|The 2010 Terrain will feature a choice of two new direct injection engines. Click to enlarge.|
The newly introduced GMC Terrain (earlier post) became the latest GM North American model that will feature a fuel-efficient gasoline direct injection (DI) engine in 2010. For MY 2009, GM is offering 6 engine variants with direct injection in 10 models in North America, 18 worldwide. For the 2010 MY, GM will have eight direct-injected engines in 38 vehicle models worldwide, with 18 models in North America alone.
The MY 2009 engines include three 2.0-liter Ecotec variants (LNF, LHU and LDK); a 2.2L Ecotec (LCH); and two 3.6-liter variants (LLT and LCS). These are joined in 2010 by the new Ecotec 2.4L (LAF) and 3.0L V-6 (LF1) direct injection engines.
|The new MY 2010 2.4L I-4 VVT DI Ecotec (LAF). Click to enlarge.|
2010 Ecotec 2.4L I-4, VVT DI (LAF). The new Chevrolet Equinox and GMC Terrain vehicles will offer the Ecotec 2.4L I-4 VVT DI Engine (LAF) for the 2010 model year. This Ecotec engine is installed transversely, and equipped with either a Hydra-Matic 6T45 FWD or AWD six-speed automatic transmission. The 2.4L direct injection engine generates 182 hp (136 kW) of power and 172 lb-ft (233 N·m) of torque.
The direct-injection fuel injectors inject fuel directly into the combustion chamber and are located beneath the intake ports, which transfer only air. Because the ports are not used to mix the fuel and air, efficiency of the air flow is increased. In addition, the control of the injection event, via direct-injection technology, is very precise and results in better combustion efficiency and fuel consumption at all throttle openings.
A higher compression ratio (11.4:1 in the LAF engine) is also possible due to a cooling effect as the injected fuel vaporizes in the combustion chamber. This cooling effect reduces the charge temperature reducing the likelihood of spark knock. The direct-injection fuel injectors have been developed to withstand the greater heat and pressure inside the combustion chamber, and also utilize multiple outlets for best injection control.
The increased combustion efficiency and control helps to reduce emissions, particularly during cold starts, which is when the bulk of emissions are created.
The direct-injection system allows a more complete burn of the fuel in the air-fuel mixture, and it operates at lower temperature than port injection. That allows the mixture to be leaner (less fuel, more air). Less fuel is required to generate a given amount of horsepower, particularly at part-throttle operation. An engine with direct injection can deliver comparable power to a much larger displacement port-injected engine, with significant fuel savings.
|GM North America Gasoline Direct Injection Applications|
|MY 2009||MY 2010|
(announced to date)
|Saturn Sky Red Line
Pontiac Solstice GXP
Chevrolet HHR SS
|Saturn Sky Red Line |
Pontiac Solstice GXP
Chevrolet HHR SS
Cadillac Sports Wagon
A high-pressure, cam-driven pump provides the fuel pressure required for the direct injection system. The high-pressure pump is mounted on the end of the cylinder head and is driven by the intake cam. The engine mounted fuel pump is augmented by a conventional electrically operated supply pump in the fuel tank. The fuel delivery system features a high-pressure stainless steel feed line and a pressure-regulated fuel rail, without a conventional fuel return line from the engine to the tank.
The engine management system uses a sophisticated controller (ECM) designed to drive the high pressure fuel system and provide software and calibration capability to control all of the engine’s hardware and engine management systems.
The Ecotec 2.4L has a 319 aluminum cylinder head cast with advanced semi-permanent mold technology. This provides excellent strength, reduced machining, and improved port flow. No heat treatment to the casting also reduces residual stress, thus providing increased durability. The cylinder head is designed specifically for direct injection, where the fuel is injected into each combustion chamber.
This is accomplished by positioning an injector under the intake port of each cylinder, such that they protrude into the chamber. In contrast, the previous 2.4L Ecotec engine had the fuel injectors mounted to inject fuel into the intake ports. The combustion chamber and ports are optimized for direct injection, and high port flow. This design supports improved performance, emissions and fuel economy over the previous combustion system.
The cylinder head includes premium valve seat, valve guide, and valve materials. They were selected for minimum wear while operating in more severe conditions associated with direct injection and alternate flex fuels, such as ethanol E85. These premium materials along with a hydraulic lash adjusting lifter assure good durability without required lash adjustments during the engine life cycle. Direct injection and flex fuels require a more robust valvetrain system due to the increased friction, higher thermal loads, increased oxidation and reduced lubrication associated with alternate fuels that do not contain some of the natural lubricants found in gasoline.
The cylinder head has integral cast oil passages that feed a set of internal oil control valves that activate cam phasers, enabling variable valve timing.
Continuously variable valve timing (VVT) optimizes the engine. Both the intake and exhaust cams have hydraulically operated vane-type phasers that are managed by a solenoid and directed by the engine control module (ECM). The phasers turn the camshaft relative to the drive sprocket, allowing intake and exhaust valve timing to be adjusted independently.
|Cam phasers and cam shafts for the LAF engine. Click to enlarge.|
Cam phasing changes the timing of valve operation as conditions such as rpm and engine load vary. It allows an outstanding balance of smooth torque delivery over a broad rpm range, high specific output and good specific fuel consumption. Cam phasing also provides another effective tool for controlling exhaust emissions. Because it manages valve overlap at optimum levels, it eliminates the need for a separate exhaust gas recirculation (EGR) system. Variable valve timing can be even more valuable in turbocharged engine. The ECM can adjust valve overlap at low rpm to optimize turbo response, delivering a more immediate rush of acceleration-producing torque.
The cams feature 4X timing reluctors with digital sensors. This state-of-the-art control system allows the ECM to accurately measure and adjust valve timing, with consistent performance over the engine’s anticipated useful life. The cam reluctors work in conjunction with a 58X crankshaft position encoder to ensure the precisely accurate spark timing required of a direct-injection engine. This dual timing system also provides a reliable back up in the event either a cam or crank sensor fails.
The Ecotec LAF sand cast cylinder block is a superior refinement of the 2.4L VVT (LE5) cylinder block which was first launched in 2006. The block was developed using the latest math-based tools for product design as well as for manufacturability.
From a design perspective, the main bearing bulkheads, which support the crank bearings, as well as the cylinder bore walls, have been significantly strengthened to support increased engine loads with only a minimal weight increase (approximately 2.2 pounds). Additionally, refinements to the oil distribution system enable improved oil flow throughout the LAF engine.
As the block casting is nearly common from a dimensional standpoint with previous Ecotec block variants, it provides improved structural support for the Ecotec LAF powerplant while continuing to be nearly transparent in machining and assembly operations.
All together, this means the block has been increased in strength to accommodate the additional power provided by SIDI while providing additional benefits in the areas of manufacturability and control of noise, vibration and harshness.
|Piston head and oil cooling jet. Click to enlarge.|
The LAF pistons use a lightweight design, resulting in less reciprocating mass inside the engine, increasing efficiency, decreasing vibration and enhancing the feeling of performance as the engine builds revs.
Each piston has its own directed jet that sprays oil toward its skirt, coating its underside and the cylinder wall with an additional layer of lubricant. The extra lubrication cools the pistons, reducing both friction and operational noise and helping ensure durability to match the engine’s high output.
|The new GM 3.0L V-6 VVT (LF1). Click to enlarge.|
2010 GM 3.0L V-6 VVT (LF1) . The new 3.0-liter DI engine delivers power, depending upon application, from 255-264 hp (190-197 kW), with torque of 217-222 lb-ft (294-301 N·m). With a compression ratio of 11.7:1 this engine achieves SAE-rated specific output of 88.5 hp/liter in the new Cadillac SRX.
The V-6 VVT’s engine block and cylinder heads are cast from A319 aluminum alloy. This aluminum-intensive construction means less weight and greater efficiency than conventional cast-iron engines, and less weight translates to improved vehicle fuel economy. The sand-mold-cast block features strong cast-in iron bore liners, six-bolt main caps, and inter-bay breather vents.
Four-valves-per-cylinder inverted tooth chain cam drive contributes to the smoothness and high output of both V-6 engines. Overhead cams are the most direct, efficient means of operating the valves, while four valves per cylinder increase airflow in and out of the engine.
A chain that is powered by the engine’s crankshaft drives the dual overhead camshafts over each bank of cylinders. The inverted tooth chain uses a 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. As a result, the noise created by the initial sprocket/chain impact is significantly reduced. The benefit to customers is much quieter and smoother sprocket-to-chain engagement, which enables a smoother and quieter engine.
|Intake manifold assembly. Click to enlarge.|
The upper intake manifold for the 3.0L V-6 is made from composite material and provides mass savings over an aluminum manifold yet the structure is designed to make it quiet.
The V-6 VVT’s nerve network is a new torque-based engine management system, which improves upon previous throttle-based management systems that rely exclusively on the throttle position sensor to govern throttle operation for the electronic throttle control (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.
A single microprocessor manages the following functions:
Cam phasing, which improves performance and efficiency and allows maximum valve overlap at appropriate times, in turn allowing sufficient exhaust gas recirculation without a separate EGR.
Electronic throttle control, with different throttle progressions based on operating conditions and driver demand.
Torque management for traction control.
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.
A limp-home mode for ignition timing. In the event either the crank or cam sensor fails, the ECM 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.
Other customer-friendly features, including GM’s Oil Life System.
The 3.0-liter engine uses the new E39 controller, with 32-bit processing power and 2 megabytes of Burst Flash memory, 128 kilobytes of external RAM and 3 megabytes of internal SRAM.
The 3.0L engine utilizes an integrated exhaust manifold, eliminating the need for separate exhaust manifold. The benefits include reducing the mass of the engine for improved fuel economy and faster catalytic converter light off, resulting in reduced emissions.
The 3.0L LF1 VVT engine employs positive crankcase ventilation, and even the PCV valve has been developed to virtually eliminate operational noise. The evaporative emission system performs to a leak-detection standard of .020 inch (about the size of a pin prick).
The V-6 VVT’s cam covers are made of thermoset, glass-filled polyester composite, a material that weighs less than the cast aluminum used on most premium engines and more effectively dampens noise. Required baffles are incorporated into the cover, which is manufactured as an assembly with seals and fasteners attached. In addition, surfaces on the cam covers were shaped to limit the broadcasting of undesirable noise, and the covers use isolating perimeter gaskets, as well as isolating radial lips around the tubes that accommodate the spark plugs. These effectively de-couple the covers from vibration generated in the block and engine during combustion. Acoustic dampening cam covers also have been added for additional NVH improvements.
The 3.0L LF1 VVT engines will be produced in St. Catharines, Ontario, Canada and Ramos Arizpe, Mexico.