tubbymother

I have searched the archives for a difinitive answer to the following question but have been unable to find it: what is the Mazda manual's specs for a compression test performed on a 12A?

Some of the archives suggest that 70 lbs. is good, while others say 80 lbs. is poor. Moreover, some say the front and rear rotor figures should not vary by more than 20 lbs., while others say 10 lbs.

I know the higher the better, but I would like to know the range: excellent, good, poor, and rebuild.

Thanks for your input.

Makenzie71

last few cars I tested were well over 100.

coldy13

It all depends on the tester you are using. When you use a piston engine tester with the valve held in, then it might only show 70-80 when the engine has good compression(110). The main thing to check for is the range between the different rotor faces and between the 2 rotors. I've tried two different testers on my car, one showed 110 +/- 3 on all faces. The other showed 75 +/- 2 on all faces. As long as the range is good and you can feel the engine pull strong, then I would say your compression is fine.

tubbymother

Using a rotory engine tester

what is the accepted variance between rotors? +/-2, +/-5 etc.

coldy13

I can't remember if it is +/- 5 or 10, if you search you can probably find it though.