At the end of 1951, a new idea arrived: the creation of DKW engineer Erich Wolf (who had previously been a private builder of race-modified DKW RT 125s). Knowing that mechanical valves could not move fast enough to stop fresh charge from being lost out the exhaust port, he decided to devise a nonmechanical valve based on pressure waves moving in the exhaust pipe. He knew that when the exhaust port opened, it released a pressure pulse of 50 to 100 psi into the exhaust pipe. When that pulse reached the expanding megaphone, its expansion propagated back up the pipe with its sign reversed as a low-pressure wave. That "suction wave" worked only too well, inviting more fresh charge to get lost out the exhaust. So why not place an "anti-megaphone" after the megaphone? It would reflect a positive pulse back toward the exhaust port. If timed to arrive just as the piston was closing the exhaust port, it would stop the loss of fresh charge and maybe even stuff some lost charge back into the cylinder. Thin sheet metal, metal snips, welding, and dyno time were all it took to evaluate Wolf's idea, and soon it was ready for track testing. It worked. German engineers called Wolf's converging cone a gegenkonus or a "counter-cone."