Mazda Compression Tester

[Weaver7]

Awhile ago we took our compression reading and they came up as.

Front Rotor: 7.9
Rear Rotor: 7.4

This was taken using the factory compression guage. Thoughts/opinions on these readings good or bad?

Thanks!

Bill Weaver
ITS RX-7 #63

[C. Ludwig]

The measurements are in kgf/cm^2 which pretty roughly correlates to kpa. 1 kgf/cm^ = ~98 kpa which roughly equals 14.2 psi. Let's just call it one atmosphere at sea level or 14.7 psi @ sea level. Cranking rpm, altitude, hot/cold engine, and if the throttle plates were held open effect the reading. 250 rpm is generally a nominal cranking rev. Faster speeds produce higher results. All that said you are in the 105-115 range on both rotors. Certainly serviceable. If you happen to be using one-piece apex seals this is actually a pretty good number. I wouldn't plan on freshening the engine at this point.

[Weaver7]

Thanks Chris!