2 1 AUGUST 2019 AUTOCAR.CO.UK 15
NEWS
Toyota RAV4 to get
plug-in hybrid model
New GLB from £34k
TOYOTA HAS BEEN seen
testing a plug-in hybrid
variant of the RAV4.
The prototype SUV features
a disguised opening on its
right-hand side – the opposite
side to where the fuel filler
cap resides – which is a classic
te l l t a l e th a t a c h a r g i n g p o r t i s
lurking underneath.
Toyota wouldn’t officially
comment, but the TNGA
platform has been designed
to house a mix of powertrains,
with a fully electric e-TNGA
variant under development.
Car makers need to meet
strict fleet average emissions
targets for 2020/21, and
despite Toyota’s advocacy
of its ‘self-charging’ parallel
hybrid system, plug-in hybrids
with a more substantial
all-electric range are the most
effective short-term solution to
reduce CO 2 ratings.
I t ’s m o st l i ke l y th a t a p l u g - i n
hybrid RAV4 would continue to
use the 2.5-litre Atkinson-cycle
four-cylinder petrol engine
mated to a larger electric
motor and lithium ion battery.The current sole plug-in
hybrid power in Toyota’s
arsenal – the 1.8-litre unit in
the Prius Plug-in – is unlikely to
offer enough power and torque
to suit the larger, bulkier RAV4.
Expect an all-electric
range of about 30 miles in a
plug-in hybrid RAV4. It will rival
models such as the Mitsubishi
Outlander PHEV and Vauxhall
Grandland X PHEV.
THE UK PRICING and specs
of the new Mercedes-Benz
GLB have been released. The
compact SUV is available
to order now, priced from
£34,200 for the GLB 200
Sport, which uses a 161bhp
1.3-litre turbo petrol engine.AMG Line trim adds
another £1500 and brings
the option of four-wheel
drive. Further engine options
include a 2.0-litre diesel
offering 148bhp in the GLB
200d and a 187bhp version
in the 4x4-only GLB 220d.
Flagship AMG LinePremium Plus starts at
£41,700. First deliveries are
tipped for December.
RAV4 plug-in is likely to pair its electric motor with a petrol 2.
A FAIR NUMBER of different automated
transmissions have been tried over the years
but the most successful and enduring has
to be the torque-converter-based epicyclic
gearbox. New kids on the block like DCT
(dual-clutch transmission) and even grown-
up variants of CVT (continuously variable
transmission) have threatened to knock the
world’s favourite auto from its pedestal, but
none has succeeded yet.
That said, the classic automatic
transmissions didn’t earn the moniker‘slush ’boxes’ for nothing. The name
derives from the ‘slushy’ response of early
transmissions, which got people from
A to B but were hardly rewarding to drive.
Torque converters are fl uid couplings that
connect the engine to the transmission
instead of a clutch. They look like large
metal doughnuts but internally contain
three main components plus automatic
transmission fl uid. The engine side is the
impeller and on the transmission side is
the turbine. Both contain blades and look
similar to those you see in a jet engine when
you’re climbing the steps to an aircraft.
The impeller fl ings the transmission
fl uid outwards through centrifugal force
as engine revs build and into the turbine,
which is forced to rotate, driving the
transmission. The fl uid is forced back to the
centre of the impeller in a continuous cycle.
This isn’t the whole story, though, and
there’s a third component that turns what
would be an ineffi cient fl uid coupling into
the more effective torque converter. It’s
called a stator (because it stays still) and
sits between the impeller and turbine. Thestator defl ects the fl uid on its return trip to
the impeller slowing it down and, in doing
so, multiplies the torque between the engine
and transmission.
So far so good: when the car accelerates
from rest, the torque converter delivers that
satisfying slingshot feeling when you put
your foot down. Once at cruising speed,
though, the turbine (transmission side)
can never quite keep up with the speed of
the impeller (engine side), increasing fuel
consumption and emissions. Once those
things started to matter more, transmission
WHY THEY’RE SO AMAZING
designers added a lock-
up clutch to the torque
converter to mechanically lock
the two halves together at cruising speed.
Whereas the arrangement of the gears
in a DCT gearbox resembles that of a
manual, the inside of a traditional automatic
transmission is quite different. Instead
of gears arranged one above the other on
shafts, autos traditionally use epicyclic
(sun and planet) gearsets arranged one
after the other in a line. Using clutchesto control which way the torque is routed
through each gearset creates different gear
ratios. Adding more gearsets creates even
more gear ratios, so three gearsets could
deliver six forward speeds.
Torque-converter gearboxes are clever
and maybe a little fi endish, but although
drivability has improved a lot over the years
and they’ve always been refi ned, they need
to become more effi cient. More on how
transmissions boffi ns achieve that next week.
Torque converters may not look much
but they are one of the most amazing
devices ever to grace a driveline. They
take the place of a clutch, they multiply
torque between the engine and the
gears and they are still the choice when
refinement matters most.
THE AUTOMATIC CHOICE FOR
REFINEMENT: TORQUE CONVERTERS
Torque
converter-
based gearboxes
are the original
type of automatic
transmission and
they’re evolving
fast.
UNDER
THE SKIN
JESSE CROSSE
SPY SHOT
TOYOTA RAV4 PLUG-IN
GLB i s o n s a l e n ow,
with first deliveries
tipped for December