New GM EcoTec3 engine family for 2014 Silverado and Sierra pickups; direct injection, cylinder deactivation and CVVT
|2014 4.3L V-6 EcoTec3 AFM VVT DI (LV3) for Chevrolet Silverado and GMC Sierra. Click to enlarge.|
The newly unveiled 2014 Chevrolet Silverado 1500 and GMC Sierra 1500 pickup trucks will deliver more power, more torque and improved fuel efficiency, partly due to a trio of all-new EcoTec3 engines designed specifically for the needs of full-size truck customers. (From January through November 2013, GM has sold 506,088 Silverados and Sierras—22% of all vehicles it sold in that period.)
EcoTec3 engines feature three advanced technologies—direct injection, cylinder deactivation and continuously variable valve timing (CVVT)—to make the most of power, torque and efficiency across a broad range of operating conditions. The new engine family includes a 4.3L V6, a 5.3L V-8 and a 6.2L V-8, all matched with six-speed transmissions.
SAE-certified horsepower and torque ratings and EPA fuel economy estimates for the new Silverado and Sierra will be available beginning early next year.
Although the EcoTec3 engines for the 2014 Silverado and Sierra are all new—sharing just a handful of small parts with previous engines—they build on a foundation of more than 100 million Small Block engines and billions of real-world customer miles.
At the core of the new EcoTec3 engine family is an advanced combustion system that maximizes the potential of the direct fuel injection system, cylinder deactivation, continuously variable valve timing and other technologies.
More than 100 iterations of the combustion systems were evaluated through computer modeling before a final design was selected for each engine variant. The overall engine design involved more than 10 million hours of computational CPU time, with the combustion process alone accounting for more than 6 million of those CPU hours.
The ability to more precisely control combustion also enables the new engines to run with a higher compression ratio—11.0:1 for the versions with regular fuel recommended. This higher compression is one of the best ways to simultaneously increase both power and efficiency, GM noted.
This increased efficiency can be maintained over a broader range of operating conditions. For example, when towing a trailer on a hot summer day, Silverado and Sierra’s combustion system can reduce the need to trim back spark advance to control detonation, helping maintain both performance and real-world fuel efficiency.
Emissions are also reduced, particularly during cold starts, with hydrocarbon emissions cut by about 25%.
DI and combustion. The EcoTec3 engines use direct fuel injection, which precisely meters fuel directly into the cylinders, to optimize combustion over a broad range of conditions. The engines also feature a new cylinder-head design and a new, sculpted piston to optimize the mixing of air and fuel in the engine and the burning of the mixture to create power.
The heads features smaller combustion chambers shaped to complement the unique topography of the piston heads. The smaller chamber size and sculpted pistons produce a compression ratio of 11.0:1 or higher, depending on the engine, while the heads features large, rectangular intake ports with a slight twist to enhance mixture motion.
To further enhance combustion, the intake and exhaust valve positions have been switched from previous versions, and the valves are now slightly canted toward the cylinder centerline. Also, the spark plug angle has been revised and the electrode is now closer to the center of the chamber to support optimal combustion.
The pistons feature unique sculpted topography that was optimized via extensive computer analysis to precisely direct the fuel spray for better mixing and more complete combustion. The contours of the piston heads are machined after casting to ensure dimensional accuracy—essential for precise control of mixture motion and the compression ratio.
“GM pioneered cylinder deactivation technology, and we consider it a great technology for improving the efficiency of full-size trucks.”|
—Jordan Lee, Small Block chief engineer and program manager
Cylinder deactivation. Cylinder deactivation, also known as Active Fuel Management, is now standard on all three engines for the Silverado and Sierra 1500.
The new trucks maximize the use of cylinder deactivation with improved engine mounts, electronic throttle control, adaptive exhaust systems, improved aerodynamics, low-rolling resistance tires, and other technologies that help the engines operate in four-cylinder mode for longer periods of time, further increasing efficiency.
The system uses oil pressure, controlled by the powertrain control module, to deactivate the lifters on selected cylinders, closing the valves for those cylinders. It deactivates four of the cylinders on the V-8 engines and two cylinders on the V-6 under light load conditions—operating the engines as a V-4—and seamlessly reactivates the cylinders when the driver demands greater power. The transition takes less than 20 milliseconds and is virtually imperceptible.
Architecture. Engines based on the Small Block architecture are typically smaller and lighter than competitive engines with overhead camshafts, and typically have lower friction. Although package size is usually not a concern with full-size pickups, lighter weight and lower friction can both contribute to improved efficiency.
For 2014, all three engines for the Silverado and Sierra use lightweight aluminum blocks with cast-in iron cylinder liners. The blocks were developed with math-based tools and data acquired in GM’s racing programs, providing a light, rigid foundation for a smooth and strong engine.
The deep-skirt block design helps maximize strength and minimize vibration. Cross-bolted main bearing caps are secured to the block with four main bolts and two cross bolts each. A structural aluminum oil pan further stiffens the bottom of the block. The result is an engine that is quieter, smoother and more dependable, even under the toughest conditions.
Advanced oiling system. The oiling system incorporates a new variable-displacement oil pump that enables more efficient oil delivery, based the engine’s operating conditions. Its dual-pressure control enables operation at a very efficient oil pressure at lower rpm, and then delivers higher pressure at higher engine speeds to provide a more robust lubrication.
Oil capacity has been increased to six quarts for the 4.3L V-6 and eight quarts for the V-8 engines. All engines use GM’s Dexos oil for increased fuel efficiency and longer oil life, and V-8s are engineered to use 0W/20 oil to improve lubrication and reduce friction.
All trucks also feature GM’s oil life monitor, which better protects engines by recommending oil changes based on actual engine operating conditions and can save owners’ money by avoiding unnecessary oil changes.
Oil-jet piston cooling. At higher engine speeds, small jets spray oil on the underside of each piston. This helps reduce piston temperature, enabling the engine to maintain maximum horsepower and torque, and also reduces engine noise.
PCV-integrated rocker covers. New domed rocker covers house a patent-pending integrated positive crankcase ventilation system that enhances oil life, reduces oil consumption and reduces exhaust emissions. The domed sections of the covers contain baffles that separate oil and air from the crankcase gases, with about three times the oil/air separation capability of previous engines.
Exhaust manifolds. The exhaust manifolds were developed to improve durability and sealing and reduce operating noise. The cast iron manifolds feature saw cuts along their cylinder head mounting flange, which split the flange into three separate sections on the V-6 and four separate sections on the V-8s, allowing each section to move under extreme hot-cold temperature fluctuations to virtually eliminate movement of the exhaust manifold gaskets.
That helps ensure proper sealing for the life of the engine and reduces the chance of gasket failure. The exhaust manifolds also feature triple-layer stainless steel heat shields, which limit heat transfer to the engine bay and help further reduce noise.
Other features. Additional features and technologies of new Silverado and Sierra engines include:
A revised cooling system with an offset water pump and thermostat for more efficient performance;
An air induction humidity sensor ensures optimal combustion efficiency, regardless of the surrounding air’s humidity;
All engines feature an engine-driven mechanical vacuum pump to enhance braking performance;
58X ignition system with individual ignition coil modules and iridium-tip spark plugs; and
All-new “E92” engine controller.