SUBARU WRX STI
- Iconic STI is latest generation of Subaru’s high performance legend
- Handling, ride, steering and turbo power are traditional WRX hallmarks
- Symmetrical All-Wheel Drive and 2.5-litre turbo Boxer engine
- Tremendous value
WRX and STI. Two groups of three letters that mean a huge amount to generations of performance enthusiasts, ever since Subaru’s all dominating Impreza rally cars ruled the special stages of the 1990s and 2000s.
Today’s Subaru WRX STI is a continuation of an enduring legend. An icon that builds on generations of Boxer engine and Symmetrical All-Wheel Drive technology, rewarding drivers, providing great reliability, offering incredible turbocharged performance and an extremely affordable price tag.
The WRX STI comes with a 2.5-litre 300PS version of the Boxer engine and traditional STI styling features such as a bonnet scoop and large rear spoiler, but in a more sophisticated evolution.
Under the skin, the WRX gets the ultimate evolution of Subaru’s Symmetrical All-Wheel Drive technology, giving the car unprecedented levels of performance and traction. Agility and driving enjoyment are further enhanced by the car’s low centre of gravity, new hydraulic steering and a re-worked, short-throw gear shift.
The engineering brief for the new WRX STI was to develop a car that provided absolute power and driver control. With 300PS and 407Nm of torque on offer from the engine, and a drivetrain that allows the car to apply the maximum power and torque to the road at all times, the WRX STI is one of the fastest – and safest – performance cars in ‘real world’ conditions.
Its hydraulic power steering has been engineered to not only give more feel from the driver’s seat, but also even quicker turn-in.
Its suspension system improves ride comfort without sacrificing the handling characteristics that have made previous generations of WRX STI so successful on road, stage and track. A stiffer body shell and advanced powertrain management system give greater grip, helping active safety.
Coupled to high equipment levels, leather and Alcantara clad sports seats and a race-derived D-shaped steering wheel, the interior of the WRX STI has the right combination of comfort and visual drama.
As well as its striking styling, the body shell of the new WRX STI incorporates a higher percentage of ultra-high tensile steel. This has resulted in a body that is 140 per cent stiffer than the previous model, yet with no increase in weight.
The additional stiffness minimises chassis flex, improves steering response and enables greater suspension refinement.
In styling terms, the front end has Subaru’s trademark hexagonal grille, now in gloss black, while its LED headlamps and lower front fog lamps highlight the low stance.
The bonnet scoop, a feature of the WRX STI’s predecessors, is closer to the front and embedded into the bonnet, reducing height while improving aerodynamic efficiency and pedestrian-impact crash performance.
The base of the A-pillar has moved forwards by 200mm to give a more coupe-like profile, enhanced by a lower roofline and shark fin radio antenna.
Squared-off wheel arches, featuring vents behind the front wheels, add to the solid appearance and manage air-flow around the car.
At the rear, four exhaust pipes and an integrated black diffuser are incorporated into the bumper, emphasising the low centre of gravity, set off by a rear spoiler that’s 8mm higher than that the previous generation, improving rear visibility from the driver’s seat. The drag co-efficient of the spoiler remains the same and weight is reduced by 0.3kg.
The performance of the WRX STI is matched by the sporting appeal of its interior. A small-diameter, D-shaped steering wheel adds a race-inspired touch, while sculpted front sports seats, with embossed ‘STI’ logo on the head restraints, are finished in Alcantara with leather side bolsters.
There are further red highlights on the upholstery, while stainless steel sill plates, additional red lighting elements and carbon fibre-look trim on the centre console enhance the performance car feel.
At the same time, all the controls have been designed to be simple and intuitive to use. The instrument binnacle has a dual-dial layout with 3.5-inch full-colour LCD screen, with dials backlit in red with white needles.
A new Multi-Function Display (MFD), unique to the WRX STI, is positioned at top-centre of the dashboard to allow drivers to monitor the car’s performance functions and capabilities.
The 4.3-inch LCD colour screen displays a number of functions for everyday driving, with separate screens for audio, calendar and clock, fuel economy, active safety and status of the All-Wheel Drive system, outside temperature and vehicle health check.
Unique within the Subaru range, the MFD in the WRX STI offers an additional boost gauge screen option, providing analogue and digital representations of the accelerator opening, current boost pressure and boost pressure peak value. This can heighten driving enjoyment and is useful for those owners who will take their car on track.
Chassis and running gear
The suspension and running gear of the WRX STI are designed to improve driver satisfaction, steering feel and braking performance.
The front suspension is fully independent and uses MacPherson struts with enhancements to improve damping control, steering response, agility and ride comfort.
There are stiffer cross members and control arm bushes for more linear steering response, improved handling and reduced noise. A thicker front anti-roll bar reduces roll and improves stability, while the front suspension’s transverse link rear bushes are mounted 10mm lower to improve ground contact for the front inner wheel under cornering, further improving traction and stability.
The WRX STI’s fully-independent rear suspension features a thicker anti-roll bar, stiffer sub frame bushes and new rear sub frame supports to improve stability and steering response. Lowering the sub frame front mounts for the suspension’s lateral links has added 3mm of initial toe-in, generating quicker lateral force for improved steering response. The shock absorber mounts have been moved outwards by 10mm to provide improved damping.
The WRX STI continues to employ a hydraulic power steering system to provide a high level of steering feel to drivers. For right-hand drive models sold in the UK, the new steering system offers improved turn-in, with 15 per cent quicker ratios than the previous model (altered from 14.8 to 12.7). The steering torsion bar in the new model is 125 per cent stiffer than the previous version’s, further improving response and feel.
Modifications to the suspension ensure the new WRX STI is more agile than ever before, generating lateral G-force just 0.1 seconds after turning. This is half as much G-force lag as a Volkswagen Golf GTI (0.2 seconds) and on-par with the Porsche 911 Carrera S against which the WRX STI was benchmarked dynamically throughout its development.
The WRX STI employs the same 17-inch Brembo disc brakes as the previous model (four-pot callipers on the front and two-pot callipers on the rear). The brake booster has been tuned to provide quicker brake response and the master cylinder has been enlarged by seven per cent to increase braking power.
The more responsive brakes are housed in new 18-inch alloy wheels which are 15 per cent stiffer than those found on the earlier model and each 1kg lighter. The new wheels achieve a greater balance between reduced weight, component strength and reliability, and aerodynamics. The WRX STI is equipped with custom-made 245/40 R18 high-performance Dunlop SP Sport Maxx tyres.
The WRX STI takes one of Subaru’s signature features to the max. The legendary Symmetrical All-Wheel Drive (AWD) system has a centre differential, which allows drivers to exploit its high levels of traction, stability and agility.
Combined with manual transmission and a viscous limited-slip differential, the basic torque distribution is set at 50:50 front to rear – should a front or rear wheel slip, the viscous coupling adjusts the torque distribution to optimise traction. The system employs a torque vectoring system to further improve traction and grip at front and rear.
In the previous-generation STI, the centre diff operated in one of two modes, manual or auto. The new model gives the driver a manual mode plus three pre-set automatic modes to choose from, according to road or track conditions and driver preference.
‘Auto’ Mode, the default setting, provides the best balance between agility and traction for everyday driving conditions. ‘Auto+’ Mode limits torque in order to improve traction on slippery road surfaces and when stability is most important. ‘Auto-’ Mode increases steering responsiveness and allows more torque to be distributed to the rear of the car, allowing a greater degree of agility and throttle adjustability.
Three-mode SI-Drive system
The WRX STI benefits from a custom driving mode system, Subaru Intelligent Drive (SI-Drive), which allows drivers to select one of three modes to alter engine and throttle response.
Intelligent (I) Mode carefully monitors driving conditions to deliver fuel efficiency and smooth power delivery. Sport (S) Mode is the most versatile for all conditions, offering linear power across a wide range of engine speeds, with slightly more urgent throttle response than I Mode. Sport Sharp (S#) Mode allows drivers to extract the maximum response from the 2.5 litre Boxer engine, with more direct throttle response and closer, more precise rev control across all engine speeds.
Engine and transmission
Under the bonnet, the new WRX STI is fitted with an evolution of Subaru’s 2.5-litre horizontally-opposed Boxer engine. The revised unit retains the proven benefits of the horizontally-opposed layout, but is more efficient with sharper responses.
Generating 300PS at 6,000rpm and 407Nm torque at 4,000rpm, the engine enables the WRX STI to reach 62mph from standstill in 5.2 seconds, with a 159mph top speed. It returns fuel economy of 27.2mpg on the combined cycle, has CO2 emissions of 242g/km and is Euro6 compliant.
Changes to the engine over previous generations include a larger intercooler to improve cooling efficiency and modifications to the ECU to enable more precise tuning of boost pressure control, reducing turbo lag and improving acceleration response.
As a result, when accelerating at 40mph in third gear in S Mode (using the SI-Drive mode controller), the WRX STI can accelerate at 2.0m/s2 after just 0.5 seconds, compared to 0.9 seconds on the previous generation. In the same gear, forward acceleration also now peaks at 3.2m/s2, compared with 2.5m/s2 in the previous model.
The unit is fitted with Subaru’s dual intake and exhaust Active Valve Control System (AVCS), which enhances efficiency and improves acceleration response by varying the valve timing to provide optimum air flow in and out of the engine. AVCS optimises torque between 2,000 and 4,000rpm, the engine speeds typically used by owners on a day-to-day basis, and improves acceleration response at higher engine speeds.
To ensure the engine complies with Euro 6 emissions standards, a new secondary air system introduces recycled warm air to the exhaust port of the cylinder head. This reduces hydrocarbon emissions when the engine is started by reigniting any unburned fuel and helping the catalytic converter to start working earlier.
Six-speed manual gearbox
The WRX STI has a six-speed manual gearbox as standard. Compared to the older model, it has a shorter throw and improved NVH performance.
In addition to producing a sportier gear change, revised scissor gear springs reduce the level of noise from the gearbox and lessen vibrations through the unit.
Practicality and packaging
It may be a performance car at heart, but the WRX STI retains the practicality required for everyday life.
The car’s lengthened wheelbase (up 25mm to 2,650mm) and improved packaging are key to delivering greater spaciousness than ever, though it has grown by only 15mm in length, to 4,595mm. Width stays the same at 1,795mm, but the side sills have been lowered by 20mm and pushed outward by 15mm, freeing up more space in the cabin, which is now 15mm wider.
The roof height is reduced by 5mm to 1,465mm, increasing aerodynamic efficiency and lowering the side profile.
By moving the A-pillars forward by 200mm compared with the previous model, the WRX STI has a greater sense of spaciousness upfront. Combined with a lower instrument panel, the repositioned pillars improve the driver’s field of view.
Extending the wheelbase created more space for rear passengers, with more leg, shoulder and elbow room. A raised hip point – up 20mm – improves the feeling of space in the rear and makes it easier to get in and out.
The driver’s seat has been redesigned to maximise comfort and visibility, and to increase support during more spirited driving. With bigger bolsters and higher, firmer thigh supports for greater support under cornering. The seat springs have been tuned to evenly distribute pressure throughout the seat, while new lumbar supports make it easier to find the ideal driving position.
The cabin design gives a generous level of storage space. Four large door pockets hold bottles easily, while greater provision has been made for smaller items, such as wallets, smartphones and music players, with a large central storage tray, covered centre console box and larger armrest storage.
Furthermore, cargo capacity is increased by 40 litres to 460 litres, while a 60/40 split-fold rear seat folds forward to create an almost flat load bay.
For over 20 years, Subaru customers have loved the technical supremacy of the STI range of vehicles and to enhance that proposition, WRX STI will be available with mobile WiFi from EE until the end of June 2017.
The mobile in car system allows multiple devices to be connected to WiFi on the move with 30GB download allowance and a large enough battery for 24 hours of streaming, perfect for keeping road trip passengers entertained.
The all-steel unitary structure of the Subaru WRX STI is engineered to deliver the highest level of crash safety performance while also providing a comfortable ride and a high level of refinement.
Active safety features
Subaru’s ESP-equipped Vehicle Dynamics Control (VDC) system, complements the superior stability of Symmetrical All-Wheel Drive and is standard on the model. Its multi-mode VDC system was developed to provide world-class hazard avoidance capability. The operational status of the VDC is displayed on the Multi-Function Display.
VDC has been refined to cut yaw more efficiently during extreme cornering and also operates the emergency brake assist system. This system assesses the need for braking assistance according to the force applied by the driver and the speed at which the brake pedal is pressed. The result is almost identical braking performance on wet and dry surfaces.
The WRX STI allows owners to switch off both the multi-mode VDC and Traction Control System (TCS), making the car more effective on track. By selecting ‘Traction’ mode, the torque vectoring system remains engaged, but drivers are able to deploy maximum engine power without electronic intrusion.
Other measures to improve active safety include improved forward visibility, achieved by moving the base of the A-pillars forward by 200mm and lowering the dashboard top. Thanks to the use of ultra-high tensile steel, the A-pillars are thinner than those on the previous-generation car, further improving visibility. Rear visibility is also improved by wider door mirrors and a larger rear spoiler, which gives a clearer view of the road behind.
Passive safety features
For maximum impact resistance, the WRX STI body shell is equipped with a series of ring-shaped reinforcement frames joining the A-, B- and C- pillars with cross members at the roof and floor.
The new WRX STI has a higher proportion of ultra-high tensile steel for sections of the bodyshell, achieving a 140 per cent increase in torsional rigidity without adding to overall weight. The stronger steel is used to reinforce the front crash structure, side sill and A-pillar, which are the main structural parts of the cabin; the B-pillar, for greater side impact protection; and along the roof rail, to improve occupant protection in the event of impact on the roof. The side of the car also features high-strength cross members, helping minimise deformation in the event of a side collision.
Pedestrian protection is enhanced thanks to a higher proportion of energy- absorbing materials inside the engine bay and repositioning the bonnet scoop closer to the nose of the vehicle.
Inside, stiff seat frames with tall backrests and separate energy-absorbent headrests help reduce whiplash forces and minimise injury. In the rear seats, the cushion shape is designed to hold adult occupants firmly in place, with two ISOFIX anchors fitted for child safety seats.
Front, side and curtain airbags are fitted as standard, as well as a new knee airbag which cushions the driver’s legs in the event of a collision.
Other features enhancing occupant protection include a retractor mechanism for the brake pedal; a collapsible steering column; and a separation mechanism between the bodyshell and steering column to minimise the forces generated by the steering wheel pressing against the driver’s torso in a serious collision.