GM's Global V-6 Family Expands With New 2.8L Turbocharged Engine

General Motors expands the family of advanced global V-6 engines with the sophisticated 2.8L V-6 Turbo -- a transverse-mounted compact and lightweight powerhouse that delivers the performance of a larger-displacement engine.

The 2.8L V-6 Turbo debuts in the Aero models of the all-new Saab 9-3 SportCombi, Sport Sedan and Convertible, continuing the brand's heritage of turbo power established in 1977. It is the most sophisticated turbocharged engine ever offered in a Saab vehicle, delivering excellent responsiveness through low-speed torque and high-rpm power, as well as exceptional refinement.

Technology such as a twin-scroll turbocharger and variable intake valve timing helps the 2.8L V-6 Turbo achieve 250 horsepower (184 kw) and 258 lb.- ft. of torque (350 Nm) in the 9-3.

"The 2.8L V-6 Turbo has a strong, linear feel that gives the impression of a larger-displacement engine," said Tim Cyrus, global V-6 chief engineer. "The feeling of power is tremendous, but so is the smoothness and refinement built into the engine."

Developed in conjunction with other engines in the global V-6 family, turbocharging was designed into the architecture's structural parameters. The powertrain engineers' experience with turbocharging at Saab was integral in refining the engines' performance, with the 2.8L V-6 Turbo delivering maximum torque by 2000 rpm and maintaining it through 4,500 rpm. Ninety percent of peak torque is available from just 1500 rpm. This broad performance spectrum results in an engine that effectively offers two torque curves: a linear curve that delivers exceptional low- and mid-range torque, and higher-rpm power that benefits from the pressure of the turbocharger.

"It's almost like having two engines on tap," said Cyrus. "At low speeds, the inherent torque of the V-6 pulls strongly, but it has the power of a larger-displacement engine when the full power of the turbo system is called up."

Inside the engine

All engines in the global V-6 family share traits that include a lightweight aluminum cylinder block with iron cylinder sleeves, an aluminum structural oil pan and aluminum cylinder heads with four valves per cylinder. The 2.8L V-6 Turbo builds on those strengths with components and technology developed specifically for the turbo system, including:

* Twin-scroll turbocharger delivering approximately 9 pounds of boost (0.6 bar)

* Integrated charge cooling

* Unique cylinder heads made from 356T-6 aluminum and featuring sodium- filled exhaust valves

* Forged steel crankshaft and sinter-forged connecting rods strengthened for turbocharged loads

* Pistons with anodized ring grooves designed for turbocharger boost pressure

* 9.5:1 compression ratio

* Piston oil cooling jets

* Unique camshaft profiles designed for turbocharger performance

* Hydroformed "dual skin" exhaust manifolds with stainless steel inner liners

* Engine-mounted oil cooler

The turbo system features a unique, twin-scroll turbocharger. It has an integral bypass valve and is fed by two exhaust ducts -- one from each cylinder bank. Separating the exhaust gas pulses with two compressor zones improves gas flow and reduces energy loss. The turbo system's charge cooler promotes performance by reducing the temperature of inlet air.

Additionally, the 2.8L V-6 Turbo employs a conventional, single-stage intake manifold and variable valve timing on the intake camshaft -- the variable valve timing helps optimize performance and emissions control. Also, a variable fuel pressure system helps ensure smooth idle and driving characteristics. Valve timing and fuel pressure are managed by the engine's powerful controller, a 32-bit micro-hybrid system which is calibrated specifically for the turbocharged application.

The sophisticated controller operates under a torque-based engine management strategy designed to deliver smooth performance in all driving conditions. The system works with the vehicle's transmission to modulate torque, providing stirring performance and excellent engine response. The system also can limit torque in low-traction conditions, helping provide confident, sure-footed driving.

Cross-globe connection

The 2.8L V-6 turbo is the third variant of the new global V-6 family -- a technologically advanced 60-degree, dual overhead-cam architecture designed to produce strong power and excellent fuel economy to meet different needs in markets around the world. Engineers from GM Powertrain in North America and FGP -- the Europe-based Fiat-General Motors Powertrain consortium -- as well as Holden collaborated on the development.

The global V-6 engine family also includes a 2.8L V-6 VVT normally aspirated version which debuted in the 2005 Cadillac CTS, as well as a 3.6L V- 6 VVT version that also is available in the CTS. The 3.6L V-6 VVT also is available in the 2005 Cadillac STS and SRX, as well as the Buick Rendezvous and LaCrosse. It is available under the Alloytec brand name in the 2005 Holden Commodore, Calais, Berlina short wheelbase, Statesman and Caprice long wheelbase, Ute, Cab Chassis and Crewman. All use variable valve timing for optimal performance and emissions control.

The 2.8L V-6 Turbo is built at Holden's Port Melbourne, Australia facility, along with 3.6L variants of the global V-6.

SOURCE General Motors Corporation

Nick Richards of GM Powertrain Communications, +1-248-857-0163, Email: nick.richards@gm.com

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