I recently got a compression from the local Mazda dealer. The compression tester read something like 83, 83, 85. Can someone "elaborate" on what this reading means exactly? All they said was, your engine is "good." Kinda makes you feel stupid for paying a hundred bucks to hear someone say your car engine is "good."

 

Those numbers would have to be in PSI, and there should be six of them. 83-85 PSI is about the bare minimum according to the FSM. A strong engine will be at 100+ PSI per rotor face.

 

That can't be right. I am not a mechanic or anything but I believe that certain rotary engines (NA/Turbo) have a compression test number. I think the NA's is 89 and the turbo is 87. Having a number from 83-85 doesn't mean much to me because it's ot 87 or 89. Please correct me if I'm wrong. Anybody?

 

Um, no. That doesn't make any sense at all. Seal condition, air temperature, humidity, compression ratio, etc... determine how much pressure you will measure on the compression stroke, and every engine is different. There is no one single pressure value that every engine will produce. You should do a search for "compression test".

 

the limt as stated above is 85psi per face. the engine will continue to run but you may have difficulty starting it, difficulty with flooding and poor fuel economy (as if it could get much worse). a rebuild is in your future.

 

Are you sure your numbers were not 8.3, 8.3, 8.5?

Mazda Compression testers read out in BAR not PSI. The numbers that I have posted indicate a healthy engine, the ones that you posted (in psi) indicate a tired, worn engine.

Also there should be a total of six numbers for a complete test, one for each rotor face.

 

I'm not sure, I saw from a distance. It's very possible that it read 8.3, 8.3, and 8.5. However, there were only 3 numbers, they said it was an older type of compression tester. One that does not print out a reading or anything.

 

The test needs to be done twice, once for each rotor

Tester would look like this, results should have been on your invoice

 

Yes, that's what it looked like. However, I do not see any results on my receipt. Also, I only witnessed one test. Can I assume they tested the other rotor?