Driving GM's New Hybrid Pickup
It's slick and silent, and its fuel savings will make you think you're pretty smart if gas prices keep soaring.
Tom Berg
Equipment Editor
General Motors brags that its new Hybrid truck is the world's first full-size hybrid-powertrain pickup to go into production. GM says that it's part of the solution to higher fuel costs and concerns about emissions. But I look at it as something that automatically does what I already do at long traffic stops: shut off the engine to save fuel.
My family thinks I'm nuts, but hey, gas is at $2-plus a gallon out here in California. OK, sometimes I'm embarrassed when a green light catches me with the motor off and I fumble to get it going before the horns behind me start beeping. But I'm saving on gas, right?
GM's Hybrid, on the other hand, is smooth and effortless. Electronic controls sense when the truck is coasting or coming to a stop and switch off the engine, then restart it instantly when the driver's ready to go again. "It's seamless," says Chuck Jones, marketing manager for the Hybrid, because the pickup is otherwise a standard GMC Sierra 1500 with a Vortec 5300 V-8 and Hydra-matic.
But there's more. Instead of a standard starter and alternator, the Hybrid has a 15-kilowatt motor-generator mounted between the engine and transmission. It's a motor when it quickly and quietly cranks the engine without the "eh-eh-eh-eh-eh" of a normal starter. And it's a generator when it captures braking energy and converts it to electricity, which is stored in a bank of three lead-acid batteries under the back seat.
The motor-generator and deep-cycle batteries operate at 42 volts, while most of the rest of the truck's electrical system - including lights, stereo and a battery under the hood - run at 14 volts (what we traditionally call a 12-volt system).
While coasting at moderate speeds, "regenerative braking" causes the truck to drag noticeably against the drivetrain as it turns the motor-generator to produce the electricity. Current stored in the special batteries runs an electro-hydraulic pump for the power steering and a vacuum pump for power brakes, even when the engine's switched off. Air conditioning continues to run in the engine-off mode, too, but the engine restarts to run the compressor when necessary.
Stored power can also be inverted into 2,400 watts at 120 volts and 20 amperes, to operate anything from a popcorn machine at a picnic to a power saw at a job site, or to recharge the batteries for your cordless toys and tools. You plug things in at either of two standard household-type outlets - one in the back seat and another in the right-rear wall of the bed.
Appliances will run for about 36 hours, which is how long the engine will idle before it consumes 24 of a full tank's 26 gallons of gasoline, Jones explained. The engine must run to keep the batteries charged, but the horn will sound when the tank's down to two gallons and the engine will stop. Power will also cut off at some point to preserve enough voltage to restart the engine.
How long would the batteries last with the engine off?
Jones didn't know because the system's not designed to operate that way. "We'll have to do some testing on that," he said.
Unlike other hybrids, GM's doesn't use stored electrical power to turn the motor to propel the vehicle. That's why GM calls it a "mild" hybrid, and why its targeted fuel savings is a mild 10%, which would boost the combined city-highway mileage rating of a 1500 pickup from 17 to 19 mpg, Jones said. Thus it would take a long time to pay for the Hybrid's list-price premium of $2,200. But if gas goes to $3 per gallon by sometime in '05, as some experts predict, the savings would add up more quickly.
At any rate, driving the Hybrid was a high-tech experience - at least at low speeds with the stereo off and the windows up. With the cab silent I noted the savvy system's ability to sense the movements of the vehicle and its brake and gas pedals. As I braked and speed dropped to an indicated 15 mph, the engine quit. It stayed off until I took my foot off the brake pedal. By the time I touched the accelerator, the engine had restarted and was ready to go.
The engine will also sometimes shut off when the truck's sitting still and the transmission's in Park and there's not much electrical load. It'll shut down after as little as 15 seconds, then will restart when the system senses a drawdown of current, or the load on the A/C is high enough to require extra power.
The restarting is quiet and almost instantaneous, and the engine went only to a 600-rpm idle, not the 1,000 to 1,500-rpm surge most engines do when they're started from scratch.
With the transmission in Drive, I felt a soft "thunk" as the starter engaged and a slight "thump" as the specially tuned Hydra-matic quickly reengaged. Then the engine either idled and the truck crept ahead while the traffic ahead inched forward, or revved and propelled me back to cruising speed when I got on the gas.
It also shut down every time I braked slightly while slowly maneuvering through a parking lot, or when I paused at arterial stops in a lightly trafficked residential neighborhood. Does shutting down so often, and only momentarily, make any sense? And won't the numerous restarts wear out the motor-generator? And what would it cost to replace? I decided that it's better not to think about such things, and after a few days I'd probably stop noticing the Hybrid's behavior anyway.
Besides, at any steady speed and any time I was on the gas pedal, the Hybrid drove like any other comfortable and capable GMC Sierra or Chevrolet Silverado half-tonner. The 5.3-liter Vortec V-8 makes up to 295 horsepower and 330 lbs.-ft., so the truck will haul lots of people and cargo and pull a heavy trailer out on the open road. This one was a 4x4 and the push button controls worked smoothly every time I found some dirt to venture into.
True, the Hybrid's special advantages disappear at boulevard and highway speeds. But Hybrid owners will know that they'll encounter traffic sooner or later and will have to stop and start. And that's when they'll again reap the system's benefits.
By the way, stops are gentle because when the engine's shut off, it can't push against the brakes as they're trying to bring the truck to a halt. This is like slipping the tranny from Drive to Neutral just before you come to a stop. Ever do this? It works especially well on snow or ice, and on downward slopes leading to a stop sign. It's another habit I picked up over the years, and yes, you can call me odd, but now I'm vindicated by the slickness of GM's Hybrid and I didn't even have to buy one.
If you're going to purchase a new pickup anyway, the high-tech Hybrid is more than a curiosity and definitely something to look at.
It would be much more valuable if it were a "strong" hybrid with part-time electrical propulsion, and/or included GM's Displacement On Demand system to cut out some of the engine's cylinders under light-throttle conditions.
But if you buy one as it is and gasoline prices soar, savings of even 10% will make you think you're pretty smart.
