The 2009 GMC Sierra Two-Mode Hybrid pickup has my undivided attention. As I write this, my wallet is still smoking from doling out $85 to fill my 4-wheel-drive boat-tower, which averages a measly 14 mpg around town and 18 mpg on a long-distance interstate run. The new hybrid is said to get closer to 22 mpg in town—and 20-plus on the road. That’s around 50 percent better, and that equates to a savings of about $4,000 over five years of driving.
GMC (and Chevrolet) will only be offering the Two-Mode Hybrid package in the top-of-the-line models in the first year or two. No prices have been set as of press time, but I expect a top-shelf 4x4 Crew Cab Sierra Hybrid to be north of $45,000; the 2-wheel-drive will be in the high $30s.
Is it worth it? I feel it is for any outdoorsman who puts a lot of miles on a pickup and keeps it for eight to 10 years.
Keeping Utility Intact
Utility is a make-or-break concern for those of us who need a full-size pickup for our lifestyle. GM has kept functionality alive and well, as the hybrid tows a respectable 6,100 pounds, and I expect it will offer improved towing fuel economy.
The one I drove even accelerated stronger and faster than a nearly identical standard model. Here’s why: a special Electrically Variable Transmission (EVT) incorporates a pair of electric motors, three planetary gear seats and four hydraulic wet clutches crammed into the same transmission case as a standard 1500 Series GM pickup. Total available horsepower when the 300 hp 6.0-liter and twin electric motors are at full output—332 horsepower.
This lets the on-board computer instantly provide low-end torque with the perfect gear ratio—either variable electric or four fixed-ratios—to meet any power need while maximizing fuel economy.
“Along with being very smooth, the EVT always provides abundant torque at all rpm levels for easy towing,” says chief engineer Mark Cieslak. “It’s particularly helpful on grades, as the EVT’s greater ratio spread allows the engine to hold optimal rpm for smooth, steady performance, with no hunting between higher and lower gears.
The EVT also incorporates grade braking and tap up/tap down shift control. It benefits towing on curves or lower-speed back roads, as exceptionally smooth gear transitions eliminate “shift shock” torque disruption.
Electric motors do great at lower speeds, but as the vehicle closes in on 40 mph, they become less efficient than the gas engine. GM’s Hybrid Optimizing System (HOS) solves this dilemma.
HOS gets torque-based information from the throttle-position sensors, transmission module, brakes and other systems, then instantly determines the most efficient means of putting power to the ground. That could be using the V8, the two electric motors, or a combination thereof.
Hard acceleration, towing, four-wheeling, or other high-load situations brings the V8 and the two electric motors on-line.
Active Fuel Management
Another cool piece of technology is how the HOS system manages the 6.0-liter Vortec V8. The engine has Active Fuel Management (Mode 1); the on-board computer switches between four cylinders and eight as you drive, based on the throttle and load. The truck runs on four cylinders during light, no-throttle or coasting/idling situations.
GM has had this on its V8s for several years, but this differs in that the HOS allows the V8 to run in four-cylinder mode for a much longer time and with a bit more throttle, as it is helped by the electric motors.
Those electrics are powered by a 300-volt nickel-metal hydride Energy Storage System (ESS), and an on-board charging system always keeps the battery pack hot.
Hit the brakes, and battery charging takes place from the braking process. Cruise down the road, and the ESS uses the gas engine or one or both of the electric motors as a charger.
As a side benefit, the brakes are strong and fast acting because they get a boost from the electric motors as they turn into generators when you lift off the throttle.
In addition to supplying power to the EVT, the ESS powers the air conditioning compressor and Accessory Power Module, which converts the high-voltage supply to 42 volts for the electrical power steering, as well as 12 volts for the vehicle battery and 12-volt accessories.
A little oddity is the gas engine shuts off when you stop. Accelerate lightly and the Sierra will remain silent, moving under electric power to about 30 mph, at which point the V8 purrs to life. Apply more throttle and the V8 engages sooner; the transition is smooth and instant.
It’s not just fuel-economy features like that but rather all of the aspects of the new Sierra that really have my hopes up of again getting behind the wheel before too long.