The air dryer removes moisture from the compressed air for the brakes. The majority of air systems are controlled by a governor valve—a mechanical valve that switches between two preset pressures. No consideration is given to the engine driving mode or the most efficient time to draw power from the engine to drive the compressor.
With a smart air dryer, the air pressure in the reservoirs is monitored by a pressure sensor, and in addition, the vehicle CAN bus is monitored to determine the driving state of the vehicle/engine. The system determines when the vehicle/engine is in an over-run or coasting phase and operates the compressor most efficiently during these phases. New smart air dryers assist in optimizing when to run the air compressor and purge the moisture from the air system.
The study team developed a Confidence Matrix, an OEM Availability Matrix and an Engine-driven Accessories Power Use Chart to assist fleets. The Confidence Matrix is designed to inform fleets of the study team’s confidence in the technology being studied vs. the payback the fleet should expect to receive from the technology. Technologies in the top right of the matrix have a short payback, usually thanks to their low upfront cost, and moreover are found to have enough performance data that fleets can be highly confident in those short payback times, usually because the technology is more mature or otherwise has a more substantial track record of results. The OEM Availability Matrix shows the current availability (as of March 2017) of these engine-drive accessories at the various truck builders. The Engine-driven Accessories Power Use Chart shows the various places the energy from fuel is used in a Class 8 truck.