The Renesis design features two major changes from its predecessors. First, the exhaust ports are not peripheral but are located on the side of the housing, which eliminates overlap and allows redesign of the intake port area. This produced noticeably more power thanks to an increased effective compression ratio; however, Mazda engineers discovered that when changing the exhaust port to the side housing, a buildup of carbon in the exhaust port would stop the engine from running. To remedy this, Mazda engineers added a water jacket passage into the side housing. Secondly, the rotors are sealed differently through the use of redesigned side seals, low-height apex seals and the addition of a second cut-off ring. Mazda engineers had originally used apex seals identical to the older design of seal. Mazda changed the apex seal design to reduce friction and push the new engine closer to its limits.