IMPROVED EFFICIENCY POWERED BY GEN IV SMALL-BLOCK V-8
A new generation of GM’s legendary small-block V-8 engine is the power behind the new Chevrolet Tahoe. It delivers improved fuel efficiency (compared to previous generation vehicles) through advanced technology such as Displacement On Demand and other vehicle refinements.
Fuel efficiency-enhancing refinements to the powertrain, as well as improved vehicle aerodynamics, help provide what is expected to be the segment’s best fuel economy. Testing with a 5.3L V-8-equipped model indicates unadjusted combined fuel economy ratings of 20.5 mpg with the 2WD model and 20.1 mpg with the 4WD model. This is better fuel economy than any other full-size SUV.
The Gen IV small-block Vortec V-8 engine family is standard in all Tahoe models, with the 5.3L version standard at start of production. It is rated at 320 horsepower (238 kw)* and 340 lb.-ft. of torque (470 Nm),* an 8 percent horsepower increase compared to the previous 5.3L engine. A Flex-Fuel E85 version, which is capable of running on E85 ethanol fuel or a mixture of E85 and gasoline, is standard on 4WD models and available on 2WD models. E85 is comprised of 85 percent ethanol, which is a renewable resource fuel produced in the United States .
A 4.8L V-8 engine, rated at 290 horsepower (216 kw)* will be standard on Tahoe 2WD models later in the ’06 model year. All new Vortec engines represent the fourth generation of the small-block V-8, which debuted in 1955. Highlights include:
Revised cylinder block design
Displacement On Demand on 5.3L engine
Electronic throttle control
58X ignition system
New, more powerful E38 32-bit controller
Enhanced quietness and smoothness
Returnless fuel system
Gen IV Vortec engines are designed to provide improved fuel economy and reduced emissions, compared to previous-generation small-block V-8s. The 5.3L engines with Displacement On Demand (DOD) technology provide up to seven percent increased fuel efficiency when measured against a comparable non-DOD 5.3L engine. DOD can temporarily shut down the combustion process of half the engine’s cylinders under certain driving conditions to save fuel. GM was the first manufacturer to offer this fuel-saving technology on trucks.
A sophisticated engine controller determines when to deactivate cylinders, allowing the engine to maintain vehicle speed in lighter-load conditions such as highway cruising. The process is seamless and virtually imperceptible. When the cylinders are deactivated the engine effectively operates as a V-4. The engine returns to V-8 mode the instant the controller determines the vehicle speed or load requires additional power. The key to DOD’s efficiency and virtually imperceptible operation is a set of special two-stage hydraulic valve lifters, which allows the lifters of deactivated cylinders to operate without actuating the valves.
Tahoe’s new Gen IV small-block engines also meet more stringent emissions standards. Compared to truck engines of a decade ago, the Gen IV Vortec engine family is approximately 90 percent cleaner. Cast iron exhaust manifolds matched with dual close-coupled catalytic converters help reduce cold-start emissions (the largest source of vehicle emissions).
Quiet, durable operation
All Gen IV small-block Vortec V-8 engines are designed for quiet operation, which contributes to the new Tahoe’s more civilized and quieter driving experience. Engine quieting features include:
Special friction-reducing coating on piston skirts
Full floating piston pins
Damping patch on the oil pan
Timing chain tensioner
Quieter alternator
Acoustically tuned engine cover
Stronger engine cradles and mounting systems help reduce vibrations transmitted through the chassis that would otherwise be felt by passengers. Backing the new engines’ quietness is the assurance of long-lasting performance. The new Gen IV engines were validated under extreme conditions, with dynamometer testing equivalent to 150,000 miles.
Tahoe’s 5.3L and 4.8L powertrains are teamed with the Hydra-Matic 4L60-E electronically controlled four-speed automatic transmission. Backing the engine and transmission team is an enhanced rear axle system that supports the increased power and capabilities of the Gen IV powertrains. They are mounted to the chassis with stiffer brackets and special bushings that help reduce noise and vibration
A limited-slip axle is available, as is a locking differential. Axle ratios range from 3.23:1 to 4.10:1. A new, low rolling-resistance/low-friction pinion bearing design is used to help reduce driveline friction and enhance fuel efficiency. The rear axle carrier has thicker, stronger tubes and the rear cover pan is 50-percent thicker than previous designs.