Audi and BMW to utilize 8-speed gearboxes to take on Lexus

[coolraoul]

How could this be ridiculous? The technical innovation increases both performance and fuel efficiency.

There is nothing wrong with this type of war if:
1. Performance is improved
2. Fuel consumed is reduced, and
3. The customer ultimately benefits.

I don't care if the number of gears eventually increases from 8 to 20. As long as the progress is justified by the criteria above.

I was merely joking... Over the fact I have 3 gears and now the carmakers are making 8 gears...

However, I fear this could be a bit like a "I have more than you" piss-contest. I'm not sure increasing from 6 to 7 then 8 gears really give a decisive benefit (mainly in fuel consumption). Marketing could have its word here.

But i'm no engineer. Just found funny to see that many gears, while my car puts the third (and last) at 50km/h and only downshifts if I need to quickly overtake someone...

 

[Cashmere]

is the auto stop-start feature the one that automatically engages the brake when the car is taking off on an incline?

or is it the one where the car automatically switches off when the car is idle?

 

[Mr Robert]

is the auto stop-start feature the one that automatically engages the brake when the car is taking off on an incline?

or is it the one where the car automatically switches off when the car is idle?

It is the latter.

 

[Wolfgang]

is the auto stop-start feature the one that automatically engages the brake when the car is taking off on an incline?

or is it the one where the car automatically switches off when the car is idle?

The first one is Hill Start Assist:



Continental Automotive Systems USA - Hill Start Assist (HSA)

 

[EnI]

As it was all said in the development brief: they had striven for best solutions in efficiency, torque-to-weight ratio, performance, refinement, modular design etc and 8-speed auto proved to be the best possible solution ... the best compromise in a given time (and given R&D money).

They didn't have a goal to develop a certain number of gears for marketing reasons - to top or fight rival products. Otherwise they would go for 9 or 10 gears, don't you think?

 

[coolraoul]

As it was all said in the development brief: they had striven for best solutions in efficiency, torque-to-weight ratio, performance, refinement, modular design etc and 8-speed auto proved to be the best possible solution ... the best compromise in a given time (and given R&D money).

They didn't have a goal to develop a certain number of gears for marketing reasons - to top or fight rival products. Otherwise they would go for 9 or 10 gears, don't you think?

Not necessarily. Dealing with 10 gears is incredibly harder than dealing with 7, that's why the carmakers don't do 10 yet. But it'll come, when the chips will allow that and the materials will reduce the weight. A jerky 10 gears box isn't a good idea, better sticking to 8 but making it fast and smooth!

I'd like to know the real benefit of having 8 over 6 or 7.

The E200/220/250 cdi is said by some to get the 7G soon, we'll see if the consumption really drops that much from the 5G.

It'll give a hint, even if the design is older and the motor itself will maybe get some minor mods too.

 

[Wolfgang]

Not necessarily. Dealing with 10 gears is incredibly harder than dealing with 7, that's why the carmakers don't do 10 yet.

The ML has 10 already... Wait a minute, I'll look for a blurb from the sales brochure when it first came out in 1998. One moment please...

Here it is...

Mercedes-Benz StarShift®

"Twelve speeds and the brains to use them. Five forward speeds and one reverse are more choices than some SUVs offer, but the M-Class gives you twice that. Push a button and the electronic transfer case shifts into low range: The ML320's 38.59:1 crawl ratio is the lowest of any automatic SUV. The notched shift gate lets you downshift and withhold upshifts like a manual gearbox. Or let the driver adaptive control select the shift points that best match the road and how you're driving it, from desert byway to open highway to snowy switchback."
text Mercedes-Benz

 

[coolraoul]

No, no, that's not 10 gears. It's a reduction.
Hit a button, and the gear ratio (of the whole gearbox) is reduced. A Land Rover Defender has that, too.

The reduced ratio is not used in the road, 'cause it limits the speed (max speed must be somewhere around maybe 80 km/h in fifth with the reduced ratio). And you can't put the higher ratio at speed (must be possible at low speed though).
The reduction is used for off-road (reduced ratio means the gears are way way shorter, giving more power at low speed, useful to climb severe hills or to get massive motorbrake, and allows more sensitivity in the power delivery.

So the chip doesn't deal with 10 gears, only five. Only there is one "program" for the road, one for all-terrain.

Some people with very slow 4x4 (Lada Niva, old Toyotas, slow-powered G-Wagen) do use the reduced ratio in city to have more power, as they don't need a big max speed in town.

Funny thing, is the smart Fortwo of the first generation: to save weight and space, it has a three-gears gearbox with a reduction. And when in third gear, instead of engaging the fourth gear (which doesn't exist), it switches the ratio and engages the first gear, this time without reduction, so that the first becomes the fourth gear... Samewise, when downshifting to third, in fact it engages the reduction and puts the third gear...

This is the only example of a car that uses the reduction for the road, and doing so as a normal behaviour.


So the ML has a 5 gears box. Not 10. So do every true 4x4 boasting a reduction for all-terrain use.

 

[Wolfgang]

Hello coolraoul,

I found another Mercedes sales prospectus mentioning an 8 speed transmission. Does this one count?

From the MBUSA 2010 ML450 HYBRID sales brochure:

"The ML 450 HYBRID’s CVT — Continuously

Variable Transmission — optimizes power
and efficiency seamlessly at all speeds,​

and offers an 8-speed manual shift mode."

Source: http://www.mbusa.com/mercedes/data/pdf/brochures/2010-M-Class.pdf

 

[vabboud]

that also doesn't count.
this is a CVT, which in essence is like 2 pulleys with a belt between, and the pulleys vary in size to determine ratios.

in CVT mode, the box varies between a lower bound ratio (first gear) and a higher bound ratio (top gear), while visiting the infinite possibilities between both.

new CVTs have manual modes. the lever sports +/- like a tiptronic box. this 8 speed merc box, is a regular CVT with 8 preset ratios which the CVT pulley and belt contraption moves to when you "shift"

 

[Wolfgang]

BMW stuck a picture of this transmission onto their server:

From:

BMW EfficientDynamics : BMW Concept X6 ActiveHybrid : The energy management

 

[coolraoul]

Hello coolraoul,

I found another Mercedes sales prospectus mentioning an 8 speed transmission. Does this one count?

From the MBUSA 2010 ML450 HYBRID sales brochure:

"The ML 450 HYBRID’s CVT — Continuously

Variable Transmission — optimizes power
and efficiency seamlessly at all speeds,​

and offers an 8-speed manual shift mode."

Source: http://www.mbusa.com/mercedes/data/pdf/brochures/2010-M-Class.pdf

Hi Wolfgang!

Nice try, but... Well, no, it doesn't count actually...
I'm sorry...

What is complex is to make the chip choose the right gear at the right moment. Not too soon, not too late. And to do so with comfort, reactivity, economy, motorbraking in mind.
And of course, the more gears you have, the more complex it is!!!

Here, for the hybrid ML... Because it's a CVT, it doesn't really feature 8 gears. A CVT has no fixed gears, it continuously adapts the revs to the situation. Therefore, the electronics don't deal with 8 gears.

The 8 gears the brochure speaks about are artificial gears that are created specificly for the manual mode.

These 8 gears are only there in manual mode, when the gearbox is in automatic mode it doesn't materially change gears at all in fact.

So the chip doesn't need to choose between 8 gears. It just changes the ratio according to the needs... It's only when you put it in manual mode that the system "creates" 8 different, artificial ratios you can choose from.

Think about it like that: in automatic, it's like a wheel to control the volume of the radio. You turn it just as you want, there are no fixed intervals.
In manual, it's a + and a - button: you have fixed intervals.

 

[Wolfgang]

Update.

BMW wants to cancel their six-speed automatic contract which was supposed to run through 2015. It seems GM Strasbourg has been supplying BMW transmissions since 1991?

Handelsblatt: BMW wants to end alleged collaboration with GM


PS. Maybe it weighs too much?

weight wet: 85-90 kg from http://archives.media.gm.com/archive/documents/domain_39/docId_25969_pr.html

To compare:

MB 7Gtronic is only 76kg, fluid included.

 

[Deleted member 25]

1 billion, it's huge sum.

 

[Zafiro]

Update.

BMW wants to cancel their six-speed automatic contract which was supposed to run through 2015. It seems GM Strasbourg has been supplying BMW transmissions since 1991?

They have new 8-speed automatic so of course they dont want a 6-speed anymore.

 

[Wolfgang]

^^

Also, the Getrag 7DCI600 weighs 79 kg (dry).

GETRAG Corporate Group - 7DCI600 TRANSMISSION

 

[Zafiro]

^^

Also, the Getrag 7DCI600 weighs 79 kg (dry).

GETRAG Corporate Group - 7DCI600 TRANSMISSION

and? is it a problem?

 

[Wolfgang]

^^

Looks like BMW might now prefer an 8-speed auto or 7-speed dual clutch transmission over the planned 6-speed.

MB's in house developed 7G-Tronic seems to have a slight weight advantage.

 

[Zafiro]

^^

Looks like BMW might now prefer an 8-speed auto or 7-speed dual clutch transmission over the planned 6-speed.

MB's in house developed 7G-Tronic seems to have a slight weight advantage.

I dont think those differences are going to make a impact on the performance of the car.
BMW's new 8-speed automatic is better and more efficient than their 6-speed automatic thats why they are replacing their older gearboxes.

 

[Wolfgang]

^^^
Great.

PS. Mercedes is working on a new in-house developed transmission, with "at least 8 speeds".
It's expected around 2014, according to jesmb.de.

PSS. Didn't see this Car and Driver article yet posted on GCF? Might have overlooked it somewhere...

ZF’s 8-Speed Automatic Transmission - Tech Dept.
Now if six turned out to be eight . . .
BY K.C. COLWELL
December 2009

The eight-speed transmission is not new to the automotive world. Toyota has had one in its Lexus LS and IS F sedans for a few years. But now, transmission giant ZF is bringing eight speeds to the masses with promises of improved fuel economy.

It’s known by the folks in its hometown of Friedrichshafen, Germany, as the “8HP kit,” and this transmission offers myriad options for automakers. It is already in the BMW 760Li and 5-series GT. The new Rolls-Royce Ghost, Bentley Mulsanne, and Audi A8 will all be equipped with the 8HP when they roll out of factories in the coming year.

More: http://www.caranddriver.com/features/09q4/zf_s_8-speed_automatic_transmission-tech_dept