Fuel control system and method of engine

The present invention relates to a system which applies a torque-based control to a direct injection engine with a turbocharger (101) and is capable of switching between stoichiometric running and lean-burn running in accordance with a driving state, in order to provide a means for obtaining preferred exhaust performance and driveability, a turbo lag index (300) is computed on the basis of supercharged pressure information or air intake pipe pressure information which are obtained directly or indirectly, and then a throttle opening (301) or a fuel injection quantity is corrected on the basis of the above-described turbo lag index (300) to obtain desired torque and exhaust characteristics. As a result, it is possible to prevent a torque variation, a change in torque characteristics, exhaust deterioration, or the like in a transient time, which are generated due to a turbo lag.