NEW YORK – General Motors introduced its new and most powerful Ecotec 2.0-liter direct injection turbo engine in the 2007 Saturn Sky Red Line at the New York International Auto Show. It produces 260 horsepower (194 kw) and 260 lb.-ft. of torque (353 Nm),* making it GM’s highest specific output engine ever, at 2.1 horsepower per cubic inch of displacement (130 hp / 97 kw per liter).
The Saturn Sky Red Line and the Pontiac Solstice GXP are GM’s first spark ignition direct injection offerings for North America. Gasoline direct injection technology helps the Ecotec engine produce more power while maintaining the lower fuel consumption of a small displacement port-injected engine.
Variable valve timing and an intercooled, twin-scroll turbocharging system are used to optimize the Ecotec 2.0-liter Turbo engine’s performance.
“This new engine builds on our racing experience and outstanding reputation with the Ecotec family. It combines advanced engine technologies that deliver super-car performance,” said Tom Stephens, group vice president, GM Powertrain.
The Ecotec 2.0-liter Turbo was developed with the global resources of GM Powertrain in the United States and Europe, drawing on expertise from the naturally aspirated Ecotec 2.2-liter direct injection engine used in some European applications and the 2.0-liter turbocharged engines already in production.
With direct injection, fuel is 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, especially at normal cruising speeds, of a conventional port-injection combustion system.
“Direct injection technology works well with turbocharging and helps deliver a great balance of power and economy,” said Ed Groff, assistant chief engineer, Ecotec 2.0-liter Turbo engine. “The Ecotec 2.0-liter Turbo produces the power expected of a V-6, but in a smaller, more efficient package – and the driving response is simply terrific.”
A dual-scroll turbocharger with a lightweight turbine provides nearly instant power, and an air-to-air intercooling system bolsters the turbo’s performance by reducing inlet temperatures. Dual cam phasing complements the turbocharging system by optimizing valve timing at lower rpm for best turbo response and quick engine torque build-up time.
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. The cylinder block bulkheads – the areas where the main bearing caps are attached – and the bore 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.
Highlights of the Ecotec 2.0-liter Turbo engine include:
* Steel crankshaft
* Forged connecting rods
* Cast aluminum oil-galley pistons
* Jet-spray piston cooling
* 9.2:1 compression ratio
* Aluminum cylinder head with sodium-filled exhaust valves
* High-pressure engine-driven fuel pump
* Variable pressure fuel rail
* Dual-scroll turbocharger
Components including the steel crankshaft, forged connecting rods and cast aluminum pistons are high-strength items that enhance durability. Jet-spray oil cooling directed toward an oil-galley piston help reduce piston temperatures. The system delivers pressurized oil to continuously lubricate and cool the pistons, which reduces friction and noise and ensures durability for the engine’s higher power levels. To enhance combustion, the piston tops feature a dish shape that deflects injected fuel toward the spark plugs.
To accommodate 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 precision multi-hole 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.
Apart from the mounting positions of the fuel injectors, the cylinder head has conventional port and combustion chamber designs, although both are optimized for direct injection and high boost pressures. The sodium-filled exhaust valves and stainless steel exhaust manifold are durable components designed to stand up to the high-performance capability of the engine.
The unique cylinder head, fuel system, pistons, intake manifold and the dual-scroll turbocharger are the only major components that differentiate the 2.0-liter Turbo from other members of the Ecotec engine family. Mobil 1 synthetic engine oil is installed at the factory. Synthetic oil was selected for its friction-reducing capabilities and high-temperature performance.
How direct injection works
Gasoline direct injection differs from the fuel delivery process of a conventional engine by delivering fuel directly into the combustion chamber, where it is mixed with air drawn into the chamber. The combustion process of conventional fuel-injected engines uses air and fuel that are mixed in the intake port or intake manifold prior to being introduced into the combustion chamber. Direct injection is a continuation of the evolutionary process of moving the fuel introduction point closer to the combustion location to improve control.
With the Ecotec 2.0-liter Turbo, fuel is introduced directly to the combustion chamber during the intake stroke. As the piston approaches top-dead center, the spark plug ignites the mixture, giving the name spark ignition direct injection (SIDI). The fuel injectors are located beneath the intake ports. SIDI allows the mixture to be “leaner” – less fuel, more air – at full power. SIDI also permits a slightly higher compression ratio than if the fuel were delivered with conventional fuel injection. The result is better fuel consumption at part and full throttle. The engine uses conventional spark plugs similar to those in other Ecotec engines.
A high-pressure, returnless fuel system is employed. 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 (155 bar) of pressure. The system regulates lower fuel pressure at idle – approximately 752 psi (50 bar) and higher pressure at wide-open throttle. The cam-driven high-pressure pumps works in conjunction with a conventional fuel tank-mounted supply pump.
Direct injection’s precise fuel delivery enables more complete combustion to help reduce emissions, particularly on cold starts – the time when most engine emissions are typically created. Also, direct injection permits a higher compression ratio in the engine, which positively influences fuel economy. At certain power levels, the boosted SIDI engine can provide significant fuel economy benefits compared to a larger displacement naturally aspirated engine.
A unique, dual-scroll turbocharger is partnered with an air-to-air intercooling system to provide up to approximately 20 psi (1.38 bar) of power-enhancing boost. The dual-scroll turbocharger delivers nearly instant response, as dual exhaust passages from the engine to the turbine housing guide exhaust gas to the turbine. This reduces lag time, or spool-up, at low rpm.
“There is virtually no lag with this system,” said Groff. “Throttle response is immediate. The engine acts like a larger displacement engine.”
The turbocharger is matched to the engine’s displacement and performance objectives. It is supported by the air-to-air intercooling system, which uses fresh air drawn through a heat exchanger to reduce the temperature of the warmer compressed air forced through the intake system by the turbocharger. Inlet temperature is reduced by approximately 212 degrees Fahrenheit (100 degrees C), enhancing performance because cooler air is denser and promotes optimal combustion.
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 the engine, is used to sense and control the engine’s 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 family traits
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. The Gen II block supports the high-performance demands of the engine, but it is merely a strengthened version of the original Ecotec architecture. The oil pump, for example, is the same as those used in all other Ecotec engines. It was originally designed to support high-performance applications of future engines.
“The 2.0-liter Turbo is the pinnacle of Ecotec performance to date, with additional growth planned. The groundwork for its capabilities was laid on the drawing table at the very beginning of the Ecotec’s development,” said Groff. “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 has traits that have helped forge a reputation for durability and sophistication:
* Dual overhead camshafts (DOHC) and four valves per cylinder
* Twin counter-rotating balance shafts for operational smoothness
* Electronic throttle control
* Low-friction, roller-finger follower valvetrain with hydraulic lash adjusters
* Low-maintenance chain-drive for the camshafts
* 58X crankshaft positioning
* Direct-mount accessories, which reduce or eliminate traditional sources of noise and vibration
* Full-circle transmission mount to reduce noise and vibration
* GM Oil Life System, which can reduce the frequency of 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 reduces noise during cold starts. An automatic hydraulic tensioner also is used to maintain optimal tension on the timing chain, which reduces noise and vibration.