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Reader Comments for
Subscribe to this threadAudi and BMW to utilize 8-speed gearboxes to take on Lexus
(Page 1 of 1)
Josiah @ May 12th 2008 3:02PM
Dumb question (I'm honestly ignorant on this topic; is there a point where adding "gears" becomes less effective (both performance and efficiency wise) then employing a CVT? Is that where we are headed?
Michael Harley @ May 12th 2008 3:14PM
Current CVTs may be torque limited...
Mark @ May 12th 2008 3:50PM
I'm not sure, but please use commas instead of parens.
Carlos @ May 12th 2008 3:39PM
Yes it does, and if companies would invest the amount of money it takes to develop a new gearbox into a CVT, it wouldn't take that long to develop one that isn't torque limited. There are applications using hydraulics that can be used but their weight is an issue and they aren't as efficient as using the belt system in current CVTs because of fluid losses in compressing the hydraulic fluids.
yacoub @ May 12th 2008 4:09PM
Yes, and there are several diminishing returns:
more gears in the same space = smaller gears = less durable. more gears = more shifting = increased wear on clutch packs and shift mechanisms. more gears = car is always shifting = unsettling driving experience for those used to a more normal amount of shifts. more gears = more shifting = higher transmission temps from more frequent activity = shorter lifespan or need for additional cooling capacity.
and the list goes on...
Johnny @ May 12th 2008 4:20PM
Thank god vacoub is not an engineer at an automaker anywhere. Or we be driving 1 speed automatics with his logic.
pmiddle5 @ May 12th 2008 4:31PM
^^^^why is that a bad thing? I still want a regular manual option though. Slower, heavier, ancient, I still want it
Disgruntled Goat @ May 12th 2008 5:01PM
If you look at the top fuel misers you'll see they all use CVTs or 4 to 5 speed boxes. I suspect the 8 speed auto is driven by the marketing guys, not the engineers.
Derek @ May 12th 2008 9:21PM
CVT's generally have higher drive line losses than conventional transmissions.
Pmiddle - manual transmissions are typically lighter than an automatic of equal gears. Manuals can be faster than their auto counterparts as well but it requires an experienced driver rather than just placing a brick on the gas.
Mal Fuller @ May 12th 2008 6:47PM
There's that old standby called the law of deminishing returns. Whatever happened to the KISS theory?
Joel @ May 12th 2008 7:03PM
@Johnny - He could also be implying diminishing or non-existent returns after so many gears.
yacoub @ May 13th 2008 11:10AM
@Johnny: Was clearly talking about the recent rise of 7+ gear transmissions. @__@