[ technology, automotive ]
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[*2] source : "On to the tranny. The SportShift design on the Acura is like that of BMW's - that is, the manual shift gate is correctly located on the left side of the box, near the driver, and moves up for upshifts and down for downshifts. Very intuitive, very easy to use. However, like most automanual transmissions, the gearshifts weren't as crisp or quick as a true manual; there was little difference between leaving it in the automatic mode and rowing your own gears in the middle range. At highway speeds, however, the auto managed to get confused, becoming hesitant when going from 60 mph to 80; we really had to work for a downshift. Car manufacturers have yet to develop an automanual that works like a true manual tranny, and for a performance-oriented vehicle, we'd expect the option of a manual. "
 Consumer Guide Automotive, Trends, April 2005: <-begin quoted text-> "...many automatics can "hunt" among gears in certain driving conditions or select a higher gear before it's needed, creating a power "sag."... Today's manually shiftable automatics were designed so the driver can compensate for such annoyances. An idea pioneered by German sports-car power Porsche nearly two decades ago, these typically have a second shift gate marked "+" on one end and "-" on the other. Move the lever into this slot and you can select gears up and down in sequence. Some cars use steering-wheel buttons or "paddles" to supplement or replace the lever.
The manual mode in these automatics isn't as a versatile as a pure do-it-yourself transmission, which allows "short-shifting" from, say, 2nd to 4th gear. But it's good enough for most situations. And there's always straight Drive for when you're feeling lazy. Note, however, that the sportier "manumatics," like those from BMW, Infiniti and other brands, won't upshift or downshift without driver intervention. Other units, such as Mercedes', will shift automatically in manual mode, but won't go above the highest gear selected-for example, "4" or "5" in a 6-speed transmission.
A newer idea is the "automanual," exemplified by BMW's Sequential Manual Gearbox (SMG) and Audi's Direct Shift Gearbox (DSG). These are basically conventional manual transmissions fitted with an electronically operated clutch pack instead of a driver-operated clutch pedal. The driver shifts up and down the gears using a lever and/or steering-wheel controls, but the computer times clutch engagement so precisely that there's no gear grinding. These transmissions also include an automatic mode that changes gears for you according to road speed, throttle position, and so on.
CTVs have two distinct advantages over conventional automatics, they have fewer moving parts and are more compact. In the line drawing above you can see the simplicity of a CVT. Click on images to enlarge. Still another trend in transmission tech is the continuously variable automatic transmission or CVT. Instead of a set of gears with fixed drive ratios, a CVT uses the belt-and-pulley principle to furnish a near-infinite number of drive ratios. A computer determines the "right" one needed at a given moment. The idea is to keep the engine always operating at peak efficiency so as to maximize both performance and fuel economy. " <-end quoted text->