A device to allow internal exhaust gas recirculation through variable camshaft timing was tested to determine its effects on exhaust emissions. This device made use of a vacuum diaphragm and associated circuits to vary the position of the camshaft in relation to the crankshaft as a function of engine load and speed. The vehicle used was a 1970 Plymouth Fury with a 383 cu. in. engine and automatic transmission. The following tests were conducted: (1) the 1970 Federal emission test procedure as used for certification of new motor vehicles (7-mode); (2) a closed, constant volume sampling technique using nine repeats of the Federal emission test cycle (9-CVS); (3) a closed, constant volume sampling technique using the LA4-S3 driving schedule as specified for 1972 and later. The following conclusions were drawn from the results: The variable cam timing device shows improvements in oxides of nitrogen; The use of this device would not meet 1973 emission levels except for oxides of nitrogen; This system appears to be more effective than external exhaust gas recirculation for oxides of nitrogen control.

"October 1970." "71-11." "Division of Motor Vehicle Research and Development, National Air Pollution Control Administration, Department of Health, Education and Welfare." PB-218 643. APTIC No. 49692.