Engine Compression

Ensure battery is fully charged and engine is at normal operating temperature. Allow engine to cool for 10 minutes. Remove spark plugs and disconnect ignition coil primary connector.
Hold throttle valve fully open during test. Attach compression gauge and crank engine until maximum pressure is reached at each cylinder. See COMPRESSION SPECIFICATIONS table. Lowest cylinder pressure should be at least 75 percent of highest cylinder pressure.

COMPRESSION PRESSURE SPECIFICATIONS ⁽¹⁾

Application

Minimum psi (kg/cm² ) @ RPM

Standard psi (kg/cm² ) @ RPM

Miata (1.6L)

135 (9.5) @ 300

192 (13.5) @ 300

Protege (1.8L)

SOHC

121 (8.5) @ 300

173 (12.2) @ 300

DOHC

128 (9.0) @ 300

182 (12.8) @ 300

323 (1.6L)

135 (9.5) @ 300

192 (13.5) @ 300

⁽¹⁾	Difference between cylinders should not exceed 28 psi (2.0 kg/cm² ).