A method for compressor surge detection to enable model based air estimation includes determining if an intake air compressor pressure ratio is within a predetermined surge pressure range. Then the differences between mass air flow sensor signals measured at a start and finish of each count of a predetermined string length counter when the compressor pressure ratio is within the predetermined surge pressure range. Next, a transition is made to an air mass estimation model output signal from a mass air flow sensor signal when a sum of the air flow differences is greater than a predetermined compressor surge threshold.