In 1913 the Seguin brothers introduced the new Monosoupape ("single valve") series, which replaced inlet valves in the pistons by using a single valve in each cylinder head, which doubled as inlet and exhaust valve. The engine speed was controlled by varying the opening time and extent of the exhaust valves using levers acting on the valve tappet rollers, a system later abandoned due to valves burning. The weight of the Monosoupape was slightly less than the earlier two-valve engines, and it used less lubricating oil. The 100 hp Monosoupape was built with 9 cylinders, and developed its rated power at 1,200 rpm. The later 160 hp nine-cylinder Gnome 9N rotary engine used the Monosoupape valve design while adding the safety factor of a dual ignition system, and was the last known rotary engine design to use such a cylinder head valving format.