He goes on to say at high RPMS a large time-area for transfer ports creates short circuiting( I assume short circuiting means that fuel gets rammed back into the transfer ports from the strong positive exhaust wave). Jennings states that a small time-area exhausts ports combined with large time-area transfer ports is good combination for broad range/ low RPM power while the opposite is true for narrow range/high RPM power. However, Bell says that higher RPM engines require longer transfer port durations then low RPM engines. He says that the longer the transfer ports are open, the more time is allowed for the negative wave from the exhaust to pull fuel through them (as does Jennings). His port time equations don't even include RPM, You input the dimensions of the engine and it spits out how long the port should be open. Graham Bell starts off by saying that he doesn't believe port time area and its all about the duration the ports are open. Jennings book talks about port time area and porting the cylinder to have peak efficiency at a certain RPM.
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