SCOPE OF PROGRAM This program was designed to relate the effects of fuel composition on exhaust composition from vehicles equipped with various types of emission control systems@ and in turn to relate the effects of exhaust composition on photochemical smog manifestations. The principal effects are presented in terms of aromatic/olefin/paraffin content of the fuel and exhaust. The smog manifestations of principal concern were ozone formation@ aerosol formation@ and eye irritation. Prior to studying the complex effects of auto exhaust@ studies were conducted to validate the operation of the car used in this program@ the sampling and transfer systems@ and the conditions and operations of the smog chamber. Four nonleaded fuels were used in the major part of the program@ with two additional nonleaded fuels in the latter part of the program. These fuels were used with the project car@ a 1971 Chevrolet 350 CID@ 8-cylinder engine@ and with a 1969 Plymouth equipped with nonproduction exhaust gas recirculation (EGR). The exhaust was generated via the 23-minute DHEW Urban Dynamometer Driving Schedule (LA-4 cycle). This exhaust was diluted about 10:1 in an exhaust tunnel and fed into a large holding bag where the exhaust was usually further diluted another factor of two@ a portion of the exhaust was then fed from the holding bag to the smog chamber - usually at an exhaust hydrocarbon loading of 8 ppm C. With exception of a series of experiments in which the chamber was operated dynamically@ Battelle's 610cu-ft chamber was operated in a batch-wise (static) mode. Chamber reactions were monitored for the standard smog parameters@ including total hydrocarbon@ NO@ NO2@ O3@ CO@ SO2@ PAN@ formaldehyde and total aldehydes@ as well as eye irritation and aerosol content (light scattering) and condensation nuclei (CN) count. Detailed chromatographic analysis of the exhaust hydrocarbon was conducted at three times during the smog reaction@ usually at the start@ midway@ and near the end (5 to 6 hours) of the experiment. Profiles of the chamber runs and tabulations of the detailed GC hydrocarbon data are presented in Appendixes D and E. Two statistical routines@ regression analysis and AID analysis@ have been applied to all the principal smog data generated in this program.