February 11, 2013
Ecotec 3 6.2L V8. Click image to enlarge
Article by Justin Pritchard, photos courtesy GM
Chevrolet Silverado and GMC Sierra Ecotec 3 Engine Lineup
To the elation of GMC and Chevrolet truck and 4×4 enthusiasts across the internet, the new breed of GM trucks and utility vehicles is readying for a sales launch later this year.
Tony DiSalle, vice president of GMC Marketing, says “these trucks have all the power and capability that’s expected in today’s market, excellent fuel efficiency, plus a lot of unexpected, purposeful features developed with truck owners in mind.”
The new GMC Sierra, Chevrolet Silverado, and associated SUV variants (Tahoe/Yukon/Suburban) will soon hit dealers in a variety of models and trim levels that pack new features, new styling, new safety implements and new technologies.
They’ll also pack an all-new engine lineup, which consists of a 5.3L V8, a 6.2L V8 and a 4.3L V6. Displacements are the same as the last generation trucks, but GM officials say the engines only share a ‘handful’ of parts with the outgoing power units.
Dubbed ‘Ecotec 3’, the new family of GM truck engines promises plenty of durability, as well as some of the latest fuel-saving technologies included as standard.
Here’s a closer look at how GM says the Ecotec 3 powerplant range works hard to extract more clicks from every litre.
Ecotec 3 5.3L V8. Click image to enlarge. Click image to enlarge
Active Fuel Management: When full performance isn’t required, the Ecotec 3 engines can turn off cylinders selectively, reducing the engine’s need for fuel.
Unless you’re driving a Smart Fortwo, sustained cruising down the highway requires only a fraction of the engine’s available power. In this situation, Ecotec 3 engines ‘turn off’ half of their cylinders while nobody’s looking, to help cut down on needless drinking.
How’s it work? Advanced engine controls cancel fuel injection to these cylinders, and a hydraulic valve control mechanism keeps the intake and exhaust valves on the deactivated cylinders closed. In this situation, gases in the deactivated cylinders are compressed over and over again, resulting in a ‘gas spring’ effect that helps the four running cylinders operate more easily.
The entire system is computer controlled, and actuated by solenoids and oil pressure. It’s invisible to the driver, other than a small display in the instrument cluster that references the engagement of four-cylinder mode.
“We chose to keep the proven capability of our larger V8 truck engines, and save fuel by switching off half of the cylinders when they aren’t needed” said Jordan Lee, global chief engineer for small block engines.
He goes on to further diss Ford.
“Rather than adapting a V6 intended for use in passenger cars, we built a new engine from the ground up based on the unique demands of a truck. Sierra’s 4.3L engine shares its basic design architecture with the latest iterations of the V8 engines that GMC owners have trusted for generations”.
Interestingly, GM officials say their AFM technology allowed them to stay away from a smaller-displacement, turbocharged engine (a la Ford Ecoboost) for long-term durability. Drivers will also benefit from a proper exhaust note at full throttle, which is not a characteristic of the Ecoboost mill from Ford.
A cam-phaser, which drives the ECOTEC 3 engine’s VVT system. Click image to enlarge
Variable Valve Timing (VVT): Valve timing regulates an engine’s breathing with a direct effect on power and fuel mileage. An engine with breathing set up for maximum efficiency isn’t particularly powerful. Conversely, an engine with breathing set up for power isn’t typically fuel efficient.
The Ecotec 3 engine line includes VVT technology, which allows these characteristics to peacefully co-exist, since it can actively change the way the engine breathes in real time. Plenty of on-demand power is created when needed, and fuel mileage is maximized when it’s not. The switching between ‘fuel efficient’ and ‘high-performance’ engine breathing is seamless and instant – and the end result to the driver is a potent performance punch alongside reduced visits to the gas station.
Like AFM, the VVT system is computer controlled, totally invisible, and actuated by oil pressure. The VVT system works with a new intake port design that’s rectangular in shape with a slight ‘twist’, which encourages better air ‘swirling’ within the combustion chamber for better mixing of air and fuel.
Direct Injection (DI): With its roots in the world of diesel engines, Direct Injection fuels the engine’s cylinders directly – via an extreme-pressure fuel injector that’s located inside of the combustion chamber.
That’s a sharp contrast to conventional ‘Port Injection’ engines, which spray fuel into the intake tract where it’s simply sucked into the cylinder when the intake valve opens.
By moving the fuel injector inside of the combustion chamber and turning up fuel delivery pressure, engineers can more precisely meter the fuel charge, and ensure a more thorough mix of air and gas ahead of ignition.
Ecotec 3 4.3L V6. Click image to enlarge
Standard on all Ecotec 3 engines, DI technology also allows the safe use of a higher compression ratio—namely 11.0:1 or higher. That’s thanks to a cylinder cooling effect caused by the liquid fuel charge expanding under high pressure. If you’ve ever opened the nozzle of a propane tank or freeze-blasted your buddy with an upside-down can of compressed air, you’ve seen this fun bit of science in action.
In plain English, this built-in cylinder cooling effect makes it easier to run a higher (more efficient) compression ratio, as it combats engine knock, which is caused by heat – but without the need for high-octane gas.
Engineered Combustion: For the Ecotec 3 engine range, GM’s smarty-pants engineers hung out with a bunch of supercomputers for a couple of million ‘CPU hours’ to analyze and design the perfect shape and placement of combustion chamber components for maximum energy extraction from every droplet of gas. In addition to the unique ‘swirled rectangle’ intake port shape, they came up with a uniquely sculpted piston dish, and optimized fuel injector and spark-plug placement.
Officials say more than 100 iterations of the combustion systems were evaluated through computer modeling, before a final design was selected for each engine. 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 hours.
Other Improvements: Technologies like Direct Injection and Active Fuel Management often steal the spotlight when it comes to saving gas, but the Ecotec 3 range also gets numerous other touches that incrementally trim away at consumption.
For instance, a revised cooling system and improved engine-bay sealing allow the engine to heat up and achieve maximum mileage more quickly. A humidity sensor signals the engine computer to slightly modify combustion characteristics to combat the negative effects of atmospheric dampness, and a unique, integrated Positive Crankcase Ventilation (PCV) system helps the engine oil stay nice and slippery. There’s even a variable-displacement oil pump that reduces energy use when its full capabilities aren’t needed.
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