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With the move these days towards direct injection, I wonder if such a turbulence inducing ridge would be of any benefit. For NA engines, the chamber filling help afforded by the partial vacuum generated by the exhaust flow may be somewhat hampered? I am still puzzled why the TT engine in the Z has overlap. It would seem that with the higher intake pressure it would not need it. I read somewhere that overlap results in roughly a 20% increase in fill volume. A German replica of the 1903 Wright bros. engine built in 2003, produced double the original HP, when tuned with modern spark and overlap knowledge. I remember porting my HD heads and installing a cam. My engine was lack luster. Retarding the spark and replacing the carb made a world of difference. It is amazing how sensitive motors are to a/f mixture. Did you ever "tune" a glow plug model airplane engine?
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