Here’s a comparison of the 1.8, 2.0, and 2.5 engines in the MX-5 NC, tested on the same dyno.

All engines:

• Stock camshafts
• 4-1 exhaust headers without a catalytic converter (1.8 and 2.0: Weldman, 2.5: IgorGiera)
• My RomDrop remap
• 5-speed transmission in all cases, measured in 4th gear
• regular fuel (in Poland called 95 octane)

The measurements were taken at different times, but in all cases, the recorded test conditions (temperature, air pressure) were used to apply corrections.