Engine cylinder exhaust port

An internal combustion engine including means defining a cylinder closed at one end, an exhaust port communicating with the cylinder through said closed end and a poppet exhaust valve disposed in the port and having head and stem portions reciprocable on an axis for controlling communication of the exhaust port with the cylinder, said exhaust port being characterized by

• a throat portion of generally circular cross section aligned with said axis, said throat portion opening into the cylinder and adapted to be closed by the exhaust valve at the cylinder closed end,
• an exit portion having a floor spaced closely to the throat portion and extending at a sharp angle to the direction of the axis, and
• a connecting portion smoothly joining the throat and exit portions and including a convexly curved wall portion smoothly connecting said floor with the adjacent part of the throat portion,
• said connecting and exit portions having a flow guide comprising a free standing bump laterally centered in and narrower than the floor and adjacent curved wall portion, said bump rising in the direction of airflow away from the cylinder smoothly upward from the curved wall portion to maximum height near its leading edge at the throat of about one-third the port height and then curving downward in an extended portion smoothly blended with the port floor whereby the central portion of gas flow in the sharply curved portion of the port is aided in rounding the curve without turbulence, thereby increasing the capacity for flow of exhaust gas through the port.