GM: new Sierra 5.3L V-8 EcoTec3 highway fuel economy tops Ford EcoBoost V-6

2014 5.3L V-8 EcoTec3 AFM VVT DI (L83) for Chevrolet Silverado and GMC Sierra. Click to enlarge.

The 2014 GMC Sierra 1500 full-size pickup truck features a new 5.3L EcoTec3 V-8 engine equipped with direct injection, cylinder deactivation (AFM) and variable valve timing to achieve EPA estimates of 16 mpg city (14.7 l/100 km) and 23 highway (10.2 l/100 km) with two-wheel drive or 16/22 mpg (14.7/10.7 l/100 km) with four-wheel drive.

In addition to highway fuel economy estimates that are 2 mpg higher than a 2013 Ford V8 pickup equipped with a 5.0L Ti-VCT V-8 and 3 mpg higher than a Ram V8, Sierra’s new V-8 highway fuel economy estimates also measure higher than those of the 2013 Ford F-150 EcoBoost V-6 (23 mpg for the Sierra, 22 mpg for the Ford EcoBoost F-150), GM noted.

2WD Pickup truck fuel economy comparisons
Model	Engine	Fuel economy		Power (hp)	Torque (lb-ft)
		City mpg	Hwy mpg
2014 GMC Sierra	5.3L EcoTec3 V-8	16	23	355	383
2013 Ford F-150	5.0L V-8	15	21	360	380
2013 Ford F-150	6.2L iVCT V-8	13	18	411	434
2013 Ford F-150	3.5L EcoBoost	16	22	365	420
2013 Ram 1500	5.7L HEMI V-8	14	20	395	407
2013 Ram 1500	4.7L V-8	14	20	310	330
Source: GM, Ford, Model Year 2013 EPA Fuel Economy Guide.

With an SAE-certified 355 hp (265 kW) and 383 lb-ft (519 N·m) of torque—increases of 40 hp and 48 lb-ft compared to the 2013 model—Sierra’s new 5.3L offers towing capacity of up to 11,500 pounds.

Most GMC owners—three out of four last year—will opt for the 5.3L V-8 engine, which is an $895 option, according to GM.

The 5.3L EcoTec3 V-8 is one of three more efficient new engines for the Sierra; a 4.3L EcoTec3 V-6 is standard. Sierra also will be available later this year with a new 6.2L EcoTec3 V-8 with more power, torque and capability than the 5.3L. Additional specifications for the 6.2L will be released later.

EcoTec3. Announced in December 2012, the new 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.

The EcoTec3 engines use direct fuel injection 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.

Cylinder deactivation, also known as Active Fuel Management (AFM), is now standard on all three engines for the Silverado and Sierra 1500.

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.

Source: Green Car Reports