[neurotech1]

Its the intake design that makes the difference for supersonic performance.

JT8D [0] is based on the J52 engine that powered the A-4 Skyhawk, and a related design is the RM8 [1] that powered the M2.0+ SAAB Viggen.[2]

[0] https://en.wikipedia.org/wiki/Pratt_%26_Whitney_JT8D

[1] https://en.wikipedia.org/wiki/Volvo_RM8

[2] https://en.wikipedia.org/wiki/Saab_37_Viggen