I don't believe I've read any posts on the Rotary Engine site
regarding Wankel compression testing...
Can the current condition of a Mazda engine be reliably
evaluated with a compression test at low cranking speeds?
Would the PSI values be similar to that of a piston engine?

Robin B

There are several ways of doing it that vary with cost.

Plug the lower spark plug hole with your thumb or finger
and feel at least three pulses in a row while turning
the engine over with the starter.

Remove the exhaust manifold and listen for at least
three puffs or huffs in a row while turning the engine
over with the starter. You can use a cheap wind speed
indicator :)

Take a standard piston engine compression tester
and remove the schrader valve. Turn the engine over
with the starter and look for at least 3 pulses in a
row up to 80 psi.

Buy a $100 data acquisitions system  from Hytek Automation
with a $10 pressure sensor from FreeScale Semi and record the
pressure as the engine rotates with the starter. You will need
to make a hose barb out of an old spark plug. See the attachments.

Spend up to $500 with Mazda for a special tool that
does the same thing.

If the compression is good the engine is OK to fly.
No need to take it apart.

Paul Lamar