On Mon, 2005-08-29 at 22:55 +1200, Russell McMahon wrote:
> > Then what do you do when starting and stopping?  If you want an 
> > automatic box, just get one - there's lots of
> > reasons why automatics aren't just a manual box with actuators!  :-)
> 
> But the "best" ones are. ie when "real" people (red cars with 12 or 
> more cylinders and images of prancing horses come to mind *) make auto 
> changing or tip-tronic style systems they add actuators (usually 
> hydraulic) to a manual box. The principle advantage of an automatic 
> system is arguably the torque converter which allows the engine to 
> "reach below" the road speed range in a given gear which it otherwise 
> would be able to. This is also in many ways its prime disadvantage - 
> engine and wheels aren't totally talking to each other. The power loss 
> in a modern auto transmission is not a major factor unless you want 
> every ounce of power from a given engine. (An interesting unit of 
> power, the ounce ;-) ).

Actually with most modern automatics there is practically no more power
loss, at speed.

Many automatic transmissions have something called "torque converter
lockup", which essentially is a hydraulically activated clutch (usually
controlled with an electrical solenoid by the computer). The only
difference is this clutch is only designed to engage at "cruising"
speeds, it is not designed to bring you off the line. With this clutch
engaged the torque converter is completely bypassed, mating the engine
directly to the transmission. You get the benefit of easy starts at
lower speeds, and no power loss in the torque converter at cruising
speeds.

As further proof of this, most of the new cars in North America that
have standard transmissions as an option (which is pretty rare outside
of sports cars) have fuel mileage ratings that are the same for either
automatic transmissions or standard. There are even a few cases where
the automatic transmission equipped car has BETTER fuel economy (which
used to be unheard of).

Of course, with all this said, my next car will likely be equipped with
a standard transmission, just like the feeling of control it gives you.
Plus, it's doubtful a car thief would be interested in it, few can drive
stick! :)

TTYL


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