[bigblackwolf]

I have a 2011 X3 28i with the 8speed ZF automatic gearbox.
When driving out of town in the hills, I prefer driving "manual" and select the correct gear anticipating bends in the road and slope up or down. That way, I can select the gear better than the automatic, which only knows the actual driving condition, but cannot anticipate what is coming next.

Especially on longer slopes down, I prefer engine braking over wheel braking. But with the ZF, when shifting down , often I have the impression that the gearbox shifts down, but there is not a significant car deceleration.

Anyone has the same experience? How does the drivetrain on the X3 work in those conditions? How to get better manual engine braking with the 8speed ZF?

[Steve30dMSport]

I guess the main reason is due to the fact it has eight speeds and therefore they are very close compared to a typical 4 or 5 speed auto. This reduced differential means a smaller increase in revs and therefore reduced engine braking. if the ratios were more highly spaced you would have a significant increase in engine revs and therefore greater engine braking.

However, as a very good mechanic once told me 25 years ago: brakes are cheaper than transmissions.

[n55x3]

Yes, good point, if I was going to wear down an item it would be brake pads first.

Our X3 downshifts very nice when coming to a stop. In fact when you lift off the gas it slows down quicker than any of our current vehicles. I suspect this is due to the automatic down shifting of the 8spd (regular trannys actually go into somewhat of a free-wheel state where they do feel like they can cruise for ever when you lift) and the brake regeneration when off the gas probably attributes to some drag as well.

Now when we went up Mt Washington last spring there were some insane grades and we just kept it in 2nd or 3rd and it really had no problem holding a decent speed.

Keep in mind though, there is no denying gravity and if you are going down extremely steep grades then quite possibly no amount of engine braking will provide enough assistance.

[Ural]

When going down a hill-not an extremely steep one- typical highway down grade for instance- to prevent the car accelerate due to the slope, I hit the brake once for just one second and X3 locks at the current speed . If I want to gain speed , then I touch the gas just once and engine braking ( or whatever that mechanism is called) is off , car is loose again. Shift is in D all the time I do those.

[cadman50]

Originally Posted by n55x3

Now when we went up Mt Washington last spring there were some insane grades and we just kept it in 2nd or 3rd and it really had no problem holding a decent speed.

Could you have used the Hill Descent feature for the trip down?

[n55x3]

Originally Posted by cadman50

Could you have used the Hill Descent feature for the trip down?

Probably but like Lotus mentioned it would be less than ideal due to eliminating your biggest stopping power, the front rotors.

I do plan on playing with HDC during our off-road excursions. We are hoping to hit up Moab for some back country camping next fall and there are numerous trails where HDC will come in handy. But all are very short decents.

[Ant Man]

A good rule of thumb to apply when descending hills is to use the same gear that one would use to travel up it. That way, there is less chance of overheating the brakes and you also have more control over the car so that it does not 'run away' - this is advanced driving as taught by the IAM and RoSPA in the UK.

[bigblackwolf]

Originally Posted by Ural

When going down a hill-not an extremely steep one- typical highway down grade for instance- to prevent the car accelerate due to the slope, I hit the brake once for just one second and X3 locks at the current speed . If I want to gain speed , then I touch the gas just once and engine braking ( or whatever that mechanism is called) is off , car is loose again. Shift is in D all the time I do those.

Hello Ural,
I tried this, but the only thing I see is that the car slows down due to the foot brake action, but I do not really sense an engine braking. Actually, the gearbox does not shift down, because with no gas applied, the gearbox stays in D, probably at a high gear in order to reduce fuel consumption, but this does not give engine braking.

I now found the following comfortable and smooth (X3 28i):
When going down a slope, initially I take gas away. After a while, when further slowing down is required, then I shift the gear stick from D to M/S. In this "sport" mode, the gearbox shifts down 1, maybe 2 gears, and there is a comfortable braking feeling. Next, when further braking is required, if engine speed is low enough, I manually downshift 1gear. If engine speed is too high, I apply footbrake first.
I only do this if small and slows steps are required for the driving conditions. With large and fast changes, I use D and foot braking. Generally, I try to aim for relaxed and smooth driving at low engine speed without fast acceleration or deceleration. It is maybe a different driving style from other people that seek performance, but the X3 has this fine quality of smooth relaxed driving and the 6cylinder and 8speeds is excellent for that.
I am looking forward to some comments.

[lbjgh]

Want more engine braking? Turn on your rear window defroster.

... really. The alternator charges on deceleration so that'll improve engine braking. :P

[KF]

Hi X3 is still on the boat. Current 6speed ZF transmission car I only need to engage the cruise control to maintain the speed down hill, I expect the 8 speed to be a least as good. If your open road cruise control speed is too fast just reduce the cruise speed by 10 or 20kph!! These current tech transmissions have a higher IO than most of us drivers!!

KF NSW

[Ural]

Originally Posted by bigblackwolf

Hello Ural,
I tried this, but the only thing I see is that the car slows down due to the foot brake action, but I do not really sense an engine braking. Actually, the gearbox does not shift down, because with no gas applied, the gearbox stays in D, probably at a high gear in order to reduce fuel consumption, but this does not give engine braking.

I now found the following comfortable and smooth (X3 28i):
When going down a slope, initially I take gas away. After a while, when further slowing down is required, then I shift the gear stick from D to M/S. In this "sport" mode, the gearbox shifts down 1, maybe 2 gears, and there is a comfortable braking feeling. Next, when further braking is required, if engine speed is low enough, I manually downshift 1gear. If engine speed is too high, I apply footbrake first.
I only do this if small and slows steps are required for the driving conditions. With large and fast changes, I use D and foot braking. Generally, I try to aim for relaxed and smooth driving at low engine speed without fast acceleration or deceleration. It is maybe a different driving style from other people that seek performance, but the X3 has this fine quality of smooth relaxed driving and the 6cylinder and 8speeds is excellent for that.
I am looking forward to some comments.

Hi Wolf, I too don't see any downshifting of the automatic while I do that, but the car maintains its speed unless it's a steep hill . On regular long descends where your car tends to gain some speed , it should work for you too.

[xDrive35i]

Originally Posted by bigblackwolf

I have a 2011 X3 28i with the 8speed ZF automatic gearbox.
When driving out of town in the hills, I prefer driving "manual" and select the correct gear anticipating bends in the road and slope up or down. That way, I can select the gear better than the automatic, which only knows the actual driving condition, but cannot anticipate what is coming next.

Especially on longer slopes down, I prefer engine braking over wheel braking. But with the ZF, when shifting down , often I have the impression that the gearbox shifts down, but there is not a significant car deceleration.

Anyone has the same experience? How does the drivetrain on the X3 work in those conditions? How to get better manual engine braking with the 8speed ZF?

BMW's double-VANOS variable valve control actually creates significantly less engine braking than other engines. I'm not sure why they do it, but I think it may have something to do with linearity for efficiency? Lotus?

[bigblackwolf]

Originally Posted by juddholland

BMW's double-VANOS variable valve control actually creates significantly less engine braking than other engines. I'm not sure why they do it, but I think it may have something to do with linearity for efficiency? Lotus?

I think Valvetronic also plays a part. Valvetronic reduces valve lift at part load, and improves engine efficiency because it eliminates the losses that are normally associated with the throttle valve. So that is good for engine efficiency during normal driving. But it is those throttle losses that contribute to the engine braking and they are absent with Valvetronic/Double-Vanos.

[Rogerbu]

Is there a similar process in the diesel engine?
or does standard engine braking still operaate?

[x3heh]

Trade-offs.

http://articles.latimes.com/2010/oct...ility-20101027

If people had any idea about the absolute complexity of these products they would be stunned that they start every morning

[Rogerbu]

Re post 18 - Lotus7.

Thanks for the excellent informative response on Diesel engine braking. I use the limited engine braking when going downhill towing a caravan and wondered why it wasn't as effective as with a petrol/gas engine.

For the first time I also now understand the 'No Engine Braking' signs around some towns. I thought that it was aimed at me in my diesel car.

[cadman50]

Originally Posted by Lotus7

HDC does use maximum engine braking by switching to a lower gear and also actuating the rear brakes only. HDC can be set to a maximum speed of 15 mph/25 kph only.

If more braking is needed on long descents, than can be provided by engine braking only, you're generally better off using the full service brakes, rather than HDC, because HDC works on the rear brakes only and can overheat them if used on a long hill. On a X3, the rear brake pads are about half the size of the fronts, and have much less total energy absorption ability.

HDC is really designed for short, very steep, off-road type descents (that most X3s will never see).

Why would they only use the rear brakes on a steep downhill when it seems that's the time you need all 4 wheels in control?