2008i 2.8L V-6 Turbo (LP9)

2008i Model Year Summary

            • Twin-impeller turbocharger

            • Unique double-wall exhaust manifolds

            • Engine-mounted oil cooler

            • Robust 356T-6 aluminum cylinder heads

            • Air-to-air intercooler

·         Improved horsepower from 250 to 280 HP

Revised engine calibration with increased turbo boost pressure

Carryover features and benefits from 2007 model year

TURBOCHARGED VARIANT  FOR GLOBAL V-6 FAMILY

As the third variant of GM’s sophisticated global V-6 engine family, the 2.8L V-6 Turbo began in the Aero models of the all-new 2006 Saab 9-3 SportCombi, Sport Sedan and Convertible. It features a high-efficiency twin-impeller turbocharger and features high specific output as well as a broad torque band to deliver the performance of a larger-displacement engine. The improved LP9 model makes its debut in 2008i in the Saab Turbo X Sedan and Sport Combi

TWIN-IMPELLER TURBOCHARGER

The turbocharger housing uses two impellers fed by a unique dual inlet chamber from the exhaust manifolds on each cylinder bank. A single compressor feeds pressurized air into the fixed volume intake manifold. This design takes the most advantage of the exhaust pulse energy for quick throttle response and smooth power increase.

UNIQUE DOUBLE-WALL EXHAUST MANIFOLDS

Special exhaust manifolds made of two steel pipes, one inside the other, lead to the double-duct turbocharger housing. There is an air gap between the inner and outer pipes, to insulate heat and noise.

ENGINE-MOUNTED OIL COOLER

An engine-mounted oil cooler is attached to the left side of the engine block to promote the longevity of the oil.

ROBUST 356T-6 ALUMINUM CYLINDER HEADS

The cylinder heads are constructed of stronger 356T-6 aluminum to ensure durability with the additional heat generated by the forced induction of the turbocharger.

AIR-TO-AIR INTERCOOLER

To lower the temperature and increase the density of the intake air, an air-to-air intercooler is incorporated into the intake air system.

Overview

The 2.8L V-6 Turbo was introduced for the 2006 model year simultaneously in North America for the Saab 9-3 and in Europe for the Saab 9-3 and Opel Vectra. The 3.6L V-6 VVT was the first engine in GM's sophisticated, global V-6 engine family and debuted in 2004. A naturally aspirated 2.8L was added for 2005. The global V-6 architecture was jointly developed by GM technical centers in Australia, Germany, North America and Sweden. The engine's design is based on the philosophy that a true family of global engines provides the best value and performance for the customer and the best return on investment for General Motors. The engines apply the most advanced automotive engine technology available, from state-of-the-art casting processes to full four-cam phasing to ultra-fast data processing and torque-based engine management. Each

delivers a market-leading balance of good specific output, high torque over a broad rpm band, good fuel economy, low emissions and first-rate noise, vibration and harshness control, with exclusive durability enhancing features and very low maintenance.

The turbocharged 2.8L has a slightly reduced compression ratio of 9.5:1 versus 10.0:1. The sand-mold-cast block features strong cast-in iron bore liners, six-bolt main caps, and inter-bay breather vents.

Like the earlier Global V-6 engines, double overhead cams, four-valves-per-cylinder heads with silent chain valvetrain continue to contribute to the V-6 Turbo’s smoothness and high output. The silent chain drive operates with less noise due to an inverted tooth design that spreads out the period of engagement between the sprocket and chain. By lengthening the period of contact between the sprocket and chain, the force of the initial impact between the two is reduced because it is spread out over a longer time period. Therefore, the noise created by the initial sprocket/chain impact is significantly reduced. The result is much quieter and smoother sprocket-to-chain engagement, and that makes for a smoother and quieter engine.

The 2.8L V-6 Turbo employs cam phasing for variable valve timing to change the timing of intake valve operation as operating conditions such as rpm and engine load vary. The result is linear delivery of torque, with near-peak levels over a broad rpm range, and high specific output (maximum horsepower per liter of displacement) without sacrificing overall engine response and drivability.

The V-6 Turbo uses electro-hydraulic vane-type phasers to rotate the intake camshafts relative to the cam-drive sprockets. The variable valve timing system was developed for maximum durability and outstanding noise, vibration and harshness control. It is virtually impervious to particles or contaminants in the engine oil and minimizes the chance that the phasers can stick, even in the most demanding operating conditions. The phasers adjust cam timing quickly and seamlessly for optimum performance, driveability and fuel economy.

Aluminum-intensive construction extends to the V-6 Turbo’s pistons, which are cast aluminum and feature full floating wristpins. Finally, the global V-6 engine family was developed with pressure-actuated oil squirters in all applications. Three jet assemblies in the block each hold a pair of oil-squirting jets that drench the underside of each piston and the surrounding cylinder wall with an extra layer of cooling, friction-reducing oil. The jets are activated when oil pressure reaches a prescribed level. They reduce piston temperature, which in turn allows the engine to produce more power without reducing long-term durability. Moreover, the extra layer of oil on the cylinder walls and piston skirts further dampens noise emanating from the pistons, meaning quieter operation.

The V-6 Turbo’s durability enhancing features included a polymer coating applied to the piston skirts. This high-tech coating was developed to withstand the heat and friction generated by piston movement in the cylinder, and it allows tighter piston-to-bore clearances without bore scuffing. The polymer coating extends the benefits of the floating-pin piston and rod assembly and further reduces noise generated by the piston’s movement within the cylinder. The coating also helps limit bore scuffing, or abrasion of the cylinder wall over time from the piston’s up-down motion. The net result is a quieter, more durable engine.

The strength of a forged steel crankshaft ensures the durability required of high output variants of the global V-6 engine family, and it adds an extra level of robustness in the 2.8L Turbo engine. The V-6 Turbo’s connecting rods are manufactured of sinter-forged steel. Sinter-forging is considerably more expensive than conventional casting or wrought forging. Yet because parts are manufactured with much greater precision, they require less machining, and both machine tooling costs and manufacturing time are reduced. Overall assembly efficiency – and quality – increases.

The 2.8L V-6 Turbo’s sequential fuel injection manages fuel pressure at the injectors and eliminates a fuel return line from the engine to the fuel tank. This “returnless’’ injection – also known as a demand system – improves performance and greatly reduces emissions. It is one of

the most efficient fuel-delivery systems in production and, true to the V-6 VVT global development philosophy, provides the foundation for several fuel-injection variants that can be tailored to market demands or legislative mandates without extensive re-engineering. The vehicle fuel tank has a variable pressure supply pump which regulates fuel pressure between 3 to 5.5 bar which improves the dynamic range of the fuel system this fuel pressure is regulated by a fuel pressure sensor on the fuel rail

All of the global V-6’s fuel delivery components, from the fuel pump to the delivery line to the injectors, have been developed to minimize operational noise. The fuel rail is fitted with an internal fuel pressure damper, which virtually eliminates harsh pressure pulses.

Electronic “drive-by-wire” throttle eliminates a mechanical link between the accelerator pedal and throttle plate. The global V-6 has no throttle cable; instead, a potentiometer at the pedal measures pedal angle and sends a signal to the ECM; the ECM then directs an electric motor to open the throttle at the appropriate rate and angle. Electronic Throttle Control (ETC) is integrated with the ECM, which uses data from multiple sources, including the transmission’s shift patterns and traction at the drive wheels, in determining how far to open the throttle. With this data, the V-6 effectively anticipates the driver’s demands, whether it’s a slow-speed parking maneuver or wide-open throttle operation on the open road, and responds appropriately. ETC delivers outstanding throttle response and greater reliability than a mechanical connection. Cruise control electronics are integrated in the throttle, reducing the amount of wiring required, further improving reliability and simplifying engine assembly.

The global V-6’s coil-on-plug ignition delivers the highest energy spark and most precise timing available. The increased efficiency of coil-on-plug spark contributes to lower emissions. The system has no high-tension spark plug wires and fewer parts than conventional ignitions, improving durability, allowing more efficient engine assembly and enhancing build quality.

Spark timing is managed with both a cam sensor that reads a reluctor wheel on the cam phaser and a sensor that reads a reluctor wheel pressed onto the crankshaft. This dual-measurement system ensures extremely accurate timing for the life of the engine. Moreover, it provides an effective back-up system in the event of a sensor failure.

On the global V-6, a single ME9 microprocessor manages the following functions and more: Cam phasing for variable valve timing, which improves performance and efficiency; electronic throttle control, with different throttle progressions based on operating conditions and driver demand; torque management for traction control and all-wheel drive; the returnless fuel injection system with injection and spark-timing adjustments for various grades of fuel; the ignition system and knock sensors, which push spark advance to the limit of detonation (hard engine knocking) without crossing over, maximizing fuel economy; fast-heating oxygen sensors with pulse-width modulation, which varies electrical current like a rheostat rather than an on-off switch and allows lower cold-start emissions; and the variable intake manifold. The ECM provides a limp-home mode for ignition timing, in the event either the crank or cam sensor fails. It will continue to control timing based on data from the functioning sensor, and advise the driver with a warning light. It also provides coolant loss protection, which allows the V-6 VVT to operate safely at reduced power, even after there has been a total loss of engine coolant, so the driver can reach a secure location. Additionally, the ECM allows a number of other customer-friendly features, including GM's industry-leading Oil Life System

The 2.8L V-6 Turbo also uses a torque-based control strategy, which improves upon previous throttle-based management systems that rely exclusively on the throttle position sensor to govern throttle operation for the ETC. The torque-based strategy calculates optimal throttle position, the position of the intake plenum plate, cam phasing positions and other operational parameters and translates that data into an ideal throttle position and engine output, based on the driver’s positioning of the gas pedal.

The global V-6 exhaust manifolds are double-wall steel and the cam covers are aluminum.