Although the rotary engine can produce an impressive amount of power, it can also produce an impressive amount of exhaust noise! As exhaust noise level restrictions have become more common, sound level moderation for many rotary engine vehicle owners have become of greater concern. Through the use of carefully selected rotary-specfic exhaust components it is possible to install a system that offers performance increases, exhaust system longevity, and a modest sound level.
Early Rotary Exhaust
Some of the biggest power gains that were uncovered for the early 1970-80's rotary engine applications were from the removal and replacement of the stock exhaust components. But, adding restrictive presilencers and mufflers back into the system would only negate these new-found performance gains. Early attempts to use components that were originally designed for use on reciprocating engines, quickly failed on the rotary application due to the extreme heat produced by this engine.
Exhaust Material Selection
We have found that the use of a heavy-walled tubing material offers superior noise reduction qualities - but at the cost of added weight. We strongly advise against the installation of fiberglass filled mufflers as repeated exposure to a rotary engine’s hot exhaust gases will melt the fiberglass packing quickly, increase exhaust noise substantially, and cause you frequent replacement headaches. Uncovering the specifc material that is being used inside an aftermarket exhaust component can be difficult as many manufacturers do not publish or disclose this information. All Racing Beat exhaust components utilize the same basic internal design. Our mufflers and presilencers typically feature a design that incorporates a perforated stainless steel tube, which is then wrapped with stainless steel wool mesh (fine), and the canisters are filled with either high temperature ceramic wool or stainless steel wool (coarse). Since most automotive ceramic wool packing materials are designed for the temperatures of reciprocating engines, locating packing material that was suitible for use in a rotary engine application was a bit of challenge - but we found it!
The use of a presilencer unit in the exhaust system will aid the main muffler with sound suppression. Presilencer units, typically smaller in size than a muffler, are intended to be placed under the mid-section of the car and work together with the rear muffler to moderate the exhaust note. Over the years we've introduced a wide variety of both in-line bolt on presilencers and custom-fit universal presilencers to allow fitting and placement on a wide variety of applications. The exact components you select will depend on your engine configuration, power requirements, and specific driving application. Remember when designing an exhaust system for your specific application, the greater the length of a straight-through presilencer or muffler the greater the sound deadening effect. Short, simple presilencers and mufflers may look sleek and stylish, but simply can't off the same level of sound suppression as a longer unit.
On a RX-7, or comparible application, presilencer units are commonly placed after a header or catalytic replacement pipe (down pipe), and mate to the stock connecting pipe or Y-pipe (1986-92 RX-7). For use on a 1984-88 13B 6-Port engine application, the Racing Beat presilencer units include an exhaust backpressure pickup tube that will allow for the correct operation of the auxiliary intake ports on the engine. Without this critical feature, your intake will not operate correctly (the high power ports will not open) and a noticeable loss of high end power will result. If a muffler is used with headers only - with no presilencer(s) - the resulting exhaust sound level will be very loud and harsh, which may result in unwanted enforcement issues with local law enforcement. Therefore, presilencer is always recommended as an integral part of any high performance exhaust system.
The Racing Beat Power Pulse™ Presilencers (bolt-on) we manufacture allow a substantial reduction in high frequency and metallic noise, with no reduction in power. This presilencer can be installed in virtually any exhaust system configuration that uses headers. If you are using a long primary dual pipe system (the primary tubes run the length of the chassis and collect before the muffler), two presilencers will be required, one in each tube.
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