The Effects of Engine Variables and Exhaust Gas Recirculation on Emissions, and Fuel Economy - Part IV

Steady state engine mapping data were obtained from a 400 CID, V-8 spark ignition engine at compression ratios (CR) of 9.3 and 8.0. Data were obtained for seven steady-state speed-load conditions and also for one transient condition to determine the effect of compression ratio on fuel consumption at various exhaust emission levels. These speed-load points were selected to represent engine operating points during the CVS-H cycle. Earlier results at high speed-load conditions indicated that lower fuel consumption could be achieved with the 9.3 CR configuration, even when emission constraints for HC and NO_x were imposed. Also at the low speed-load conditions, at high or unconstrained HC levels, fuel consumption was found to be lower at 9.3 CR; but HC emissions could not be reduced as far at 9.3 CR as at 8.0. Finally, all of the speed-load points were combined in time-weighted cycle simulations to compare the two compression ratios by several emissions and fuel consumption criteria.