Chevrolet Tahoe Hybrid Performance
The 2008 Chevrolet Tahoe Hybrid's electric motors struggle to move the SUV at slow speeds, and its braking takes some getting used to. However, it has the same easy ride and handling of the conventional Tahoe.
With this vehicle, General Motors introduces its new "Two-Mode" hybrid system, which has previously only been used in buses. This system, developed in conjunction with BMW and DaimlerChrysler, combines a gas engine and two electric motors via an automatic transmission that incorporates features of a continuously variable transmission (CVT) to find the optimal combination of engine and gear ratio for a number of different types of driving.
Acceleration and Power
The Tahoe Hybrid's gasoline engine is a 6.0-liter V8 that generates 332 horsepower and 367 pound-feet of torque. It includes a cylinder deactivation system that can shut off four of the eight cylinders when they aren't needed. In addition, the Tahoe Hybrid has two 60-kilowatt electric motors that run off a 300-volt battery pack for lower horsepower acceleration or a power boost for the gas engine, usually when the vehicle is in stop-and-go city traffic. The Tahoe Hybrid "was smooth as you please in stop-go," says Jalopnik notes that "a feather foot will keep the Tahoe in full electric mode. A leaden foot brought on the familiar Chevrolet V8 kick, which scooted the monster into motion as expected." However, Car and Driver says, "At the low end, the hybrid feels a bit weak, but it comes on with a surge of power in the midrange" when the gasoline engine takes over., "because the electric motor, which handles low-speed driving, provides all its power the instant it begins to turn."
An important measure of the performance of such a two-mode hybrid system is how smoothly it moves between the gas engine and the electric motors. Edmunds says the transitions "were quiet and smooth, almost imperceptible." The key to these transitions is the automatic transmission. Edmunds explains the transmission is "kind of like a continuously variable transmission (CVT), only there are very sophisticated controls to deliver speed while carefully balancing the amount of power that comes from both the gasoline V8 and the electric motors." The transmission gets good reviews. "The Tahoe may feel even more natural than some other hybrids because it combines fixed transmission gears with the continuously variable nature of a full hybrid," says Cars.com's Kicking Tires blog. "In other words, it shifts just like an automatic transmission, but with some continuously variable changes, too."
The Environmental Protection Agency hasn't rated the Tahoe Hybrid yet, but GM estimates a 25-30% gain in gas mileage over the regular Tahoe in a mix of city and highway driving, with the greatest gains in city driving. Reviewers think this is not only realistic but may even be a conservative estimate.reports on "one mile of straightaway at a steady 50 mph, the 6,000-pound Tahoe delivered 30 mpg, according to an onboard gauge."
Handling and Braking
The Tahoe Hybrid handles much like its non-hybrid sibling. "Ride and handling felt comparable [to] that of regular Tahoes," says Car and Driver. The found the Tahoe Hybrid's ride to be "silky smooth." Car and Driver complains that the steering "has even less feel than the regular Tahoe's." But the disagrees: "Even the electric power steering, which GM has had only spotty success with, was spot-on."
Reviewers take particular note of the brakes, which help recharge the battery that runs the electric motors. Edmunds reports that the Tahoe Hybrid has "regenerative brakes that capture energy normally wasted during braking and use it to recharge the battery." While reviewers are excited about this technology, there is some disagreement as to how well the brakes work at stopping the vehicle. "The feel of this electromechanical brake system ... is lacking," says Car and Driver, "and smoothly braking at your desired rate involves much guesswork." But according to Edmunds, "The Tahoe Hybrid also proved to have exceptional braking performance. The pedal felt firm, and the GM engineers claim the Hybrid comes to a halt in a shorter distance than the conventional Tahoe."