Paul,
   I have been following your forum for several months now with great
interest and have learned much from it. I am sold on the rotary. But I
would like to see some discussion of detonation in the rotary engine in
aircraft. I have not seen detonation mentioned. Does it occur or not? Is
the Mazda engine running under conditions far from detonation? Are
precautions needed to avoid it? How vulnerable is the Mazda to
detonation damage? Thanks for any information.

Al Rees

Detonation in a normally aspirated Mazda Wankel engine is rare to
non-existent.
It is common in 3rd gen RX7 engines where people have merely turned up
the boost to generate 400 HP or more without making sure the engine
is getting the proper fuel air mixture and the compressed air is properly
cooled with a large enough inter cooler. If you monitor the intake
charge air temperature and hold it below 140 degrees F one can almost
guarantee you will not have detonation. In case you do get it the 3rd gen
RX7 engine's cast iron 3 piece apex seals fracture and score the
expensive rotor housings. There are some 3 mm steel seals on the
market that are way less prone to fracture however they cause more
wear on the rotor housings.

Paul Lamar

Thanks, Paul. I take it this holds for 87 octane auto gas.

Al Rees

Perhaps. I know my RX8 10:1 compression ratio engine runs on 87 auto gas
fine but it does have a detonation sensor. I might check
the OBD II real time output and see if I can record the
ignition advance. I think Mazda got such bad PR on the 3rd
gen they put in a knock sensor just in case.

Paul Lamar