2006 Saab 9-3 Aero Features Six-Cylinder Turbo Power



9/05


2006 Saab 9-3 Aero Features Six-Cylinder Turbo Power

The Saab 9-3 Sport Sedan Aero with its new 2.8V6 Turbo engine is, quite simply, the fastest accelerating car ever to carry the Saab badge. It represents the culmination of almost 30 years' experience from Saab as acknowledged leaders in the art of turbocharging.

For the first time, Saab customers will be able to enjoy the combined benefits of turbocharged power and six cylinder refinement in a purpose-built package. With massive pulling power (350 Nm) spread widely across the engine's speed range, the 250 bhp/184 kW 2.8V6 Turbo generates more torque than most other six cylinder gasoline engine in the Saab 9-3 segment.

Saab Automobile Powertrain's expert knowledge and experience of turbocharging is recognized by its role as a Center of Expertise within General Motors for the development of turbocharged gasoline engines. The Swedish engineers were therefore closely involved during the conceptual design and development of GM's new global V6 engine architecture, ensuring it included the possibility of a turbocharged application.

Sophisticated technology

The 2.8V6 Turbo has a 60B: vee-angle between its cylinder banks for perfect balance and combines excellent multi-valve refinement with outstanding performance. The all aluminum construction provides a light and compact architecture, well suited to its transverse, front-wheel-drive installation in the Saab 9-3 Aero.

The cylinder heads, each with double chain-driven overhead camshafts operating four valves per cylinder, are of high specification aluminum and unique to this turbocharged variant. The design ensures enhanced heat resistance under 85 bar cylinder pressures, as well as minimum maintenance costs.

Also unique are pistons with hard anodized ring grooves for durability and under-skirt oil jet cooling, together with steel con-rods that are strengthened by sinter-forging, a process that involves molding metal in a powered form. The exhaust valves are filled with sodium to further enhance cooling. The cylinders have cast iron liners and a bore/stoke of 89.00 / 74.8 mm.

For improved engine breathing, variable cam phasing on the inlet side is electronically controlled and hydraulically actuated, allowing continuously variable adjustment through 50B: of crankshaft rotation. On the road, this translates to a more flexible power delivery and better fuel economy under different engine loads.

A die-cast aluminum oil sump is designed to increase structural stiffness and the strong, four-bearing crankshaft is made from micro-alloy forged steel, a specification more commonly seen in competition performance or diesel engines.

The twin-scroll, water-cooled TDO4-15TK turbocharger, operates at 0.6 bar maximum boost with intercooling and an integral by-pass valve. It is mounted centrally above the transmission and fed by both banks of cylinders. The use of two separate inlet tracts, one for each cylinder bank, separates the exhaust gas pulses, improving gas flow, reducing energy losses and raising turbocharger efficiency. The turbine wheel is made from a special high-grade steel alloy, commonly used in the turbocharged engines of world championship rally cars, which is resistant to erosion, cracking and creeping under high temperatures and centrifugal forces.

Also unique are double-skin exhaust manifolds, which are hydroformed with stainless steel liners to improve cold start emissions by minimizing heat absorption to the manifold. Air injection into each manifold for up to 30 seconds after a cold start also helps the central pre-catalyst, positioned upstream of the main catalytic converter, achieve 'light off', its effective working temperature, as early as possible.

Smart engine management

The 32-bit engine management system, with software calibrated specifically for the Saab 9-3 application, utilizes a torque-based engine control strategy and direct coil-over-plug ignition with a robust engine-mounted control unit. Ignition timing, fuel injection, turbo boost pressure, air mass measurement and the throttle setting are all key engine functions controlled by the software.

The sophisticated control strategy is designed to deliver smooth performance in all driving conditions. The system works with the vehiclebs transmission to modulate torque, providing stirring performance and excellent engine response. The system can also limit torque in low-traction conditions, helping provide confident, sure-footed driving. Variable fuel pressure further contributes to smooth idle and driving characteristics.

For driving comfort, control of the electronic throttle through the movement of the accelerator pedal is programmed to be sensitive to different driving conditions, with greater pedal movement introduced at lower vehicle speeds, such as when maneuvering or parking. At low engine speeds, the engine control system also brings the turbo in quickly by momentarily opening the throttle slightly more than requested by the driver.

On the road the new 9-3 Aero 2.8V6 Turbo packs a formidable punch and the driver will also immediately appreciate the smooth power delivery, like an iron first in a velvet glove. Apart from the boost gauge in the dashboard, the only clue to the presence of a turbocharger is an uncannily effortless rate of acceleration.

Pick-up from tick-over at just 720 rpm is instant, due to the engine's relatively large multi-cylinder capacity. At about 1,000 rpm, the turbo begins to build a massive wall of torque that is already in place by the time the tachometer swings through 2,000 rpm. It endows the 9-3 Aero with a level of performance never before seen in a Saab car.

Maximum torque is generated all the way from 2,000 rpm to 4,500 rpm, with 90 per cent of this value available at an exceptionally low 1,500 rpm. Careful programming of the engine management software means that under a full throttle load, from take-off or low engine speeds, 90 per cent of maximum acceleration is delivered within one second.

The zero to 60 mph dash is accomplished in just 6.9 seconds, but in-gear acceleration provides even more impressive evidence of this engine's outstanding elasticity. In top gear, the transition from 50-95 mph can be accomplished in just 8.3 seconds, a figure that places the 9-3 Aero among the very best in its class.

The fun-to-drive nature of this performance is also matched by an exhilarating engine note that can be heard inside and outside the car. This has been achieved by tuning the twin sports exhausts downstream of the main catalyst. It gives the new Saab 9-3 Aero a distinctive aural, and visible character in keeping with its position as the sporting flagship of the range.

The engine is offered in the 2006 Saab 9-3 Aero Sport Sedan, SportCombi and Convertible with a choice of six-speed manual or automatic transmissions. The close-ratio manual gearbox includes duel output shafts to reduce transmission vibration, together with a dual mass flywheel this ensures smooth and refined performance.

The 'smart' Aisin AW automatic transmission is adaptive to driver usage patterns and prevailing road conditions. It can sense changes in engine performance, engine load, road gradient and altitude, quickly finding the right gear without an irritating 'hunting'.

For closer driver involvement, Saab Sentronic, a sequential manual gearshift, is also included. When the shift lever is moved across the gate to bmanualb Sentronic mode, bupb and bdownb changes can be made with full lock-up in 3/4/5 or 6th gears. This process is taken a step further by the option of steering wheel buttons, which bring gear-shifting right to the fingertips of the driver.

Overall, the 2.8V6 Turbo generates class-leading levels of torque with a seamless, turbine-like power delivery. It combines the inherent advantages of a six-cylinder engine - refinement and a rapid throttle response - with the effortless, torque-boosting properties of turbocharging.


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