The Chrysler Method of Carburetor Idle Flow Correlation

In the continuing search for reduced exhaust emissions from automotive engines, tighter controls on production carburetor fuel-air ratio delivery became necessary. Idle fuel and airflow measurement assumed major importance due to the influence of idle set points on exhaust emissions and on the part throttle flow curve of the carburetor.

This paper details the development of idle fuel and airflow measurement transfer systems to correlate data between test stations, including the use of carburetors locked in the idle position. Matched sets of sonic flow nozzles are currently in use at each test location as a basis for defining carburetor idle airflow. Fuel flow, using a test fluid developed specifically for this application, is defined by a simple, accurate weight time calibrator.

The current system requires only the transmittal of data between test locations and is now entering its second year of production application.