Power launch: three new GM powertrains offer more power and showcase Displacement on Demand and variable valve timing technologies

Automotive Industries, Dec, 2003 by John Peter

At a recent GM Powertain event, Tom Stephens, group vice president, powertrain, laid out GM's new advanced propulsion plan for the near, mid and long term.

According to Stephens, the goal of GM's technology strategy is to reduce vehicle emissions. "If you want to have zero emissions and a huge increase in furl economy there's really only one answer that we're aware of. And that lies in the hydrogen economy and the hydrogen furl cell powered vehicle," Stephens says.

But while GM's ultimate goal is still to bring one million furl cell powered vehicles to commercial market by 2010, Stephens realizes that GM needs to take integral steps on its "March to Zero" as the plan is known internally.

"It's not enough though just to have a long term strategy," Stephens says, "you need to have a near term and a mid-term strategy and we have those as well."

GM's near-term powertrain strategy is focused on improvements to its internal combustion engines, developing technologies that will enhance the furl economy of the soft and full hybrids that make up the mid-term strategy.

"We're after higher levels of fuel economy, power and torque, all at the same time," says Stephens.

Stephens says that GM is looking for 60 hp per liter for naturally-aspirated engines and about 100 hp per liter for turbocharged engines. Engineers are also developing spark ignition direct injection for global applications.

Cam phasers are high on GM's list of powertrain technologies. Stephens says that by 2007, 2.5 million GM powerplants will be equipped with variable valve timing (VVT).

"In addition," says Stephens, "we're looking at variable induction tuning on our overhead valve engines."

According to Stephens, displacement on demand, a furl-saving technology that allows six and eight-cylinder engines to run on half of their cylinders in certain conditions, will be installed on two million engines annually by 2008.

In addition, the DOHC four-valve engines benefit from two-step valve trains plus port deactivation which Hill find its way onto one million engines by 2006.

On the emissions side, Stephens offers that all future advanced control system algorithms will be model based. "So we can do them fast and right the first time."

Work continues on the combustion system. Catalytic converters are being mounted closer to the engines to improve their performance and exhaust manifolds are being integrated into cylinder heads. There is also an emphasis on active intake manifolds and Stephens says, in some cases, engineers will look at integrating turbochargers into exhaust manifolds.

Consumers will get to test a few of GM's near-term ICE strategies on three new powerplants that Hill be brought to market the end of this year and early next year.

GM's first production applications of Displacement on Demand (DOD) will find its way onto the fourth generation Vortec 5300 small block V-8, standard on the 2005 Chevrolet Trailblazer EXT, GMC Envoy XL and Envoy XUV, as well as a DOD-equipped Vortec 3900 V-6, which will debut in the Pontiac G6, the Grand Am replacement due this spring. A version of the 5300, sans DOD is available now in the Buick Ranier and a non-DOD automotive application of the 5300 will debut later this year in the '05 Corvette.

The brains behind DOD is the E40 engine controller. The controller monitors such things as oil temperature, rpm, coolant temperatures and throttle position and determines when to drop cylinders and vice versa.

The seamless shifts occur through the activation of two-stage hydraulic valve lifters. In normal mode, the inner and outer lifter sleeves are held together by a pro. DOD is activated by delivering high pressure off to the lifters, which depress the pin and allow the outer portion of the shaft to move with the cam lobe while the inner portion doesn't move, holding the pushrod in place. The electronic operation is achieved through the lifter oil manifold assembly (LOMA), mounted in the engine valley. The LOMA is equipped with solenoids that trigger the switching lifters.

Oil circulation and pushrod length are the same for all cylinders while camshaft lobes are customized for the deactivated cylinders.

Because of the change in acoustic dynamics and vibration with the switch from four to eight cylinder mode, engineers added a pressure-activated valve in the muffler that automatically switches with the engine, adjusting the exhaust path to deliver the appropriate noise reduction.

DOD-equipped engines also have specially-tuned exhaust and engine mounts.

The engine's electronic throttle control is designed to increase manifold pressure in DOD mode to maintain engine torque.

Vortec 5300

The Gen IV Vortec 5300 shares the deep skirt engine block design of the previous GM truck engine, allowing for cross-bolted main bearings for added strength. The all-aluminum truck engine is rated at an estimated 290 hp and 325 lb.-ft, of torque in V-8 mode with no changes in towing capabilities.

The new block casting has redesigned oil galleries to meet the oiling requirements needed for DOD. The knock sensors and camshaft sensor have been moved to provide room for the new oil galleries. A higher capacity oil pump and larger coils on the coil-near-plug ignition are also need for DOD. All models now feature electronic throttle control for improved throttle response and DOD signaling. The transmission now has its own controller due to the demands that DOD puts on the ECM.