Rubbish. Modern automatic transmissions like Porsche's PDK, SMG,
DSG, SST,etc offer unparalled up and downshifting timing with
minimal power loss. In fact, as compared to their manual
counterparts, they offer better fuel consumption, faster 0-100
timings and higher top speeds, to name some advantages. I agree
with purplejade that a major factor might be to keep costs
down.
20% power loss? I wonder which century you are living in?
There's a stark difference between fully auto gearbox with
manual overide and sequential manual gearbox. for BMW's SMG, its a
sequential manual box with fully auto option. essentially, its a
manual gearbox not unlike those found on motorbikes and F1 cars.
just that it offers fully auto mode as an option with the computer
taking over for gear shifting. the downside is that when in fully
auto mode, there will be delay when it comes to shifting gears and
shift shocks are very pronounced. most other auto gearboxes with
+/- works just like a normal auto gearbox, just that it offers the
driver with the option of shifting gears. they still have the
traditional torque converter.
Volkswagen's DSG and Nissan's GR6 gearboxes are basically
twin-clutches auto gearbox. it offers faster shift times mainly due
to the dual clutches which engage the next gear even before the
gear is selected.
its true that modern auto gearboxes offers better fuel economy,
but that's only restricted to bigger engines. smaller engines with
auto gearboxes generally consumes more fuel than manual ones. small
cars like Honda Fit however manages to obtain excellent fuel
economy is due to the fact that it uses a CVT gearbox.
power loss on an auto box can range from 5% to 15%, mainly due
to the power sapping torque converter. and when it comes to
maintenance, a manual box is far more easier to maintain than an
auto box.
