Why are you so hung up on 230 mph? The air molecules don't know how fast the hood scoop is going. It isn't like they look at a car and say "it is only going 210 mph so we're not jumping in".

The pressure in a hood scoop will increase with the square of the velocity starting from zero. It isn't a light switch that turns on at 230 mph. There will be positive pressure (greater than 14.7 psi) at any speed above zero. The equation was posted back on page one of this thread.