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2010 2011 BMW 5 Series Forum F10 BMW 5-Series (F10) Forums General 5-Series Sedan and Wagon (F10 / F11) Forum Is engine braking in the auto bad practice
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      12-14-2011, 11:37 PM   #1
MMVI
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Is engine braking in the auto bad practice

I have a 520d msport with the paddle auto. It's my first auto box and as a manual die hard I must say that I have very quickly become used to and even enjoy not having to declutch to change gear.

It's not perfect though it can ever be as only I the driver can see out of the window and what is coming. Consequently I use the excellent paddles all the time, preparing the car for a tight bend etc or just placing it in the right gear at the exact right time. It can be a lot of work as there are 8 to step through but it can be useful and fun.

But here is the question. Whilst in a manual I almost never did the step down through the gears when coming to a stop (obviously not in the auto either) but I did tweak gaps between me and others or hold position when going down hill especially by dropping a gear.

I find myself paddling down two or sometimes three gears to do the same.
The auto sometimes gives a rev match but also can brake the engine.

Does this do the transmission any long term harm.

I could of course brake but as any of you superb drivers out there will know/were taught/believe as a principle... That in itself is bad practice/lazy/giving in...
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      12-15-2011, 02:26 AM   #2
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nothing wrong with the engine braking in either manual/auto. Unless you're engine braking to 4k rpm every stop....
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      12-15-2011, 03:24 AM   #3
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The only time I use the paddles is for engine braking on long descents. I've tried them in normal conditions, but there's simply too many gears to choose from. That's not a criticism; I love the sport auto box and I think it does an excellent job without my clumsy intervention.
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      12-15-2011, 03:55 AM   #4
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Can't do any harm, as the older 6-speed boxes have features which enable engine braking, can't see the 8-speed being any different. (Haven't got any 8-speed data at hand).

On downward slopes the 6-speed will initiate a down change itself, to hold a speed, due to how you use the throttle/brake. Fast lift off of the throttle, to zero position will hold a gear rather than change up, (all conditions) so initiating engine braking. Plus a light dab on the brakes will, on inclines, initiate down changes and engine braking.

I often drive in the mountains or hilly conditions, and use the techniques to benefit from engine braking whenever I want, even in auto mode. In snow, I use the manual step' function to get the precise control of engine braking I'm after.


Would be worth experimenting, to see if any of these techniques help you to engine brake, without having to always 'paddle' through the gears.

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      12-15-2011, 10:39 AM   #5
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Will it harm the engine, no. It it necessary, no. Unless you are going down the Stelvio pass and worried about cooking your brakes, all your doing is burning fuel to save brake life. Brakes are cheaper, easier to fix and you can replace them in perpetuity.
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      12-16-2011, 03:04 PM   #6
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I do it all the time and found this topic interesting. I had never considered fuel consumption.

Everything I have read suggests BMWs use Deceleration Fuel Cut-Off (DFCO). No fuel is burned under the right conditions. It is suggested that it can increase overall fuel efficiency by 2%. Maybe the Efficient Dynamics indicator is triggered by this?

http://en.wikipedia.org/wiki/Engine_braking
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      12-17-2011, 09:04 AM   #7
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Quote:
Originally Posted by gatoman39 View Post
...all your doing is burning fuel to save brake life...
I can't quote actual figures, but with your foot off the throttle, the fuel burn won't be significantly more than it is at idle.
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      12-17-2011, 09:58 AM   #8
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Quote:
Originally Posted by Jon D View Post
I can't quote actual figures, but with your foot off the throttle, the fuel burn won't be significantly more than it is at idle.
You're probably right, it's not much, but you are repeatedly putting load on the drivetrain to brake the car, as opposed to just using the brakes. I can understand doing this in a panic situation or exiting a motorway at a high rate of speed, other than that, seems unnecessarily. Especially when brakes are free during the warranty period.
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      12-17-2011, 10:10 AM   #9
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Quote:
Originally Posted by gatoman39 View Post
Will it harm the engine, no. It it necessary, no. Unless you are going down the Stelvio pass and worried about cooking your brakes, all your doing is burning fuel to save brake life. Brakes are cheaper, easier to fix and you can replace them in perpetuity.
I'm pretty sure the car cuts the fuel supply going downhill with the fot off the throttle.
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      12-17-2011, 10:18 AM   #10
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FWIW, the car "blips" the throttle as the autobox downshifts. I do notice the instant F/E guage jump and settle back down.
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      12-17-2011, 12:31 PM   #11
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That is interesting. Here we have 2 years of warranty, but that does not include any wear parts like brake pads. A track day driven wrong could easily wear out a couple of pads and I don't see BMW changing them for free.
Engine braking is a good thing.
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      12-17-2011, 05:46 PM   #12
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Quote:
Originally Posted by remmib View Post
I'm pretty sure the car cuts the fuel supply going downhill with the fot off the throttle.
I agree. Notice the ED indicator turns off when the RPMs drop below 1000. It needs to burn fuel to maintain a safe idle RPM.
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