Parallel Hybrid Truck
GM's latest hybrid experiment is one that shows so much promise, GM has decided to debut the system as an option on '04 trucks equipped with the 5.3-liter V-8. The setup uses an integrated generator mounted in front of the transmission, which charges a 42-volt battery pack during braking. During acceleration, this same generator provides additional torque to assist the gasoline engine in motivating the vehicle. While at idle, the engine shuts down to further conserve fuel and restarts as soon as you touch the accelerator pedal. After testing at least two different trucks fitted with this setup, we can't wait for production units; its operation is seamless. GM says fuel economy is improved up to 12 percent. An added benefit of the system is that when the engine is idling in Park, the generator provides enough energy to power twin 110-volt, 20-amp A/C power outlets mounted in the cab and bed to run power tools and other electrical equipment.--C.S.
Displacement on Demand is made possible by solenoids that control oil flow to special switching valve lifters (shown). When activated, normal valvetrain operation occurs. When deactivated, only half the cylinders operate.
Displacement On Demand
The idea of running an engine on only some of its cylinders isn't new. Former attempts failed mostly due to a lack of accurate control over when cylinders are deactivated and brought back online. Today's sophisticated engine-control computers make it possible to seamlessly deactivate half an engine's cylinders (V-8 becomes V-4; V-6 becomes V-3, etc.) when power isn't needed, but bring them back up when acceleration is needed. We tested a DOD-equipped Chevy Tahoe fitted with a 6.0-liter V-8 and could not tell when it was running on only four cylinders versus all eight. GM says it works well enough to improve fuel mileage between eight and 25 percent depending on driving conditions. Look for it to be available in late 2004 on most '05 Vortec truck and SUV V-8 engines.--C.S.