Answer:
The series of the Engine.
The H22 came in many variations.
In the US, the H22A1 was the motor found in Vtec models of the Fourth Generation Prelude.
The H22A4 was found in 5th generation Preludes.
The H22A1 is rated at 187 HP and 158 ft-lbs of torque
The H22A4 is rated at 197 HP and 156 ft-lbs of torque.