"Detonation" is the spontaneous ignition of the fuel air mixture. This
    occurs after the planned ignition event and usually at a location
remote
    from the spark plugs. So, mixture temperature is usually to blame. So,
    the use of intake air coolers and intercoolers on super charged and or
    turbo charged engines. In order to reduce intake air temperatures.
Also,
    additional fuel my be added to help reduce charge temperature.Also,
    lower compression rotors or pistons may be used.  Also ignition advance
    may be pulled out as boost is going up. Flame front speed is largely a
    function of cylinder pressure.
    So, the higher the cylinder pressure, the faster the burn, and less
    advance is needed to get best cylinder pressure near 50 degrees after
    TDC. Ceramic seals hold up well to detonation. Steel seals and carbon
    seals do not.

    "Preignition", is an ignition event that occurs before the planned
    ignition event. Unlike detonation, it often occurs at or near the spark
    plugs. Usually too high a heat range (plug tip overheats and becomes a
    glow plug). Running the ideal mixture for best power is very popular.
    However with best power comes highest cylinder temperatures and the
    least amount of cooling oil. When leaning to lean of peak operation,
    move quickly through ideal and get to lean. The more powerful the
    ignition system the leaner it will run without missing. Faulty
    distributor cap, plug wires too close together. Primary wires not
    shielded from secondary wires. Solid conductor secondary wire (Use
    inductive secondary wires in most cases).

    You can induce both problems at one time.

    One outstanding feature of the ceramic and the carbon seals is that
they
    weigh nothing compared to steel seals.So, they will track the chrome
    well up into stupid RPM. For above stupid RPM, multiple springs can be
    installed with still no chrome damage.  Also there is just a one piece
    seal, so no pesky corner piece to overload one iron face. Carbon and
    ceramic seals must be fitted to each housing using a diamond file.
Check
    with supplier for specs.
    With both carbon and ceramic seals after years of racing show no
wear at
    all on chrome faces. Ceramic seals stay as new and carbons last about 2
    years.

    Lynn E. Hanover


    This is a piston engine Lynn. What is the source for this definition.

    I would say for an aircraft engine the extra cost of Iannetti apex
seals
    is essential.
    For turbo charged Mazda Wankel the iron seals are marginal.
    Steels seal are not to be used if you expect your engine to last.


    Paul Lamar

    Lynn,

    What material are you referring to citing 'carbon' for apex seals.
We know ceramics, steel and cast iron.
    It could not be plain carbon. It has to be reinforced with
something to prevent breakage and also wear.

    Please elaborate what you are referring to and who makes and sells
carbon seals?
    I know that in Germany firms have tried to use carbon as piston
seals. It did not make
    it to mass production as far as I am aware of. I trust to much wear
was an issue. ?

    Thank you
    Rolf Pfeiffer

     Carbon apex seals are available from the Mazda competition
department. It is no mystery
 at all. Early Mazda rotaries all had carbon seals. They were about 6mm
wide. We machined
them down to fit in the later rotors. You have to be racing a Mazda in
order to buy from Mazda Competition.

Lynn E. Hanover


HI,

I recall doing a complete lap of a test track after first switching the ignition off and throwing the keys to my test observer at the side of the track.

These was in the older Norton aircooled days. Circa 1980.

This phenomena was made worse due to a nodule build up on the spark plug/s and was worse if the test imeadiatly followed a sustained steady state running test.

Hitting the ignition kill switch was a standard part of our test pass off and was carried out normally in third gear at just prior to the rev limiter.

But only for a few seconds, not by throwing the keys away, as that was only done by me to prove to an incredulous engineer that would not believe what I was reporting.

Bob Rowley.

Your plugs must have glowed :-)

Mazda's have been run on glow plugs.

Most diesel engines have them for starting when cold.

I run my model airplane engines on glow plugs and nitro methane fuels.

You weren't cheating on the fuels where you ? :-)

Paul Lamar


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