9-speed gearboxes save how much fuel?

8-speed automatics have been around in German cars for a while. Now I hear that 9-speeds will be fitted to many SUVs in order to meet new fuel economy regulations. I saw one claim that they would save 10% fuel over a 5-speed box. The 9-speed has a lower first gear as well as closer ratios. I find this hard to believe unless the engine has a narrow RPM band for maximum efficieny.
Reply to
bruce56
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That probably is the case, or more correctly, we're targeting a narrower RPM band of the very highest efficiency.

I wonder how much of this efficiency is coming at the cost of reliability and durability however. I seriously doubt that these new multi-speed transmissions are built to the same safety margins as, say, an old TF727 3-speed... otherwise they'd weigh significantly more!

nate

Reply to
Nate Nagel

Perhaps. One engineer stated that gearboxes will not go above 11 ratios, as it is not feasible to squeeze more gears into a package that fits in a car.

Reply to
bruce56

That's when you go with double gearboxes, or an adjustable differential, to multiply the number of actual gears.

OR, you go to a stronger metal for the gears so that they can be made smaller, although at this point I don't think we have a good one.

--scott

Reply to
Scott Dorsey

have some faith in rags: cvt is not without shortcomings. coupled to a four banger that's all in vogue these days (thanks obama) that duo sounds in concert like your average dentist's drill

if you really perverse you could you the brave new world achievements from hybrid arena and pipe canned V-8 sound through the speakers though. don't like to have a stereo in your car? tough! have to have that shit these days for surrogate sound purposes

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