So you did this using a standard compression tester? Though thats' fine, there's a way of doing it properly to get the correct reading.
You need to run multiple cranks to ensure you read all 3 rotor surfaces. Because 1 weak apex seal will cause low compression on two rotor surfaces. So if you just cranked once per housing thats not going to tell you anything.
What you can technically do is, connect an OBDII reader and get the RPM readings so you can do the proper correction in your figures later.
If you're using a standard engine compression tester you should:
1. Connect an OBDII reader and scan for the RPM readings when cranking.
2. Crank multiple times per housing, and make a video out of it so you can later see where compression drops and where it peaks. You take a note of those peak readings and average them out, that will give you a fairly accurate reading of the overall rotor health.
3. Repeat #2 for the second housing.
And now you need to correct for the standard RPM- you can do that by simple math. Compression for Mazda Rotary engines is tested at 250RPM. If your starter motor or battery is weak your cranking RPM can be a lot lesser than 250 RPM. This is the case with a lot of 03-04 (pre June 04 RX8s) RX8s as they had a weak starter motor. If your battery is overpowered, your cranking RPM may be higher than 250 RPM, which can then result in overly high readings. Which would explain why you got 150psi on one rotor.
Ideal 13B-MSP compression (in an ideal world) is 120PSI, which really isn't possible after your wankel has been run in over 4,000 KMs because the apex seals start "settling" in and making their own grooves around the housing, so you do lose compression with this engine over time (premixing really helps in avoiding that).
You can do a basic correction by this math:
If your car cranked at 205rpm, you do:
=> 205/250
=> you get 0.82
=> minus that from 1.
=> You get 0.18
=> You need to then multiply your result by 1.18 to correct the compression figures.
On the other hand if your car cranked at 300rpm, you do:
=> 300/250,
=> you get 1.2
=> then you do 1.2 - 1
=> you get 0.2.
=> Then you do 1 - 0.2
=> you get 0.8
=> You then multiply your result by 0.8 to get the corrected compression figure.
Compression testing a wankel is not easy unless you have a proper Mazda compression tester. The closest you can get to that test is by using my method above.
