“A Study of Factors Affecting Carburetor Performance at Low Air Flows” 690137
Carburetor repeatability at idle was investigated both on the carburetor precision flow stand and on a chassis dynamometer equipped with exhaust emission test equipment. It was determined that some factors which significantly affect idle fuel flow repeatability on the carburetor test stand are:
Surface roughness of mating parts in the fuel bowl inlet system.
Inlet valve eccentricity.
Hydraulic shock in the fuel supply circuit.
In addition, vehicle testing had demonstrated that carbon monoxide changes at idle may occur with constant fuel-air ratio due to changes in fuel temperature. Cycle tests have also shown a relationship between fuel temperature and carbon monoxide levels.