330d. I also agree on not wanting to waste fuel.

HighlandPete
I read somewhere that only the rear brakes are used when cruise control is decelerating. Not sure how truthful that is, but it is definitely a strange sensation.
Eee, back in our 330d days! Good times
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