GM Powertrain Debuts New Engines at SEMA

GM Powertrain is using the 2003 SEMA trade show in Las Vegas to show off three new engines, including two engines with Displacement on Demand (DOD) cylinder-deactivation technology for improved fuel economy. GM expects two million vehicles with DOD-equipped V-8 and V-6 engines will be on the road by 2008. GM Powertrain is also showcasing a new Ecotec 2.4 liter engine, which brings both larger displacement and variable valve timing to the Ecotec modular family.

For the new LE5 2.4 liter both cylinder bore and stroke are increased in relation to the original Ecotec 2.2 liter engine. The new engine's bore is 88 mm and stroke is 98 mm, versus the 2.2 liter's 86 mm bore and 94.6 mm stroke, yielding a total displacement of 2,384 cc versus the original 2.2 liter's 2,189 cc. Developed to enhance the low- and midrange torque output of the new engine, the new variable valve timing system uses electronically controlled hydraulic camshaft phasers to alter the relationship of the intake and exhaust camshafts as much as 50 degrees relative to the crankshaft.

"We have added technology to improve low-end torque and continue to reduce emissions. For the new Ecotec, variable valve timing helps deliver 90% of the torque peak at as low as 2400 rpm. That sort of responsiveness enormously enhances engine response."

Jay Subhedar, Ecotec global four-cylinder engine assistant chief engineer.

The Ecotec 2.4 liter, with 170 horsepower and 170 lb.-ft. of torque, will debut on the all-new 2005 Chevrolet Cobalt. The Cobalt will also be available with the latest version of the Ecotec 2.2 liter, expected to produce better than 140 hp at 5600 rpm and 150 lb-ft of torque at 4000 rpm.

The largest of GM's expanding family of 60° V-6 engines, the 3900 achieves larger displacement via an increase in bore size to 99 mm from the 3500 V-6’s 94 mm — requiring the bore centers to be ofset by 1.5 mm. Michalski said the 3900’s increased displacement fits glove-in-hand with Displacement on Demand: "A bigger engine is better when you want to maximize the amount of time the engine spends in three-cylinder operation," he explained.

The LZ8 3900 will be the first GM overhead valve engine to use variable valve timing, and it will be GM’s first V-6 to use DOD. The 3900's variable valve timing is coupled with another important new feature: a dual-path, active intake manifold.

"The variable intake manifold is a significant low-speed torque 'enhancer' for the 3900. It gives the 3900 a broader torque curve that retains higher specific torque output across the engine speed range."

Dick Michalski, chief engineer for 60-degree OHV V-6 engines.

The new 3900 V-6 (LZ8) is a 3.9 liter, two-valves-per-cylinder OHV V-6 that is most closely related to the 3500 V-6 (LX9) launched for the 2004 model year Chevrolet Malibu. Its first application without DOD will be on the 2005 Pontiac G6 in late 2004. A version of the 3900 V6 featuring the DOD system will debut in 2005.

The 3900 is estimated to develop 240 hp at 5900 rpm and 245 lb-ft of torque at just 2800 rpm. Moreover, thanks to the 3900's torque-enhancing technologies, 90% of peak torque is available from 1800 rpm to 5800 rpm, enhancing the engine's driveability and performance "feel." According to Alan Hayman, manager-advanced concept group in GM Powertrain's Advanced Powertrain unit, a new 3-valve cylinder-head developed for GM's OHV engines could boost output to 270 hp.

The Vortec 5300 small-block with DOD debuts on V-8-equipped versions of the 2005 Chevrolet TrailBlazer EXT, GMC Envoy XUV and Envoy XL. A version of the Vortec 5300 V-8 without DOD will be available in the 2005 Buick Rainier, while a larger version of the aluminum Gen IV engine block (again without DOD) will debut in the 2005 Corvette.

"The versatility, strength and performance of the legendary small-block V-8 continue to grow. In trucks we've maintained the broad, usable torque customers depend on for countless tasks, while in the Corvette, we've upped the ante with the largest, most powerful small-block ever offered as standard equipment. You'll have to wait until the 2004 North American International Auto Show to get the details, but believe me, it’s worth the wait."

Sam Winegarden, chief engineer of small-block engines.

The LH6 Vortec 5300 with DOD is rated at an estimated 290 hp and 325 lb-ft of torque in V-8 mode, and supports tow capacities comparable to the current LM4 5.3 liter aluminum small-block. GM is promising increased power from the small-block V8 in future, and not just from the new 3-valve cylinder heads.

"The 3-valve is a way in the future," Hayman told Wards Auto World. "There are some surprises in store for the 2-valve (small-block V-8). And we're not talking about 10 or 15 hp. Our goal is to remain the leader in truck powertrains."

A sophisticated, next-generation engine controller determines when to deactivate cylinders, allowing the engine to maintain vehicle speed in lighter-load conditions such as highway cruising. The process is seamless and virtually imperceptible. When the cylinders are deactivated the engine effectively operates as a V-4, with alternate cylinders on each cylinder bank disabled. The engine returns to V-8 mode the instant the controller determines the vehicle speed or load requires additional power.

Because the vibration and acoustic dynamics of the V-8 and V-4 modes are different, engineers tuned the exhaust system of DOD-equipped vehicles to compensate for the changes. A pressure-activated valve in the muffler automatically switches when the engine mode changes, adjusting the exhaust path to deliver the appropriate noise reduction. Additionally, tuned exhaust and engine mounts were designed for the multiphase engine operation. The engine's electronic throttle control (ETC) also is used to increase manifold pressure in V-4 mode so that the engine can maintain a V-8 torque load.