FQS IS A MANUAL ADJUSTMENT OF FUEL INJECTION TIMING. THIS SETTING IS USED WHEN WE GET FUEL OF DIFFERENT IGNITION LAG. WHEN A FUEL IS RECEIVED, IT IS SENT TO LAB FOR TESTING. ONCE THE REPORT COMES ALL ITS PROPERTIES ARE CHECKED AND NOTED.
ONE OF THE MOST IMPORTANT PROPERTY IS IGNITION LAG. A FUEL WITH HIGH IGNITION LAG WILL TAKE MUCH TIME TO BURN AND LEAD TO DECREASE IN MAXIMUM PRESSURE IN CYLINDER WHILE THE FUEL WITH LESS IGNITION LAG WILL BURN QUICKLY AND WILL LEAD TO HIGHER MAXIMUM PRESSURE. BOTH THIS SITUATION DISTURB THE PROPER COMBUSTION OF FUEL.
TO OVERCOME THIS PROBLEM, FQS SETTING IS PROVIDED IN THE V.I.T SYSTEM BY WHICH THE FUEL OIL ADMISSION ANGLE CAN BE ADVANCED OR RETARDED.
THE ADVANCE OF THE BEGINNING OF INJECTION WILL RAISE THE MAXIMUM PRESSURE. NORMAL POWER AND FUEL CONSUMPTION CAN BE RESTORED. FQS IS USED ONLY FOR REGULATING THE MAXIMUM CYLINDER PRESSURE AND TIMING WHERE IT SHOULD OCCUR WITH RESPECT TO PISTON TRAVEL.
FQS SETTING CAN ADVANCE OR RETARD ONLY MAXIMUM TO 2°. THIS IS BECAUSE IT IS A MANUAL SETTING, IF BY MISTAKE THE SETTING IS SET FOR MUCH ADVANCE INJECTION WHICH WILL RAISE THE PRESSURE AND CAN DAMAGE THE ENGINE.