HKS ES Premium Cat-Back Exhaust For 2011-2014 WRX/STI Sedan
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ES means Elegant and Premium, and that is exactly what this new HKS exhaust is. It all starts with mandrel bent 304 stainless steel piping from the catalyst all the way to the mufflers. The piping is a full 3 inches back to where the mufflers split and from there each 2.12" pipe feeds into the beautiful ES mufflers.
The ES mufflers have elegant rolled tips and a silent chamber design to keep the droning sound down. This exhaust system also features the new side branch which helps reduce the raspiness sound that is all too common. The side branch uses the theory behind superposition of sound waves. The sound wave is sent through the side branch and is reflected from the end. This reflected sound meets the main system sound wave but is phase shifted which acts to cancel each other out. The net result is that the overall sound level is reduced whilst the design of the side branch does not affect the exhaust gas flow meaning that no performance is lost.