8-speed dual clutch gearbox in the works

[Dieter]

Hi,

Quote from link below:

"The new Mercedes dual-clutch gearbox is expected to feature eight speeds as well as engine stop-start and hybrid compatibility."

http://www.motorauthority.com/mercedes-likely-to-build-dual-clutch-transmissions-in-house.html

I like the stop/start bit but is 8-gears one too many?

Cheers,

 

[st4]

2 too many if you ask me

 

[wemorgan]

As I understand it engines are at their most efficient when at a certain RPM. So by having more gears, more of the driving time is spent near to this optimal RPM.

 

[jeremytaylor]

I agree with ***.

I sometimes think that the 7G-tronic has one gear too many, and the standard tip box has 1 too few. 6 would be enough for me!

 

[st4]

As I understand it engines are at their most efficient when at a certain RPM. So by having more gears, more of the driving time is spent near to this optimal RPM.

Well go for a CVT transmission....

 

[Dieselman]

CVT can't handle high torque outputs so a multi geared auto is used.

 

[st4]

I'd in that case rather have a 6speeder....

 

[st13phil]

Actually, 8-speeds doesn't really surprise me. Consider the narrow peak torque band of the latest generation of small capacity / high output diesels and it makes eminent sense.

 

[wemorgan]

I'd in that case rather have a 6speeder....

I wasn't trying to tell you which gearbox design to buy, as clearly that's your business, but simple to explain why MB are coming up with 8sp gearbox designs.

 

[popuptoaster]

going backwards if you ask me, way back in the 50's the yanks were building hi torque V8's that ran 2 speed auto's, all me mates seem convinced more gears is better, but to me it just means the engines are more peaky and not so nice to drive.

 

[st4]

Actually, 8-speeds doesn't really surprise me. Consider the narrow peak torque band of the latest generation of small capacity / high output diesels and it makes eminent sense.

I also wonder if its to keep up with the competition. Lexus have an 8 speed unit, whereas MB don't so people will think the lexus GBox is better.

In sometimes occasions, and I suspect this is one of them, less is more. But tell that to the marketing bods.

 

[raymont]

I would have thought more gears gives the opportunity to better match the road speed to the engine speed to deliver optimum acceleration and / or economy.

My car has a seven speed transmission (ignoring reverse and transfer box in case someone gets pedantic) and for the majority of the time I don't know or care which gear is currently selected and changes are pretty much imperceptible. So, going by my experience, if 8 or even more gears were used I wouldn't really notice, except perhaps in the areas of more responsive performace and enhanced fuel economy.

 

[jeremytaylor]

CVTs should stay where they started - in DAFs, and certainly nowhere near a Merc (just my humble opinion!)

 

[Dieselman]

CVTs should stay where they started - in DAFs, and certainly nowhere near a Merc (just my humble opinion!)

Why.?

 

[popuptoaster]

oops

 

[popuptoaster]

CVTs should stay where they started - in DAFs, and certainly nowhere near a Merc (just my humble opinion!)

i'll agree with that, horrible road manners most of em.

Autos need big torquey engines, if its weedy and peaky enough to need 8 speeds its just not a good engine for an auto box.

 

[wemorgan]

Autos need big torquey engines, if its weedy and peaky enough to need 8 speeds its just not a good engine for an auto box.

But I suppose the point is that MB are developing the 8sp g-box to increase efficiency and not because their engines are too weedy and peaky.

 

[popuptoaster]

But I suppose the point is that MB are developing the 8sp g-box to increase efficiency and not because their engines are too weedy and peaky.

most modern engines are weedy and peaky, to many valves and turbos is the problem, i dont think it has much to do with efficency, any marginal mpg or performance increase will easily be outweighed buy the extra weight,cost and complexity, its got more to do with marketing.

"mmmm more is better! i must buy the new 8 speed merc to impress the neighbours!"

 

[DITTRICH]

I've always felt 5 speed auto was enough and only regretted the lack of a sixth "overdrive" gear when zipping down the motorway. Eight speed? What next? What use is shaving a few percent off the co2 figures when the gearbox wears out more quickly (thus necessitating a new one) How much co2 is a new gearbox worth anyway?
Les

 

[st4]

most modern engines are weedy and peaky, to many valves and turbos is the problem, i dont think it has much to do with efficency, any marginal mpg or performance increase will easily be outweighed buy the extra weight,cost and complexity, its got more to do with marketing.

"mmmm more is better! i must buy the new 8 speed merc to impress the neighbours!"

Thats exactly it. Porsche did the same back in the 1990's. The 964 had a 5 speed manual box and the engines torque was sufficient but the 993 came out with 6 speeds, purely to compete in numbers with Ferrari. A local driving expert, IAM, track day enthusiast sort told me the 5 spd car was better.