Ah makes sense I suppose

 

Well, when I bought the car 2 years before I only checked the front rotor. The car had 110000km's and checked it with a regular compression tester with the valve removed blah blah blah... i saw about 120 psi on the dial with even pulses. I didnt check the back as I could tell the car was immaculate and I wasn't worried after seeing that.

When I did check it again with the mazda tester, it was at this years Ottawa meet, so about 5 other cars also tried it out. most were in the 8.0, 8.5, 9.0 range, one even had a 6.5 on the tester. It wasn't my tester so I can't tell if it was calibrated, or if it needed it.

The person who took my plugs out immediately commented on my spark plugs saying they were uncommon because of the whiteness only being to one side of it on the electrode. Then we preceded to the test and I got 10.5 across the board.

Yes, but would I not have detonation, and probably blown apart an apex seal, especially with a -20c cold start and flooring it till it cut out at 4k rpm hammering it into second? (I know this is a stupid thing to do, but you dont need to know why I have done this a couple times already)

I posted this thread to see what others are getting with their motors.... not to blabber about how and why my reading is impossible.

 

The compression varies based on lots of things. Was it checked with the engine warm or cold? At the leading or trailing plugs? At what RPM/altitude?

There's no way a correct reading would give you the exact same number for all faces of BOTH rotors because the RPMs the starter spins the motor at aren't going to be the same. All I'm saying is the test should have been duplicated a time or two, I have the same tester and sometimes have to jigger with the adapter before I get repeatable correct numbers.