A bad heat range spark plug can ruin your whole day and
        lead to loss of power and a broken apex seal. I have formated
        the thread on on this subject and uploaded it to the web site.
        Please read:http://www.rotaryeng.net/ignition.html

        "All about spark plugs for rotary engines."

        Thanks to Joe Hull for discovering this.

        If anybody has anything else to add please upload your
        thoughts.
        --
        Paul Lamar ...No rotor no motor.


    Ok,
    I've got a '93 13BREW, normally aspirated, with the original rotors-9/1
    compression. The spark plugs I have in it are NGKs  the leading splugs
    are BUR7EQ(Leading), and BUR9EQ(Trailing). They are brand new, and I
    think they are what are recommended as stock in the auto application.
    Should I go to BUR9EQ leading and BUR11EQ Trailing?

    Anyone?

    Thanks

    Brian Trubee

    I would use them while you are running the engine on the ground.
    When you get ready to fly install the colder plugs.
    http://www.rotaryeng.net/Spark-plugs/plugcolorchart2.html

    Paul Lamar ...No rotor no motor.

At Paul Yaw's recommendation, I have been running the NGK B9EGV in my 20B;
9.0 : 1 rotors, NA.  This is an unshrouded plug. I am very pleased with the
performance, particularly that it has no problem clearing after flooding.  I
changed them out after about 30 hours, and find that they are still in good
shape, but have a bit darker color and more carbon deposit than I'd like
Leading and trailing look very much the same.

That first 30 hours had a lot of tuning time (ground running and low power),
which could account for the deposits, but the use included about 18 hours of
flight, and there had been about an hour of flight just prior to removal.  I
replaced with the same, and will check again later; but if the condition is
the same, I'll try a lower heat range (hotter plug)

Al

I just talked to Dave Lemon owner of Mazdatrix and he sells the complete
heat range of NGK spark plugs.

BTW Dave won three out of four SCCA road races he ran this last weekend
in his 2nd gen RX7 convertible until his Paul Yaw front spindle broke :)
Sorry Paul :)