2.9L and 3.7L Vortec

[Derek77]

Larger-Displacement 2.9L and 3.7L Vortec Inline Engines Deliver More Power

PONTIAC, Mich. - For the 2007 model year, GM's popular midsize trucks - Chevrolet Colorado and GMC Canyon - as well as the HUMMER H3 SUV, feature new, larger-displacement inline four- and five-cylinder engines. The new Vortec 2.9L I-4 and Vortec 3.7L I-5 deliver more horsepower and torque than the engines they replace, giving the vehicles increased performance.

The Vortec 2.9L DOHC four-cylinder with variable valve timing (VVT) replaces the previous 2.8L four-cylinder and delivers 185 horsepower (138 kW) and 190 lb.-ft. of torque (258 Nm).* The Vortec 3.7L DOHC five-cylinder with VVT replaces the previous 3.5L engine and is rated at 242 horsepower (180 kW) and 242 lb.-ft. of torque (328 Nm).*

The 2.9L engine produces approximately 6 percent more horsepower and 3 percent more torque than the previous four-cylinder, while the 3.7L offers a substantial 22-horsepower increase and 17 lb.-ft. more torque than the previous five-cylinder engine. The 2.9L is standard in all 2007 Colorado and Canyon models except 4WD Crew Cab; the 3.7L engine is standard in 4WD Crew Cab models and available on all others. The 3.7L engine is the only engine offered on the '07 HUMMER H3 and H3X.

GM's inline engines meet the diverse demands of midsize pickup and SUV customers. The I-4 engine delivers more power than many other comparable four-cylinders, while the more powerful I-5 offers comparable power and torque to many competitors' six-cylinders.

Increased bore diameter

Both new engines are based on GM's modular inline engine design, which also serves as the foundation for the award-winning 4.2L I-6 in the Chevy TrailBlazer, GMC Envoy and Saab 9-7X. They feature dual overhead camshafts, variable valve timing, electronic throttle control and other features that contribute to high levels of operating efficiency and fuel economy. Balance shafts help ensure smooth operation and reduced vibration of the engines, providing a higher level of refinement.

In addition to their larger displacement - delivered through larger, 3.76-inch (95.5 mm) bores - the 2.9L and 3.7L engines feature improved airflow in and out of the combustion chambers, which helps boost power. They also share additional upgrades and changes, compared to the previous engines:

-Larger, 1.52-inch (38.7 mm) intake valves, vs. previous 1.45-inch (37 mm) intake valves

-Larger, 1.32-inch (33.5 mm) exhaust valves, vs. previous 1.18-inch (30 mm) exhaust valves

-Revised camshaft profile optimizes valve lift and duration in accordance with larger valves

-Cylinder head airflow increased to match capabilities enabled by larger valves and revised camshaft

-New, noise-reducing oiling system uses cylinder wall squirter system enabled by a hole in each connecting rod that delivers a precise oil stream onto the cylinder wall beneath the piston

-New aluminum camshaft cover helps reduce noise

-Tighter-clearance balance shaft bushings promote quieter operation

-New, 2-megabyte powertrain control module houses new diagnostic information storage

-New cartridge-type engine block heater, which fits neatly into a specially machined block orifice; for use with available engine block heater.

Additionally, the 3.7L five-cylinder engine has several features that help it meet new BIN 5 emissions requirements, including a larger, close-coupled catalytic converter and A.I.R. system.

VVT-enhanced performance

The new inline engines employ state-of-the-art air-fuel and spark management, including a dual-overhead cam valvetrain, four-valves-per-cylinder, variable valve timing and coil-on-plug ignition. Like the common-design engine blocks, the aluminum cylinder heads for the 2.9L and 3.7L are modified four- and five-cylinder versions of the 4.2L I-6 head. The cylinder head design includes chain-driven camshafts with large sprockets to ease the load carried by the timing chain. Also, a roller follower valvetrain reduces friction to improve engine performance and fuel economy, while reducing noise.

VVT enhances performance and improves emissions by regulating the timing of the opening and closing of the exhaust valves. With VVT, camshaft lobe profiles are selected to enhance power, torque and engine smoothness, and the valve timing is optimized for the camshaft at different rpm levels by the PCM. VVT also eliminates the need for external exhaust gas recirculation (EGR) and contributes to improved emissions. With VVT, the exhaust valves' timing can be adjusted to "retard" the exhaust cam, thereby creating internal EGR. These leftover gases are recycled into the next burn cycle, improving emissions and engine performance.

Coil-on-plug ignition delivers a high-energy spark, contributing to a cleaner, more consistent burn of the air-fuel mixture. The system uses a separate ignition coil for each cylinder, mounted above the spark plug. An electronic engine-sensing spark control system sends energy to the coils, eliminating the need for timing adjustments.

The engines also benefit from numerous quality-enhancing characteristics:

-Electronic throttle control allows the tailoring of throttle position to optimize driveability, fuel economy and emissions control

-Accessories - including a new, 125-amp alternator featuring Regulated Voltage Control - are mounted directly to the engine block to reduce vibrations

-The air intake plenum is constructed with sound-absorbing foam to reduce noise heard in the passenger compartment

-High-mounted starter is shielded from road splash

-GM Oil Life System permits oil-change intervals of 5,000-15,000 miles

The engines also feature an exhaust manifold-mounted, three-way catalytic converter design. Constructed as part of the manifold, the close-coupled converter provides optimum light off (quickly reaches high temperature) to oxidize, primarily, hydrocarbon and carbon monoxide emissions.

Shared traits

The inline engines share much of their design and technology, including dual-overhead cams, four valves per cylinder, variable valve timing (VVT), sequential fuel injection and a coil-on-plug ignition system. Approximately 75 percent of the I-4 and I-5 engines' components are shared with the larger Vortec 4.2L I-6, and about 90 percent of the four- and five-cylinder engines' parts are common. This permits increased assembly efficiency that affords GM greater flexibility in adjusting the production of each engine to meet consumer demand.

The foundations of the engines' design are deep skirt, cast aluminum engine blocks. They are produced with a lost foam process that allows more precise dimensional control, while reducing necessary finish machining in oil galleries, coolant passages and other internal passages. The deep-skirt design places block material below the crankshaft centerline to enhance rigidity of the block, while the lightweight aluminum offers better control of oil temperature, eliminating the need for auxiliary oil cooling. The lighter-weight engine block enhances fuel economy, too, by reducing overall mass.

In addition to superior dimensional accuracy and less need for finish machining, lost foam casting also allows the blocks to be produced with fewer pieces and more complex shapes. Overall, fewer pieces are needed to assemble the engines, and the accuracy of the casting process results in less scrap. And because the dry sand used in the casting process requires no bonding agent, it does not have to be discarded as solid waste. In fact, the sand is re-used for future castings.

At the assembly stage, the I-4 and I-5 engine blocks are fitted with balanced crankshafts and main bearing caps that are designed to add strength and reduce noise and vibration. Also, the engines' oil pans are structural members, contributing to overall stiffness. Both the four- and five-cylinder engines' crankshafts are specially counterweighted for their unique cylinder configuration.

The 2.9L and 3.7L engines are built at GM's Tonawanda, N.Y., engine assembly plant.

*Horsepower and torque certified. A new voluntary power and torque certification procedure developed by the SAE Engine Test Code committee was approved March 31, 2005. This procedure (J2723) ensures fair, accurate ratings for horsepower and torque by allowing manufacturers to certify their engines through third-party witness testing. GM was the first auto manufacturer to begin using the procedure and expects to use it for all newly rated engines in the future.

Edited June 19, 2006 by Derek77