Universal drum 11 # has been moving at the speed of sound since 1992.
A four stroke engine only opens its valves at the end of the exhaust stroke and at the beginning of the intake stroke after the piston has done work. Due to the short opening time of each valve in high-speed engines, the head of the universal drum is usually made shorter, which can allow the vacuum low pressure to quickly return to the exhaust valve. Low gear engines typically have longer exhaust pipe heads due to their lower engine speeds and longer valve opening times, allowing the vacuum low-pressure belt to take a longer time to return to the exhaust valve.
