The methods presented in this document apply to the controlled testing of low temperature charge@ air cooled@ heavy duty diesel engines. This document encompasses the following main sections: a. Definitions of pertinent parameters. b. Vehicle testing to determine typical values for these parameters. c. Description of the setup and operation of the test cell system. d. Validation testing of the test cell system. While not covered in this document@ computer modeling of the vehicle engine cooler system is recognized as a valid tool to determine cooler system performance and could be utilized to supplement the testing described. However@ adequate in-vehicle testing should be performed to validate the model before it is used for the purposes outlined. The procedures makes references to test cycles that are prescribed by the United States Environmental Protection Agency (US EPA) and are contained in the code of Federal Regulations. The existence of other international test cycles@ which can be used for validation testing@ is acknowledged. PURPOSE The primary purpose of this document is to aid in the setup and evaluation of a low temperature charge air cooler system for use with heavy duty diesel engines (HDDE) in dynamometer test cells. These charge air cooler systems typically provide cooled@ charge air temperatures lower than jacket water after cooled systems but above ambient temperature. Examples of low temperature charge air cooler systems include air-to-air after cooled and low flow coolant after cooled systems. While this document addresses emissions evaluation of such engines@ it is not limited to that use.