Use of ZF 8-speed auto gearbox (BMW and other makes)

Topics relating to Advanced Driving in cars
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Horse
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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby Horse » Sat Jun 16, 2018 7:49 pm

Cloggie: why didn't you buy a manual box car?

Regards: straight-gears; interesting comment in one of Chris Gilbert's DVDs, where he says "Changing gear with the steering set" ie not changing the steering at the same time as changing gear.

Edit: bloomin spell checker ...
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fungus
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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby fungus » Sun Jun 17, 2018 1:59 pm

That's how I taught learners. Use enough gas to build speed up sufficiently to be able to take second whilst the steering is set when moving off from a standstill at a roundabout. If they were too gentle with the gas they would go round in first, most uncomfortable. I had an associate a few years ago who hadn't mastered it in seven years of driving.

Nigel.

Diesel
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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby Diesel » Tue Jun 19, 2018 9:41 pm

One thing I will say, the ZF box on the 335D is incredible.

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Mr Cholmondeley-Warner
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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby Mr Cholmondeley-Warner » Sat Jun 23, 2018 7:17 am

I'm with earmark (waremark - autocorrect! :D ) and Gareth. D for town work, full manual for the open road. And if you need to drop your hands a bit, that's probably not a bad thing ;)
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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby Jonquirk » Sat Jun 23, 2018 12:57 pm

Even in town you might feel the need to intervene. I was driving a Mercedes Sprinter box van with a seven speed auto box. On some downhill sections I felt it necessary to push the lever into manual to hold a gear and maintain my chosen speed with engine braking before switching back to auto mode when the ground levelled out.

TheInsanity1234
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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby TheInsanity1234 » Mon Jun 25, 2018 4:55 pm

In the days of old where brake fade was a very real and common problem, I could understand the hesistance to use brakes - but modern braking systems are so good that I wouldn't have thought using the brakes to control your speed going downhill would be such an issue now?

I always thought the whole point of an auto was to simplify the driving experience to a simple "Right is go, Left is stop" kind of style, so you don't have to worry about pressing the clutch and fiddling with BGOL stuff, and trying to pick an appropriate gear for the situation, you just prod the throttle or the brake to adjust your speed, and the gearbox does the rest of the work?

I have never driven an automatic so my ramblings are entirely theoretical!

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Strangely Brown
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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby Strangely Brown » Mon Jun 25, 2018 5:15 pm

TheInsanity1234 wrote:In the days of old where brake fade was a very real and common problem, I could understand the hesistance to use brakes - but modern braking systems are so good that I wouldn't have thought using the brakes to control your speed going downhill would be such an issue now?


It depends... for heavy vehicles and long descents fade can still be a problem. If dropping the auto into a lower gear hold helps to keep the speed in check then you have nothing to lose and everything to gain ?

TheInsanity1234 wrote:I always thought the whole point of an auto was to simplify the driving experience to a simple "Right is go, Left is stop" kind of style, so you don't have to worry about pressing the clutch and fiddling with BGOL stuff, and trying to pick an appropriate gear for the situation, you just prod the throttle or the brake to adjust your speed, and the gearbox does the rest of the work?

I have never driven an automatic so my ramblings are entirely theoretical!


Image

TheInsanity1234
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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby TheInsanity1234 » Mon Jun 25, 2018 5:59 pm

Strangely Brown wrote:
TheInsanity1234 wrote:In the days of old where brake fade was a very real and common problem, I could understand the hesistance to use brakes - but modern braking systems are so good that I wouldn't have thought using the brakes to control your speed going downhill would be such an issue now?


It depends... for heavy vehicles and long descents fade can still be a problem. If dropping the auto into a lower gear hold helps to keep the speed in check then you have nothing to lose and everything to gain ?

Fair 'nuff. Just seemed like it was needlessly complicating the operation of something which is designed to be simple to operate.

Strangely Brown wrote:
TheInsanity1234 wrote:I always thought the whole point of an auto was to simplify the driving experience to a simple "Right is go, Left is stop" kind of style, so you don't have to worry about pressing the clutch and fiddling with BGOL stuff, and trying to pick an appropriate gear for the situation, you just prod the throttle or the brake to adjust your speed, and the gearbox does the rest of the work?

I have never driven an automatic so my ramblings are entirely theoretical!

Image

The point was - why would you want to add extra layers of complication to a thing designed to simplify the operation of a vehicle. You want to slow down? Use the brakes. You want to speed up? Use the accelerator. Can't see how fiddling with pre-selecting gears and that would lend itself to any meaningful benefits. I could see it on track, or when driving at the limits, but in the majority of every day driving, I would have thought the standard 'D' program would be perfectly satisfactory?

One thing I would say was bizarre about some of the more modern auto boxes is that they have a 'coasting' feature designed in to the software, so that when the car detects that you're driving with very little throttle (for instance, on a very slight downhill incline, then they will disengage the clutch and allow the car to coast, which supposedly makes the car use less fuel (I don't quite understand this, but I know Audi boxes will do this in Eco mode). Seems smart, however the odditity of it is that, when you're going downhill on a steeper hill where you'd speed up without engine braking BUT you still need to have some throttle input to maintain your speed going down, the box will go into 'coast' mode. As you can imagine, this results in the car speeding up, so you put your foot on the brake to control your speed, but as soon as you do this, the gearbox will engage the engine to provide engine braking to assist you in slowing down, so you have to then take your foot off the brake and prod the accelerator to stop the car slowing down too much, and bam - coast mode is engaged again! Pointless rambling, I know, but does show that perhaps technology is starting to get so "intelligient" that it's making life awkward for the users who have to interact with said technology!

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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby Gareth » Mon Jun 25, 2018 7:11 pm

TheInsanity1234 wrote:The point was - why would you want to add extra layers of complication to a thing designed to simplify the operation of a vehicle.

I think they're not designed to simplify operation. Instead, I reckon they're designed to sell even more cars to disinterested punters, by enabling them to delude themselves into thinking it would simplify driving which, given their almost total lack of interest in driving, is very attractive.

TheInsanity1234 wrote:One thing I would say was bizarre about some of the more modern auto boxes is that they have a 'coasting' feature designed in to the software, so that when the car detects that you're driving with very little throttle (for instance, on a very slight downhill incline, then they will disengage the clutch and allow the car to coast, which supposedly makes the car use less fuel

Are you sure about this? Generally, light throttle will allow the gearbox to change up to the highest possible gear, possibly to reduce frictional losses by making the engine turn slower. In turn this means there is precious little engine braking, which would feel very similar to disengaging the clutch in a car with a manual gearbox. If the clutch is disengaged, fuel is used to keep it turning, whereas a minimal amount of fuel is used if the engine is just providing enough power to maintain the current speed with hardly any load, none at all if on the overrun.
Last edited by Gareth on Tue Jun 26, 2018 4:54 am, edited 1 time in total.
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GTR1400MAN
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Re: Use of ZF 8-speed auto gearbox (BMW and other makes)

Postby GTR1400MAN » Mon Jun 25, 2018 9:32 pm

Yep coasting has existed on a lot of autos for several years.

Now we have stop/start while coasting. Arrrggghh!

https://www.motor1.com/news/147835/2018 ... -function/
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