You may wonder what a Silverado pickup and a Trailblazer sport utility vehicle have in common. Until now the answer would have been little, except that they are both made by Chevrolet.
For 2005, these two gas guzzlers have been chosen to showcase Chevrolet’s fuel improvement technology.
There is a reason why the company has decided to use full-size vehicles to showcase its fuel economy improvements. This is where the largest gains are to be made in mainstream vehicles.
Roughly half the vehicles sold in North America are truck based, while hybrid cars make up about one percent of sales. If you improve a truck’s fuel economy by the eight percent claimed by the Silverado Hybrid, you reduce fuel consumption, exhaust emissions and operation costs significantly over the life of the vehicle. Get it up to the 13 percent that the Trailblazer is supposed to save and the reduction in operating costs grows.
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If both technologies were incorporated into one vehicle, the improvement in fuel could be as high as 22 percent over a regular engine, but these technologies need tweaking and cost cutting before that can happen.
With the Silverado Hybrid, a good part of the fuel saving comes from the engine’s ability to automatically shut down at stop lights.
The other part of the system is the electrical package, which takes over the job of running all electronics and accessories. It has a 10-kilowatt generator-starter, a battery pack and regenerative braking that helps charge the battery.
However, it provides no electrical assist to the engine, which is part of what defines a hybrid; it must use electricity for part of its motivation.
The 42-volt battery runs an electric-powered hydraulic power steering unit and electric engine cooling fans.
There is an auxiliary electric pump on the heater to maintain cabin temperature. In auto shut down mode, the computer handles distribution of all electrical power.
The most interesting application applies to the generator, which can provide power to the 110 volt, 20 amp electrical outlets in the cab and right rear corner of the truck box.
By pushing a button inside the cab, the computer moves a few electrical impulses and you have a generator capable of running power tools in the middle of nowhere.
You could even use it to run vital appliances in the house or barn if there was a power failure.
Chevrolet has more work to do to get this technology up to scratch, so it is probably a good thing that only fleet customers and a few people in California will be able to get North America’s most expensive electrical generator.
The Trailblazer EXT with displacement on demand saves fuel by switching off four of the engine’s eight cylinders when power is not needed.
Chevrolet talks about a 13 percent improvement in fuel economy. In my test drive, the EXT delivered about 12 litres per 100 kilometres in town and nearly 8.9 L per 100 km on the highway.
That was under a light load of two adults and two kids under 10, at a steady speed.
The system is easy to grasp but more difficult to make work.
Solenoids on the valves for four of the cylinders in the 5.3 L V8 engine are activated by a computer to let oil into a passage in the hydraulic valve lifter that pushes a little pin in and out.
This pin lets the hydraulic lifter “collapse” onto a spring that is softer than the valve spring so the valves do not open or close. At the same time, fuel is shut off to the injector nozzles to prevent fuel puddling when the cylinders come back on line.
When there is a load on the engine, the process reverses and the cylinders go back on line.
Because this system is activated only during low-load situations, the shift from one stage to the other is seamless. It takes a portable scan tool to show any change.
The system is so sensitive that a change in wind direction can cause it to switch modes. In one test, the system changed about 40 times in 15 km and neither of us could tell.
I wondered about the potential for uneven cylinder wear. Chevrolet’s engineers said that because the cylinders are off line only under light loads, cylinder wear would remain even for the life of the engine.
In my opinion, this is the way to go for improved fuel economy in a full-size vehicle. The problem is that for 2005 it will only be available in the Trailblazer EXT.
Think about this: if Chevrolet makes the Silverado Hybrid a true hybrid and incorporates the displacement on demand system, we could be looking at trucks and SUVs that get 10 L per 100 km or 28 mpg in town and nearly 7.1 L per 100 km or 40 mpg on the highway.
It may have to be under ideal circumstances, but anything is better than what these things get now.
Charles Renny is a freelance automotive columnist and a member of the Automobile Journalists Association of Canada. The opinions expressed in this column are the personal views of the writer.
