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DEVELOPMENT BACKGROUND
In 1995, sports car enthusiasts
around the world were delighted by the launch of the MGF. This marked the
return of the MG marque to volume-produced open sports cars for the first time
since 1980. It soon firmly established itself as the top selling sports car in
the UK, and began to sell strongly in export markets including Europe, Japan and
Australia.
Little production car development
was sanctioned in the BMW-era, apart from the introduction of the Stepspeed (CVT
/ six-speed) derivative in 1999, as part of the 2000MY update. However, when MG
Rover Group gained its independence in 2000, the pent-up enthusiasm of MG
engineers could at last be directed into a high-intensity programme for a
new-generation MGF.
The first inkling of the new
direction came with the exclusive MGF Trophy 160 SE model, announced in
January 2001. This drew from racetrack experience (MGF Trophy and MGF
Cup championships) and represented the ultimate high performance evolution of
the existing chassis and body. However the designers and engineers were now
thinking well beyond this, with ideas for significant advances in chassis, body
structure, aerodynamics, powertrain and style.
The launch of the MG TF,
nearly six months earlier than anticipated, once again demonstrates MG Rover
Group’s ability to deliver outstanding products within industry-leading time
scales and with an ethos to be ‘lean, mean and efficient’ with a ‘will to do’
central to everyone’s thinking.
The TF retains the ‘real
world’ affordability and practicality that set the MGF apart from rival
cars, but is even more faithful to the MG brand ethos of ‘Outrageous Fun For
All’.
CHASSIS: ENTIRELY NEW SUSPENSION
The simple substitution of
high-rate, compact coil springs for the Hydragas units, with unchanged
suspension linkages, had been evaluated experimentally some time ago, but this
would not have delivered the class-leading standards of handling and driver
involvement central to the latest generation of MGs. The challenge of
incorporating the latest technology in suspension geometry, coil springs and
gas-filled dampers within the MGF architecture was taken up.
Advanced computer design studies
were carried out to optimise the suspension geometry and elasto-kinematic
characteristics. Simulator vehicles confirmed the potential of the new system.
One thorough Main Board test-driving session with a simulator was all it needed
for motorsport enthusiast and MG Rover’s Product Development Director, Rob
Oldaker, to receive the green light for the new suspension concept to be fully
engineered to production status.
The rear suspension trailing arm
pivots from a forward extension of the subframe, forking at the rear to attach,
via firm bushes, above and below the hub carrier. This provides longitudinal
wheel location and reacts torque purely in the vertical plane. A maximum-length
link runs from the rear base of the hub carrier to a pivot on the centre rear of
the subframe, thus completing what is effectively a very wide-based lower
wishbone with a large swing radius.
The other links comprise the
upper suspension arm and a lower steer-control link mounted forward of the hub
carrier. A new rear anti roll bar, with modifications to suit the new
configuration, is operated by a short swinging link connected to the hub end of
each trailing arm. This new suspension combines optimum camber control with much
greater resistance to unwanted steer effects. It is the key to the MG TF’s
more responsive and throttle-adjustable handling, plus its improved steering
‘centre-feel’. Customers wanting an even more sporting edge to their TF
120, TF 135 or TF 160 can specify the Sports Pack 1, which has
suspension lowered by a further 10mm (i.e. 20mm lower than MGF).
Both front and rear subframes
were modified, with raised and angled turrets for the top mountings of the coil
over damper units. By moving the lower operating pivots for the spring units
further outboard on the upper suspension arms, more conventional leverage ratios
and spring rates could be employed compared with the previous system. The change
also meant that the damper forces were contained within the stiff subframes
instead of being fed into the bodyshell.
The subframes themselves are now
solidly-mounted to the bodyshell, as on the performance Trophy model,
contributing to enhanced structural
stiffness and precision of
control. Another advantage of the new suspension is that it allows a 10mm lower
ride height to operate, to the benefit of appearance, stability and handling. A
lower centre of gravity also reduces pitch under acceleration and braking.
At the front, the wishbone
suspension configuration otherwise remains similar to MGF, but with
reduced camber and parallel tracking in place of toe-out, plus revised pivot
bushes and a stiffer anti-roll bar, up from 19mm to 20mm diameter, to complement
the improved steering system. Tyre life is improved with this revised geometry.
It is in the rear suspension
(especially important on a mid-engined car), that the most fundamental changes
have been made. A completely new multi-link axle has been engineered to provide
precise control of rear wheel geometry in all conditions to offer exceptionally
involving and responsive control.
SHARPER STEERING
The MGF was one of the
first cars to exploit the packaging and energy-efficiency benefits of Electric
Power-Assisted Steering (EPAS). In the major chassis upgrade for the TF,
the steering has been given 10% ‘faster’ gearing; (the rack ratio goes from
19.0:1 to 17.5:1 with 2.8 turns lock to lock, from 3.1) for greater and sharper
steering response. In addition, the EPAS control software has been further
developed.
The speed-proportional system now
offers more weight at low speeds and a more progressive weight as speed
increases. To further enhance steering response, the lateral stiffness of the
rear pivot bush on each front lower wishbone has been increased. These changes
combine with the new suspension and increased body stiffness to give the new
TF even more enjoyable and confidence-inspiring steering qualities under all
conditions.
BEEFIER BRAKING
For the new TF 160 model,
MG/AP Racing front brakes similar to those introduced for the MGF Trophy
160SE model are specified. The front ventilated discs are 304 mm in diameter (up
from 240 mm) and the special stiffened alloy four-piston callipers are
red-finished to show behind the alloy wheel spokes. The TF 160 combines
this competition standard brake with ABS control. This TF 160 braking
specification is also available on TF 120 and 135 models as part of the
optional Sports Packs 2 or 3.
On ABS-equipped models (standard
on TF 120 and 160, optional on TF 115 and TF 135) the new
multi-link rear suspension layout has facilitated a revised brake effort
balance, allowing the rear brakes to work harder and reducing stopping
distances.
WHEELS AND TYRES
To fully realise the potential of
the new chassis, an extensive tyre development programme confirmed the benefits
of the 16" Goodyear F1 tyre and led to the specification of the new Continental
Premium Contact on 15" wheels. All TF models have alloy wheels as
standard, and all have wider tyres at the back than at the front to reflect the
mid-engine mass distribution.
Standard equipment on the TF
115, TF 120 and TF 135 are 15" x 6J wheels (eight-spoke on TF
115, square-spoke on the TF 120 and TF 135) with 185/55 R15 tyres
at the front and 205/50 R15 at the rear; the TF 160 has a new 11-spoke
design, 16" x 7J wheel with 195/45 R16 front and 215/40 R16 rear tyres.
A comprehensive range of 16"
wheel options is offered, either individually or as part of the Sports Option
Packs, including a ‘gunmetal’-finish ultra-lightweight 11-spoke design. A steel
spacesaver temporary spare wheel is standard on the TF 115, TF 120
and TF 135 models, with the option of the Instant Mobility System (IMS)
that comes as standard on the TF 160. IMS comprises a sealant gel and an
electric pump. The alternative option for TF 160 buyers is a spare
16"x7J, 11-spoke alloy wheel with 195/45 R16 tyre for temporary use.
AERODYNAMIC BALANCE
The striking new style of the
TF was carefully honed in the wind tunnel as well as in the studio to ensure
it delivered excellent lift balance – so important to a car’s dynamic behaviour.
The new front bumper incorporates a carefully-evolved spoiler profile, which
crucially reduces front-end lift. To balance this, the rear deck has been
re-shaped to incorporate an effective boot lid spoiler. The drag co-efficient,
0.36 in standard form, reduces to 0.35 with the optional lowered suspension
Sport Pack, a reduction of 5%, while lift is reduced by 28%. Lift balance
(front-to-rear difference) has been reduced by 55%.
STIFFER STRUCTURE
Intensive analysis of the MGF
body structure identified key improvements to body stiffness to seek ways of
adding to the improved chassis precision and ‘feel’ of the new TF.
On-road testing with accelerometer measurement was related to laboratory rig
testing and extensive computer modelling.
The resulting package of
improvements offers significant benefits in both measured and perceived
robustness. In addition to the solid mounting of both front and rear subframes,
the front subframe has a diagonal cruciform tubular brace on the underside,
linking its four-corners to the floor pressing of the underbonnet area.
The bracing behind the centre
fascia console from the floor tunnel to the substantial cross tube that carries
the steering column has been considerably strengthened. There are two bolt-on
tubular braces arranged in triangular form across the top of the engine bay.
Combined with the new, re-shaped and one-piece outer sill and rear wing
pressing, these items improve the torsional stiffness of the shell by 20%, and
reduce scuttle shake.
PEPPED-UP POWERTRAIN
The MG TF has a range of
four powertrain choices with even higher all-round standards of performance and
throttle response. At the top of the range, the TF 160 has a regular
production version of the Trophy’s high-output 1.8 VVC engine, developing the
same peak power of 160Ps (158bhp, 118kW) at an eager 6900rpm. This replaces the
former 145Ps (143bhp, 107kW) 1.8 VVC engine, and gains its extra power from
enhanced breathing.
There is a new low-loss intake
system with a larger throttle body, improved porting profiles and a low
back-pressure, dual mode exhaust system. The freer-flowing exhaust features
thin-wall catalyst technology and an electronically-controlled pneumatic valve
that optimises exhaust flow according to operating conditions. This retains
low-speed refinement while enhancing performance and characteristic sports car
sounds at higher speeds.
The efficiency of the new TF
160 unit is demonstrated by the way it combines increased performance (top speed
up from 130mph/209km/h to 137mph/220km/h) with reduced CO2
rating (down from 189 to 179g/km).
For the new core model in the
range, the TF 135, (replacing the 1.8i), a more powerful version of the
normal 1.8 litre engine has been developed. This uses TF 160-style
induction and exhaust systems plus high lift cams, bringing a power increase
from 120Ps (118bhp, 88kW) to 136Ps (134bhp, 100 kW). In addition, the engine ECU
has been re-mapped to optimise throttle response, and the VVC / TF 160
gear ratios have been adopted for improved in-gear performance. Against the
clock, the TF 135 is now creditably close to the former VVC model, with a
top speed of 127mph/205km/h.
In the new TF range, the
unique-in-class choice of a EmCVT sports auto cum six-speed ‘manual’
transmission, with steering-wheel shift controls, continues in the form of the
TF 120 Stepspeed. This retains the 120Ps (118bhp, 88kW) engine, and the
flexibility of either ‘normal’ or ‘sport’ fully automatic drive, plus a
sequential-change six-speed mode, controlled either by twin up/down toggles on
the steering wheel or via the centre floor lever.
The entry-level 1.6-litre version
of the MGF has proved popular since its launch in early 2001, making up
around one in eight of all MGFs sold, and this now has its equivalent in
the new TF 115 model. The sweet, short stroke 1.6-litre unit produces a
power output of 116Ps (114 bhp, 85kW), with a top speed up from 116mph/187km/h
to 118mph/190km/h, while also having a class-leading low CO2
rating at 169gm/km.
All the manual transmission
models benefit from an improved gearshift linkage, with a short-throw lever and
revised gear linkage geometry to reduce friction in the shift system for
enhanced gear selection.
SHARPER STYLE
MG Rover Group’s Product Design
Director, Peter Stevens, is deeply experienced in sports car design, having
worked on every type from Lotus Elan to McLaren F1. While retaining the
essential ‘modern classic’ character of the MGF, he and the design team
have given the MG TF a harder, more aggressive look, honed in the wind
tunnel for high-speed stability. The new front bumper/spoiler moulding has a
sharper, more emphatic treatment, with a full-width character line and a black
graphic framing the lower air intake, with its provision for ‘Fogstar’ fog
lamps.
Entirely new headlamp units, with
sleek silicon-protected polycarbonate covers, each house twin high-efficiency
70mm projector lamps, a sidelamp and a front direction indicator. A new upper
air intake design features a horizontal body-colour crossbar, while larger MG
badges are used front and rear.
In side profile, the MG TF
is lower and sleeker. A new sill and rear quarter design, now formed in a single
pressing, has a dart-like sill feature and more crisply shaped side air intake.
This new ‘monoside’ pressing does away with a panel seam under the door and has
a cleaner lower sill flange, as well as contributing 20% extra body stiffness.
Cooling air intake protection at
front and sides is a black hexagonal mesh, with a bright-finish option.
The new bootlid has a ‘cleaner’
top surface and an integral raised rear lip spoiler, stretching the visual
length of the car. Built into the spoiler lip is a new high-level brake lamp,
with fast-acting LED illumination. The tonneau panel finishers on each side have
been changed to an alloy finish, matching the admired fuel filler cap. In
harmony with the new front bumper, the new rear bumper has a distinctive feature
line and a black graphic surrounding the aperture for the new larger twin round
exhaust tailpipes. As on the MG saloons, the new MG TF rear lamp units
have clear lenses for the direction indicator and reverse light sections.
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