assalam o alaikum n here r the stats for both of these engines ..
D15B 3-Stage VTEC
Bore and Stroke :75,0?84,5 mm
Displacement : 1,493 cc (91.1 cu in)
Rod Length : 137 mm
Rod/Stroke : 1.62
Compression : 9.3:1
Power : 130 PS (96 kW; 128 hp) at 7,000 rpm[6]
Torque: 139 Nm at 5,300 rpm
VTEC 12-valve to 16-valve switch over : 3,000 rpm (below such engine speed, the engine is operating in 12-valve mode)[7]
VTEC high cam switch over : 6,000 rpm
Redline : 7,200 rpm
Valvetrain : SOHC, four valves per cylinder
Connecting rod length : 137 mm
Connecting rod big end diameter : 48 mm
Fuel Control : OBD2a
Head Code : P2J-07
ECU Code: P2J (small case ECU)***
D16W9 3-Stage VTEC
Bore and Stroke: see D16 Series Engines
Displacement: see D16 Series Engines
Power: 130 hp (96.2 kW, 131 ps) at 6,600 rpm
Redline: 7,200 rpm
Valvetrain: SOHC VTEC3 (4 valves per cylinder)
1st VTEC Switchover: 2,500 rpm
2nd VTEC Switchover: 5,500 rpm
Fuel Control: OBD2
As the stats aboe show D16W9 should be almost equal in fuel efficiency to D15B but it should be more powerful then it due to being 1600cc and having 130HP where D15B is 1500cc and has 128HP
I need some experts to clarify it that why does it happen? and I have seen many D15B civics smoking 7th Generation PKDM VTI civics quite easily .. while both on stock