I ran out of popcorn and had some time on my hands so here are a couple of pics a video and technical specs for the 2013 Gen III 2.0 LTG Turbo and the Gen II 2.0 LNF Turbo. This application of the 2.0 LTG Turbo appears in the 2013 Cadillac ATS. I am sure Bogie will break down the differences for us in layman's terms:
GM 2.0 LTG Turbo:
DETROIT – A new, direct-injected Ecotec 2.0L turbocharged engine is available in the 2013 Chevrolet Malibu. It is rated at 259 horsepower (193 kW), making it one of the most power-dense automotive engines in the industry.
A twin-scroll turbocharger generates up to 20 pounds of boost, helping the engine optimize power delivery across the rpm band. It also produces a broad and robust torque curve, delivering 90 percent of the peak 260 lb.-ft. of torque (353 Nm) from 1,500 rpm to 5,800 rpm – giving the Malibu Turbo a great feeling of power on demand.
“With the twin-scroll turbo, there is basically no turbo lag and the feeling of power is instantaneous and satisfying,” said Mike Anderson, global chief engineer for Ecotec engines. “Better still, it is on-demand power, with the fuel efficiency of a small-displacement engine in most driving conditions.”
This added performance comes with greater refinement, as the enhanced torque reduces downshifts and helps quiet the buzz sometimes found in four-cylinder engines.
The 2.0T is based on the all-new Ecotec engine family – including the new 2.5L engine that also is new in the 2013 Malibu – and builds on the advanced-technology heritage of previous GM turbo engines with features that enhance efficiency, durability and refinement. Increased efficiency in all of the new Ecotec engines is achieved in part through lower engine friction, which was reduced by up to 16 percent using new technologies such as a variable-displacement oil pump.
GM proprietary computational fluid dynamics (CFD) analysis techniques were used to develop an all-new combustion system with a higher compression ratio, which also helped boost efficiency. Electronically controlled supporting components, including the wastegate and bypass, also help optimize performance and efficiency.
The new 2.0T engine features durability and technological features familiar in premium engines, including low-friction hydraulic roller-finger valve operation and an electronic throttle. A hydraulic tensioner keeps the timing chain adjusted for life, and extended-life spark plugs deliver 100,000 miles (160,000 km) of service. Additional engine features include:
A precision sand-cast engine block with cast-in-place iron liners
Forged steel crankshaft
Pistons with jet-spray cooling
Modular balance shaft system in the oil pan
Inverted-tooth chain drive systems
Rotocast aluminum cylinder head with sodium-filled exhaust valves
Dual Overhead Camshaft (DOHC) with continuously variable valve timing
Direct injection with cam-driven high-pressure fuel pump
Two-stage variable-displacement oil pump
Air-to-air intercooling system.
Engine block and rotating assembly: The sand-cast cylinder block provides excellent structural support and incorporates structural changes shared among the new Ecotec family that enable greater control of noise and vibration. Tough iron main bearing cap inserts are used on the block to locate the steel crankshaft with reduced noise and vibration. Refinements to the oil-distribution system enable improved oil flow throughout the engine, as well.
The forged steel crankshaft is strong and supports the high load of a turbocharged engine – while also contributing to high-rpm smoothness. It is complemented by strong connecting rods and aluminum pistons that are designed for the performance parameters of turbocharging. Piston jet-spray cooling reduces engine temperatures and friction by drenching the bottoms of the pistons with engine oil at higher engine speeds.
Greater engine smoothness comes from the modular balance shaft system, which is mounted in the oil pan. The design, which is part of the design changes with the new Ecotec family, minimizes the drive chain length and “buries” the system deep inside the engine to help reduce noise.
Inverted-tooth chain drives: The balance shaft and camshaft drive systems use a premium, inverted-tooth design that is significantly quieter than a roller-type chain. As its name implies, an inverted-tooth chain has teeth on its links – two-pin rolling pivot joints – that essentially wrap around the gear sprocket to take up virtually all the tension. This allows for smoother meshing of the chain links to the sprocket teeth, which is the cause of most noise in chain drive systems. The chain-to-sprocket tooth impact is greatly reduced with the inverted-tooth design (also known as a silent chain drive), which virtually eliminates noise and enhances durability.
Rotocast aluminum cylinder head with sodium-filled exhaust valves: The 2.0T’s A356T6 aluminum cylinder head is cast using a Rotocast process – similar to the heads on the supercharged Corvette ZR1’s engine – for high strength, reduced machining and improved port flow. The head is also designed specifically for direct injection, with unique injector mounting locations below the ports and port and combustion chamber designs optimized for direct injection and high boost pressure.
The head uses stainless steel intake valves that are nitrided for improved durability and undercut to improve flow and reduce weight. The exhaust valves have sodium-filled stems that promote valve cooling. At normal engine operating temperatures, the sodium inside the valve stem becomes liquid. The liquid sodium promotes heat transfer away from the valve face and helps maintain a lower, more uniform valve temperature. The result is reduced valve guide seat wear and consistent valve seating.
With performance the priority for this engine, the exhaust manifold is made of cast stainless steel to enable approximately 1,800-degree F (980 degrees C) turbine inlet temperatures with a dual-scroll manifold. It is extremely durable and delivers exceptional airflow.
DOHC with continuously variable valve timing: Continuously variable valve timing optimizes the engine’s turbocharging system by adjusting valve timing at lower rpm for improved turbo response and greater torque delivery.
Cam phasing changes the timing of valve operation as conditions such as engine load and speed 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.
Direct injection: Direct injection moves the point where fuel feeds into an engine closer to the point where it ignites, enabling greater combustion control. Because the ports are not used to mix the fuel and air, the airflow is increased, resulting in improved efficiency and power. The evaporation of the fuel in the cylinder cools the air-fuel mixture to a lower temperature than conventional port injection, which allows a compression ratio of 9.5:1. Direct injection also reduces emissions, particularly cold-start emissions, by about 25 percent.
Cam-driven high-pressure fuel pump: A high-pressure, camshaft-driven pump provides the fuel pressure required for the direct injection system. 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. Fuel pressure varies from about 750 psi at idle to 2,250 psi at wide-open throttle.
Two-stage variable-displacement oil pump: The variable-flow oiling system contributes to greater fuel efficiency, by matching the oil supply to the engine load. Rather than the speed-dependent output of a conventional, fixed-displacement pump, the engine’s variable-flow pump – which is driven off the balance-shaft module – changes its capacity based on the engine’s demand for oil. This prevents wasting energy to pump oil that is not required for proper engine operation.
Twin-scroll turbocharger and air-to-air intercooling system: The turbocharger system’s twin-scroll design is used to increase power. Each scroll on the turbine is fed by a separate exhaust passage – one from cylinders one and four, the other from cylinders two and three – to virtually eliminate turbo lag at low engine speeds.
Because direct injection cools the intake process compared to port injection, the 2.0T is designed with a relatively higher compression ratio of 9.5:1, compared with a conventional port-injected turbo engine. This enables higher boost for greater power and fuel efficiency.
An intake charge cooler enhances the power-increasing benefits of the turbocharging system. The air-to-air intercooler draws fresh air through a heat exchanger – much like a radiator – to reduce the temperature of compressed air that’s forced through the intake system by the turbocharger. Inlet temperature is reduced as much as 120 degrees C (250 F). Cooler air is denser, which means more oxygen is packed in the cylinders and available to burn fuel, consequently generating greater power.
GM 2.0 LNF Turbo:
IMPROVING AN ALREADY STURDY DESIGN
A lot of development work went into this new version of the Ecotec; it wasn't simply a matter of plunking a turbo on the engine. Indeed, every major casting was redesigned to provide a heightened level of reliability, though the engine was originally designed for use in forced-induction applications.
As with the new supercharged Northstar engine in the new Cadillac XLR, the displacement of the Solstice GXP's is slightly smaller than the normally aspirated version. Both feature a reduced bore size to increase cylinder-wall thickness. The Ecotec Turbo's stroke is also reduced and features a beefy, forged-steel crankshaft for additional durability. Bore and stroke are 86x86 mm (3.38x3.38 inches) for a total displacement of 1,998 cc's or 122 ci.
The Ecotec 2.0-liter Turbo uses a stronger "Gen II" Ecotec engine block, which was developed with input from racing experience to support increased horsepower and torque. Cylinder-block bulkheads -- the areas where the main bearing caps are attached -- and the cylinder walls are enlarged for strength. Other areas of the engine were enhanced to reinforce the structure, and the water jacket is deeper for added cooling capacity and improved cylinder-bore roundness. This architecture is shared with the 2.4-liter Ecotec engine that debuted in the Pontiac Solstice roadster.
Its bottom end is also upgraded to handle the additional boost. In addition to the forged-steel crankshaft, the Ecotec Turbo also employs forged connecting rods and cast pistons. The pistons feature a dish shape that deflects injected fuel toward the spark plugs. They are cooled with a jet-spray of oil on their undersides that directs the oil into a cast-in channel inside the piston, further resisting detonation.
Additionally, the Ecotec 2.0-liter Turbo four benefits from variable valve timing and an intercooled, twin-scroll turbocharger system to provide boost. A dual-scroll design is used on the exhaust turbine and speeds up velocity and response, much in the same way a two-plane intake manifold performs the identical function. The result is a nearly lag-free system, one that gives the 2.0-liter four the feel of a much larger engine. Dual cam phasing complements the turbocharging by optimizing valve timing at lower rpm for best turbo response and quick engine build-up time. "There is virtually no lag with this system," says Ed Groff, assistant chief engineer, Ecotec 2.0-liter Turbo engine. "Throttle response is immediate. The engine acts like it has a larger displacement engine."
Its turbocharger provides up to approximately 20 pounds of boost. It is matched to the engine's displacement and performance objectives, and is supported by the air-to-air intercooling system, which reduces inlet temperature pf the turbo-compressed air by approximately 212 degrees (100 degrees C), enhancing performance because cooler air is denser.
Perhaps the most innovative feature of the new turbocharged Solstice powerplant is the direct injection system. Essentially, the system locates the injector in the combustion chamber rather than in the intake manifold runner or intake port. This arrangement is similar in layout to a diesel powerplant, exposing the injector to the heat and pressure of the combustion event. Unlike a diesel, the Eccotec uses a conventional spark plug and otherwise operates as a normal four-cycle spark-ignition engine. The system is referred to as Spark Ignition Direct Injection (SIDI).
With fuel delivered directly to the combustion chamber to create a more complete burn of the air/fuel mixture, less fuel is required to produce the equivalent horsepower compared to a conventional port-injection system, particularly at normal cruising speeds. "Direct-injection technology works well with turbocharging and helps deliver a great balance of power and economy," says Groff. "The Ecotec 2.0-liter Turbo produces the power expected of a V-6, but in a smaller, more efficient pacckage -- and the driving response is simply terrific."
To accomodate the direct-injection system, the Ecotec 2.0-liter Turbo has a unique cylinder head and intake manifold. The cylinder head incorporates mounting locations for the fuel injectors -- which are typically mounted in the intake ports or intake manifold on port injection engines. A high-pressure fuel pump delivers fuel to a variable-pressure fuel rail. Fuel enters the combustion chamber through multihole fuel injectors. The fuel pump, fuel-rail pressure, fuel injection timing, and injection duration are controlled by the engine control module. In this way, fuel is metered and delivered in a finely atomized spray, which, during the intake stroke, is introduced into the chamber near the intake valves, in direct line of the spark plug. SIDI also permits a slightly higher compression ratio than if the fuel were delivered with conventional fuel injection and allows the mixture to be leaner at full power.
A high-pressure, returnless fuel system is employed for this application. It features a high-strength stainless steel fuel line that feeds a variable-pressure fuel rail. Direct injection requires higher fuel pressure than conventional fuel injected engines, and an engine-driven high-pressure fuel pump is used to supply up to 2,250 psi of pressure. This system regulates lower fuel pressure at idle -- approximately 752 psi and higher pressure at wide-open throttle. The cam-driven, high-pressure pump works in conjunction with a conventional fuel tank-mounted supply pump.
Apart from the mounting position of the fuel injectors, the cylinder head has conventional port and combustion designs, although both are optimized for direct injection and high boost pressures. Sodium-filled exhaust valves and stainless steel exhaust manifold are durable components designed to stand up to the high-performance capability of the engine.
A unique cylinder head, fuel system, pistons, intake manifold, and the dual-scroll turbocharger are the olny major ccomponents that differentiate the 2.0-liter Turbo from other members of the Ecotec engine family. Mobil 1 synthetic engine oil is added at the factory. Synthetic oil was selected for its friction-reducing capabilities and high-temperature performance.
DUAL CAM PHASING
The camshafts of the Ecotec 2.0-liter Turbo engine have phasers that support the continuously variable intake and exhaust valve timing. They also have cam position sensors, so that the engine control module can accurately control valve timing. The crankshaft and camshaft position sensors are digital. A new engine controller, specific to this powerplant, is used to sense and dictate its performance parameters.
Variable intake and exhaust timing works synergistically with both the gasoline direct injection and turbocharging systems. The variable engine timing enabled by cam phasing allows the combustion process to be optimized. Also, valve "overlap" at low rpm can be adjusted by the controller to increase the response of the turbocharger, providing a more immediate feeling of power.
ECOTEC ENGINE FAMILY
The Ecotec 2.0-liter Turbo is built on a global platform that was designed at the outset for a range of performance and combustion capabilities. Gen II blocks support the high-performance demands of the engines, but are merely a strengthened version of the original Ecotec architecture. The oil pump, for example, is the same as used in all other Ecotec engines. It was originally designed to support high-performance applications of future engines.
"This 2.0-liter Turbo is the pinnacle of Ecotec performance to date, with additional growth planned," says Groff. The groundwork for its capabilities was laid on the drawing table at the beginning of the Ecotec's development. Prior work and a far-thinking engine design continue to help GM respond to market demands around the globe more quickly and with greater accuracy."
This new Ecotec family member also features:
Dual overhead camshafts (DOHC) and four valves per cylinder
Twin counter-rotating balance shafts for operational smoothness
"Drive by Wire" electronic throttle control
Low friction, roller-finger follower valvetrain with hydraulic lash adjusters
Low-maintenance chain-drive for the camshafts
58X camshaft positioning
Direct-mount accessories, which reduce or eliminate traditional sources of noise and vibration
Full-circle transmission to reduce noise and vibration
GM Oil Life System, which can reduce the frequency for oil changes
Innovative cast-in oil filter housing, which eliminates the need to crawl under the vehicle to perform oil changes and eliminates throwaway oil filter cans that retain used oil.
As with other engines in the Ecotec family, the 2.0-liter Turbo engine also has premium features designed to ensure smooth and quiet operation, including a polymer coating and skirt design for the pistons that reduce noise during cold starts. An automatic hydraulic tensioner also is used to maintain optimal tension on the timing chain, which reduces noise and vibration.
The Solstice GXP is expected to debut in the summer of 2006. If it does come with an MSRP in the $25,000 range, it will be a serious "bang for the buck" value, and we expect that once the hurdles of figuring out the electronics are overcome, the aftermarket will quickly gear up with a host of performance upgrades. We see no reason to think this engine would have any problem supporting over 500 streetable horsepower, which would make for an insanely fast machine that would also get great mileage -- if, of course, you could keep your foot out of it.
We have been given ample evidence that GM and Pontiac-GMC have come a long way to understanding how to market an affordable two-seat performance car. It appears the bitter lessons learned by the demise of the Fiero have not been lost. With an attractively priced performance package that should deliver on all fronts, a realistic sales forecast, innovative marketing, and the potential for even more power, the Solstice GXP could end up being one of the best performance cars Pontiac has ever released. It had better be -- Pontiac and GM really cannot afford anything other than a grand slam.