The city of Fort Wayne, Indiana, is adding four GM Sierra hybrids to its fleet.
The Sierra are technically micro-hybrids—the system provides start-stop functionality and regenerative braking, but no propulsion support. Overall, the hybrid version delivers up to 10% improvement in fuel efficiency in city driving. On the highway, there is no benefit, as all of the fuel savings come from the start-stop function.
The electric motor can also generate up to 14 kW of continuous electric power. The cab and pickup bed offer outlets that provide 20 amps of 120-volt power for tasks such as the operation of power tools at a construction site.
The 14-kw starter generator motor and torque converter are mounted in a concentric arrangement between the engine and transmission, without requiring additional powertrain length. An auxiliary transmission oil pump helps the automatic start feature by assuring sufficient line pressure to allow torque transfer immediately upon driver command, when the engine is started.
The Sierra also uses an engine-independent electro-hydraulic power steering (EHPS) system to provide steering control even when the engine shuts off to conserve fuel. The EHPS also provides power assist for the brake system’s Hydroboost hydraulic brake booster.
Three valve-regulated lead-acid batteries store power for the 42-volt system. The batteries, stored in a single energy box that is mounted under the rear seat, power only the EHPS and the starter generator. A conventional 12-volt under-hood battery powers all the other normal electrical items, such as lighting, driver information center and infotainment system.