The system allows optimum timing of intake valve operation. The blue line rises sharply as the intake valve closes. Its only weakness was the intake valve seals. This involves closing the intake valve midway through the intake stroke. The intake valve is typically a reed valve. The intake valve was and exhaust valves were . Porsche introduced VarioCam Plus which added two-stage intake valve lift to its VarioCam system. Differences include bore and stroke, intake valve size, and smaller combustion chambers. The snorting is caused by atmospheric intake valve used on many of these engines. The 582 features liquid-cooled cylinder heads and cylinders with a rotary intake valve. The intake valve is actuated by camshaft via the intermediate shaft. The SHO V8 has a split port style intake valve setup. The mixture enters the cylinder through an intake valve at the top of the cylinder. The intake valve closes at point 1. Valvematic varies the intake valve lift between according to load and RPM.