SOUTHWEST RESEARCH INSTITUTE

Analysis & Simulation

Design

Test and Evaluation Services

Test and Evaluation Systems

Hybrid Vehicle Services

Facilities

Clients

Past Projects

Publications

Contact  Us

SwRI Information

Home

The pumping system used in a step ratio automatic transmission can consume up to 20% of the total power required to operate a typical automotive transmission through the EPA city cycle. As such, the pumping system represents an area on which manufacturers have focused their efforts in their quest to obtain improved transmission efficiency. This paper will discuss the history of automatic transmission pumps that develop up to 300 psi along with a description of the factors used to size pumps and establish pump flow requirements. The various types of pumps used in current automatic transmissions will be described, with a discussion of their characteristics including a comparison based upon observations of their performance. Specific attention will be focused on comparing the following:

• Volumetric efficiency

• Mechanical efficiency

• Overall efficiency

• Pumping torque

• Discharge flow

This paper represents information on a wide cross section of current production automatic transmission pumps produced by manufacturers from around the world. The results in this paper are based upon real-world applications of these pumps and the various compromises manufacturers make so a pump operates across a broad range of operating conditions as required by the transmission.

The conclusions expressed in this paper are based upon a total population of 43 automatic transmission pumps tested at Southwest Research Institute (SwRI) over a 5-year period. From this population a group of 14 pumps used in 3.0-4.0L engine applications was selected. The conclusions drawn about each pump type are based on an average of at least 3 to 4 representative pumps of each type. These pumps included a cross section of pumps of varying quality produced by various manufacturers. The data used to support the conclusions in this report incorporate the entire pumping system and the type of packaging and performance constraints placed upon pump manufacturers producing cost-effective, high-production pumping systems.

For more information about performance comparison of various automatic transmission pumping systems capabilities at SwRI or how you can contract with SwRI, please contact Douglas Fussner at dfussner@swri.org or (210) 522-3972. 

| Design and Development | Engine, Emissions & Vehicle Research Division | SwRI Home |

Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions.

September 30, 2008