its stroke (bottom dead center, or BDC), when the exhaust valve was opened "early". This let the still-hot burnt combustion gases "pop" out of the engine while the piston was still moving down, relieving exhaust pressure and preventing exhaust gases from entering the crankcase. After a small additional amount of travel, the piston uncovered 36 small ports around the base of the cylinder, leading to the crankcase which held additional fuel–air mixture (the charge). No transfer took place at this point since there was no pressure differential; the cylinder was still open to the air and thus at ambient pressure. The overhead valve exhausted directly into the slipstream since no exhaust manifold could be practically fitted to the spinning crankcase and cylinders. The lack of an exhaust manifold also saved weight and prevented excessive gyroscopic forces in flight. During the exhaust stroke, scavenging occurred as the air moving past the cylinder exterior lowered the pressure inside due to the direct exposure of the exhaust port to the slipstream. The piston continued its exhaust stroke until top dead center (TDC) was reached, but the valve remained open. The piston began to move down on its intake stroke with the valve still open, pulling new air into the cylinder. It remained open until it was two-thirds of the way down, at which point the valve closed and the remainder of the intake stroke greatly reduced the air pressure. When the piston uncovered the transfer ports again, the low pressure in the cylinder drew in the balance of the charge. The charge was an overly rich mixture of air, which was acquired through the hollow crankshaft, and fuel that was continuously injected by a fuel nozzle on the end of a fuel line, entering the crankcase through the hollow crankshaft. The nozzle was in the proximity of, and aimed at, the inside base of the cylinder where the transfer ports were located. The fuel nozzle was stationary with the crankshaft, and the cylinders rotated into position in turn. The compression stroke was conventional. The spark plug was installed horizontally into the rear of the cylinder at the top but had no connecting high-voltage wire. An internal-tooth ring gear mounted on the engine drove a stationary magneto mounted on the firewall, whose high-voltage output terminal was in close proximity to the spark plug terminals as they passed by. This arrangement eliminated the need for