06
March
2012
|
00:00
Europe/Amsterdam

Gt86 press kit: excellent power-to-weight ratio and perfect balance

  • Comprehensive weight saving measures for a total vehicle weight of only 1,239 kg
  • Ultra-low centre of gravity —just 460 mm
  • Ideal, 53:47 weight distribution for excellent response to even subtle steering, throttle and brake inputs
  • MacPherson front strut and rear double wishbone suspension systems fine-tuned for direct handling feel, instant response and superb controllability
  • Advanced, three mode Vehicle Stability Control (VSC) incorporating a new VSC SPORT mode
  • Fitted with Prius tyres to exploit the maximum potential of the chassis and suspension

The GT86's unique powertrain format combines with the world's most compact four-seat sports car design, light weight, low inertia and a low centre of gravity for the best possible power-to-weight ratio.

Fine-tuning of the GT86's suspension, brakes and steering has maximised the benefits of its minimal mass, supercar-rivalling lack of inertia and ultra-low centre of gravity, allowing drivers to fully exploit the purity of the new Toyota sports car's outstandingly nimble handling, dynamic agility and cornering poise.

The Nurburgring played a particularly important role in helping chief test driver Akihiro Osaka and his team test and tweak the vehicle. Osaka's approach was to alternate testing between the track itself and the surrounding country roads, thus realising both the durability necessary for endurance racing and the handling to full engage drivers during everyday use.

Comprehensive Weight Saving Measures

Weight saving was fundamental to the development of the GT86. Making it lightweight was synonymous with honmono kan making it authentic. Only a genuinely lightweight machine offers the intimacy and involvement of a car that can be driven as if it were an extension of the driver's body.

A car with a 2.0 litre engine of this class is normally about 1,300 kg, but Toyota was determined to make the GT86 weigh around 1,200 kg, guaranteeing an excellent power-to-weight ratio.

It was decided that the key to minimising weight was to maximise the use of specialised, exclusive parts, through a 'Common Parts Reduction Campaign'. For instance, the common fuel tank used initially was replaced with a model-specific design which has a particularly unusual shape in order to fit the space available.

Ultimately, this policy lead to a reduction in the usage of common parts in the GT86 to just 9%.

Establishing the correct body rigidity is also a delicate balance between performance and weight gain. Increasing strength in some areas but actually decreasing it in others to strike the right balance, the body engineers adopted high tensile sheet steel widely throughout the bodyshell to combine light weight with efficient impact absorption and optimum torsional stiffness.

980 MPa high tensile steel has been adopted for areas such as the roof side rails, front header and centre pillar reinforcement, and 1,500 MPa grade hot-pressed steel used for the roof centre reinforcement. The adoption of a 'pagoda' roof form gives extra torsional stiffness to the structure, whilst allowing it to be fabricated in steel just 0.65 mm thick, to minimise weight.

The bonnet is fabricated in sheet aluminium, and an innovative front wing design has enabled thinner sheet steel to be used in the construction process. In combination, these comprehensive weight saving measures have resulted in a vehicle weight of only 1,239 kg.

Ideal Weight Distribution

The flat-four format of the front-mounted boxer engine combines with the lowest driver hip-point of any Toyota production vehicle -just 400 mm- to give the GT86 an ultra-low centre of gravity of only 460 mm.

Both the powertrain and driving position have been set as low and as far as possible towards the centre of the vehicle to optimise balance, giving the GT86 an ideal, 53:47 weight distribution.

Toyota engineers established that, during spirited driving, a 53:47 front bias produced the ideal response to even subtle steering, throttle and brake inputs, allowing drivers to readily control dynamic weight distribution for the best possible vehicle behaviour.

Suspension Fine-Tuning

Incorporating a front performance rod and front and rear anti-roll bars, the front MacPherson strut and rear double wishbone suspension systems have been fine-tuned to react instantly to driver input, with a direct handling feel, sharp response and superb controllability.

A new MacPherson strut front suspension layout has been adopted, maximising the benefits of the low centre of gravity and low inertial properties inherent in the GT86's powertrain. Allied to stiffer mounting points, the system features a newly designed upper support, shock absorber, coil spring, stabiliser, knuckle, lower arm and cross member.

The L-shaped lower arm has been reverse positioned to allow the engine to be mounted as low and as close to centre of the vehicle as possible. The steering gearbox has been positioned behind the cross member. The cross member itself has been specially designed to fit within the limited space between the oil pan and the exhaust pipe. Further lowering the GT86's centre of gravity, the coil springs and strut mounts have been positioned as low as possible.

The GT86's 23 N/mm front spring rates allow for slight body roll on initial turn-in, creating the perfect relationship between steering feel and vehicle behaviour exhibited by a classic front-engined, rear-drive platform.

The rear, double wishbone suspension system offers the ideal combination of stability, grip and driver feedback. It also features stiffer mounting points, as well as a newly designed sub frame, shock absorber, coil spring, lower arm, stabiliser and trailing link.

The differential opening of the subframe has been made larger, reducing system weight. The cross sections of the differential opening have also been enlarged to maximise rigidity. The rigidity of the body and subframe attachment points has been enhanced, minimising weight increases whilst ensuring optimum grip and stability performance. The roll axis has been tuned to compliment the front suspension whilst still maintaining the high roll rigidity expected of a sports car.

Electric Power Steering

The GT86 is fitted with a column-coaxial electric power steering system, offering drivers a quick, direct and accurate steering feel. The wheel can be adjusted for rake through 15 mm and for reach through 20 mm. The particularly low, 16 degree column tilt angle is essential for compatibility with the GT86's ultra-low driver hip point.

The steering system was developed for high rigidity from the steering column to the gear box and has a particularly quick gear ratio - 13:1.

Braking and Stability Control Systems

Ventilated disc brakes to both front - 294 mm - and rear - 290 mm- wheels offer a different brake pedal feel to that of any other Toyota. Brake response to pedal input has been fine-tuned to provide precise modulation, assisting drivers in car control finesse by allowing for the smoothest possible dynamic weight transfer under braking.

The GT86 is equipped, as standard, with an Anti-lock Braking System (ABS), Electronic Brakeforce Distribution (EBD), Traction Control (TRC) and an advanced, three mode Vehicle Stability Control (VSC).

The ABS and switchable VSC safety systems have been specifically tuned to combine dynamic stability at the limit of the vehicle's performance envelope with minimal electronic intrusion on the purity of the driving experience.

The new VSC system features an additional, next generation VSC SPORT mode. When selected via a transmission tunnel-mounted switch, VSC SPORT expands the permissible range of lateral acceleration and movement before the system intervenes, allowing the driver to explore the limits of vehicle dynamics without sacrificing stability.

Both TRC and VSC may also be fully disengaged by pushing and holding the VSC switch for more than three seconds.

Wheels and Tyres to Exploit Dynamic Potential

Paying tribute to the legendary Black Racing wheels of the AE86, The GT86's 17" alloy wheels feature a unique centre hub design. Toyota's traditional centre cap diameter is 60 mm, but this has been reduced to 49 mm, saving weight for no loss of rigidity, whilst making the spokes appear longer, and the wheels larger.

Toyota engineers determined that the dynamic potential of the GT86 should not rely on high-performance tyres, and the new sports car is equipped with identical 215/45 R17 tyres to those fitted to the Prius.

With very neutral, predictable properties, these tyres allow drivers to exploit the maximum potential of the chassis and suspension. Engineering the GT86 to handle well on Prius tyres also ensures that customers who upgrade to higher performance tyres will readily appreciate the net performance again.