Designed and built entirely in the U.S. from the highest-quality American T304 stainless steel, the CMS Ultimate Exhaust replaces the heavy, restrictive OEM center muffler on your Porsche 991 GT3, RS, or 911 R — any 991 with the center muffler outlet. Engineered specifically to scavenge exhaust pulses, increasing exhaust gas velocity and flow, the CMS Ultimate Exhaust is the only 991 exhaust dyno-proven to add over 14 horsepower and 13 pound-feet of torque at the wheels. By replacing your OEM center muffler with the CMS Ultimate Exhaust, you’re also removing 11 lbs. of rear-end weight.
RACECAR SOUND, NO DRONE
In addition to increased performance, the CMS Ultimate Exhaust makes an incredible snarl at low- to mid-revs that turns into an intoxicating, all-out flat six wail above 6,000 rpm!
Full-throttle volume increases to about 98 dBA, and CMS engineered out any hint of in-cabin drone anywhere in the RPM range, particularly in that 2,000 to 2,500 rpm range that other center deletes tend to exacerbate. Part throttle, full throttle, idle, valves open or closed, no drone. The CMS Ultimate Exhaust sounds like a racecar when you want it to, but doesn’t drive you nuts when you’re just cruising.
EXHAUST FLOW IS KEY
The dual-outlet cross-flow design uses the same scavenging principle used in racing headers. Particularly at high rpm, an exhaust pulse in one side of your exhaust system reaches the CMS Ultimate Exhaust and creates a vacuum in the opposite side of your system, “pulling” the next exhaust pulse through that side of your system. This increases gas velocity, reduces back-pressure and engine pumping losses. The result is increased torque and horsepower. At lower rpm, this effect is less prevalent, allowing mid-range torque to rise as well.
The meticulously engineered design of the CMS Ultimate Exhaust also features a relaxed radius on the curved 4-inch outlets, further improving high-rpm flow. This design eliminates the need for the power-robbing, flow-killing cross pipe that some center deletes implement to try to tame drone. The result of all this attention to detail is CMS Ultimate Exhaust makes power and torque, sounds phenomenal across the rev range, and is actually an engineered part of your exhaust system. Not just a cool bolt-on.
HAND-CRAFTED IN THE USA
Each CMS Ultimate Exhaust is made by us, in our facilities in the United States, by hand by a single expert fabricator from start to finish. Crafted from the highest-quality American 304 stainless steel, it is meticulously finished inside and out, the result of unwavering focus on workmanship, functional design, and premium materials. Every CMS Ultimate Exhaust comes with a durable ultra-high temp 1000° F coating in satin black, satin silver, or satin bronze. $1,495.