Traditional water pumps constantly circulate coolant through a series of passages, cooling the engine components from the extreme heat generated through combustion and rejecting extra heat as the coolant passes through the radiator.
New variable speed water pumps do not operate at full power all the time and therefore reduce the load on the engine. Managing pump speed through controls without compromising the cooling necessary reduces the overall horsepower required to drive the water pump.
It is important to note that water pumps typically consume 1.1–1.8% of the truck’s fuel to perform their function, so any fuel economy gains from new technology will be modest.
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-driven 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.