"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
   weight 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

Mazda used carbon impregnated aluminum for a while. Light so it did not cause chatter
marks on the rotor housing. They also were not hard on the chrome housing  for wear.

Dale Davies


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