The study of engine performance under different fuel injection timing of a CNG direct injection engine was carried out in a retrofitted car engine. The experiment was performed on a 1297cc, 4-stroke, four cylinder SI engine having compression ratio 9. The base gasoline engine was converted into bi-fuel engine by installing both CNG port injection (CNG-PI) and CNG direct injection (CNG-DI) system in a single gasoline engine. The injection timing was varied from early injection (EI) timing at 220° BTDC to a late injection (LI) timing of 120° BTDC. The experimental study was limited by an engine speed upto 2700 rpm due to high thermal loading at higher speed. The results indicate that, the late injection timing 120° BTDC gives 10-12% higher brake power at a lower engine speed upto 1800 rpm as the volumetric efficiency is better at a lower speed. The optimal injection timing 160° BTDC produces higher performance over the entire speed range from 1200 rpm to 2500 rpm due to sufficient and optimum time available for preparation of CNG-air mixture. The early injection timing 210° BTDC gives very good engine performance for engine speed above 2700 rpm which accelerates better air-fuel mixing at a higher speed.
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.