Dual Displacement Power Steering Pump
Power steering pumps typically run all the time to handle worst-case needs of low-speed vehicle turning and maneuvering. Virtually all heavy-duty trucks have power steering systems to assist with the turning of the vehicle when necessary.
The power steering system consists of a hydraulic engine-driven power steering pump, a steering gear, control valves to route the hydraulic fluid depending on the direction of the turn, a small fluid reservoir, and hydraulic hoses to route fluid to the appropriate components. In addition, a fluid cooler is sometimes required to keep the hydraulic fluid in the proper temperature range. The power steering pump turns and generates pressure/flow any time the engine is running.
New systems take into account the fact that line-haul tractors spend the vast majority of their operating hours going nearly straight down a highway when little steering effort is necessary. The dual displacement power steering pump works by using the full displacement available when the engine is at a low speed. Once the engine/pump speed is sufficient, the dual displacement power steering pump automatically switches to the pump with smaller displacement that takes less horsepower to turn.
It is important to note that power steering pumps typically consume 0.3–0.6% of the truck’s fuel to perform their function, so any fuel economy gains from new technology will be modest.
Benefits
Fuel Savings
Lower Power Consumed
Challenges
Not Available from any Truck OEMs as of March 2017
Increased Cost
Increased Complexity
Reliability Concerns
Increased Maintenance Costs