ZF CEO thinks 9 speeds is enough

[ne_one]

ZF CEO thinks 9 speeds is enough
Automotive News
November 6, 2012
by Douglas A. Bolduc

The nine-speed transmission might be where the race to add gears ends, ZF Friedrichshafen CEO Stefan Sommer said.

He referred to nine speeds as the "natural limit" because going beyond that number adds weight and complexity that cannot be offset by gains in fuel efficiency.

"There is no hard line, but you have to consider the law of diminishing returns. The question is whether adding even more gears makes sense," he told the Automobilwoche Congress here today. Automobilwoche is Automotive News Europe's German sister publication.

Not long after ZF introduced its eight- and nine-speed transmissions, a press report said that Hyundai Motor Group was developing a 10-speed gearbox. Last month, a separate report said that General Motors and Ford are jointly designing nine- and 10-speed automatic transmissions for broad use across their vehicle lineups in a bid to boost fuel economy.

Earlier this year, Julio Caspari, president of ZF's North American operations, hinted that a "Can-you-top-this?" race to add gears may be driven by marketing considerations rather than fuel economy.

That's because there is only an 11 percent gap between the most-efficient transmissions today and a theoretically perfect gearbox, he told Automotive News Europe sister publication Automotive News.

Full article at link.

[roy219]

If "there is no hard line" according the ZF CEO, why not 10 forward ratios, like my Trek bicycle?

[megeebee]

ZF is, I believe, an extention of the original Zeppelin Company, and the Zeppelin Metalworks, that built airships in the early 20th Century.

[BlackGTP]

I think one gear for each mph. So if your car can go 100mph, there should be 100 gears. It will take a hour to accelerate to 60 to hit each gear.

[AMERICA 123]

In these types of apps...... ie where the 8 /9HP apply, perhaps the next frontier isn't about more gear count...... but rather..... everything else including some 'new' things and configurations.



Unless.......... you want to start downsizing so you can start 'loading' PV engines like Class Eights..........

[CJH]

I would expect a more informed statement from the CEO, because it really depends on what you are trying to do, unless he was referring to a specific class of vehicle. A heavier vehicle like trucks/SUV's will benefit from more gears. EX: Semi trucks. There is always a cost/weight benefit you have to weigh, but who knows what will be developed, as there is still room for improvement in current transmissions.

[hunchman]

All vehicles need 13 speed trannies with dual dipsticks and performance floor mats. Don't stop at 9

[germeezy1]

In these types of apps...... ie where the 8 /9HP apply, perhaps the next frontier isn't about more gear count...... but rather..... everything else including some 'new' things and configurations.



Unless.......... you want to start downsizing so you can start 'loading' PV engines like Class Eights..........

The briliiance of the ZF 8HP, and 9HP is often hidden within a discussion about total number of gears when there is so much more beneath the surface of these innovative transmissions.

[germeezy1]

I would expect a more informed statement from the CEO, because it really depends on what you are trying to do, unless he was referring to a specific class of vehicle. A heavier vehicle like trucks/SUV's will benefit from more gears. EX: Semi trucks. There is always a cost/weight benefit you have to weigh, but who knows what will be developed, as there is still room for improvement in current transmissions.

He was specifically speaking about automotive transmissions, and the cost/ benefit ratio of rapidly increasing gear counts.

[spd98]

I want 3 reverse gears!

[AMERICA 123]

He was specifically speaking about automotive transmissions, and the cost/ benefit ratio of rapidly increasing gear counts.

Also...... and I do mean directly .......... you'll end up or likely will end up trading this for that in terms of mpg so with virtually no net gain - or even worse + all the other you mention.

Over simplified in a general sense but not in a specific sense for some - you'll actually end up trading city mpg for highway etc etc -


And then...... if you follow.......... highway for highway and city for city.

[CJH]

He was specifically speaking about automotive transmissions, and the cost/ benefit ratio of rapidly increasing gear counts.

I was referring to light car vs pickup/suv transmissions. I obviously didn't state my point very well. What I meant was that he might be correct for smaller cars, but trucks/SUV's could benefit from more, however how many more I do not know. And as stated, I understand the cost/weight/complexity question.

[kevinahcc20]

Highway HD diesel trucks need more gears because the ratio between redline and idle speed is much lower than in a LD automotive engine, so the gear ratio steps also need to be proportionally smaller. This topic was about how many gear ratio steps does a LD automotive engine need to reach maximum efficiency. The ZF CEO is suggesting that past 9 forward speeds the additional incremental efficiency gains from adding another forward gear will be offset by mass and frictional loss gains that result from the added gear. His fundamental point is clearly rational although in a "specsmanship" race like this the endpoint may well overshoot the optimum, like cup holders in a minivan!

[b4z]

I agree 9 is enough.
think about programming the transmission to kick down X amount of gears, seems like it would get confused.

Added weight complexity, clutch packs---when does it end?

And if the engine is low in tq. it is going to be hunting all over on hills.

[CJH]

Highway HD diesel trucks need more gears because the ratio between redline and idle speed is much lower than in a LD automotive engine, so the gear ratio steps also need to be proportionally smaller. This topic was about how many gear ratio steps does a LD automotive engine need to reach maximum efficiency. The ZF CEO is suggesting that past 9 forward speeds the additional incremental efficiency gains from adding another forward gear will be offset by mass and frictional loss gains that result from the added gear. His fundamental point is clearly rational although in a "specsmanship" race like this the endpoint may well overshoot the optimum, like cup holders in a minivan!

Except that you are discounting weight and aerodynamic drag. That's why often trucks pulling oversize/overweight trucks will be fitted with more gears vs a normal truck. Its not just about rev range.