Exhaust Information

For those who have been around when rotary engines were first introduced, you would probably remember how annoying an unmuffled rotary sounded. Most drag-racing rotary enthusiasts were of the belief that rotary engines worked best without the restriction of a muffled exhaust system. Just like their piston engine counterparts.

Whether this was true or not, there was an underlying problem: ugly noise. For this reason, drag racing promoters got together and banned unmuffled rotary engines. So, the rotary exhaust system was born.


A number of specialist have taken the liberty of developing exhaust combos to suit both street and race applications. We, at Selectmaz are leaders in this area, having invested heavily in its development. We have come to the conclusion that no mass-produced exhaust setup properly caters for a high-performance street rotary.

Our workshop and development manager Issy Sveticic has this to say: "While most of the talk among rotary friends tends to revolve around bridge versus peripheral ports and carbon vs. ceramic apex seals, the humble exhaust is usually forgotten.

"The exhaust system attached to a rotary engine is probably the single most important factor in unleashing its power potential…."


For all street systems it’s necessary to keep exhaust sizes below 2.5 inches in diameter to minimize boon and resonance. In most Australian states it’s nearly impossible to drive any car on the roads with sound at more than 95dB(A).  We have made and catered twin tuned exhaust systems to suit Mazda vehicles, these systems run heavy gauge Extractors with thick laser cut flanges for a precious fit. From there they travel individually into handmade 4" Resonators before finally joining into a collector over the diff into our custom Handmade Muffler, We make these mufflers with heavy gauge steel and stainless steel packaging before it exits into two custom made stainless steel tips,  these components offer superior sound and performance and will outlast any other muffler in the Market.


The importantance of turbo systems is that they must sound quite yet flow enough exhaust to make horsepower.  The other problem is that turbos with internal waste gates also relies on backpressure to help keep the boost stable and not spike to uncontrollable levels.  We offer both bolt on systems and custom systems to suit your vehicle. With the twin system mentioned in the street package and a 3" dump pipe from the turbo split into the system, we have found that not only does it flow good, but has a sound that can only be heard to be believed. When driving in cruise conditions the exhaust is almost undetectable but when you power on it omits a muffled yet unrestricted note that wont drone or deafen you.  The bolt on systems are 80% bolt on with the dump pipe made custom to suit your turbo position and vehicle.  We also do complete 3" systems for drag or racing vehicles using high quality mandrel bent tubes.  Our Fabrication department can also custom make you a Exhaust Manifold to suit a wide range of turbos in either internal or external Waste gate setups, these have the option of Stainless steel or steel bends.  But for the most common Mazda turbo conversation we offer cast exhaust manifolds to suit.


For circuit racing there is also a noise limit, higher than the street limit but still a limit that must be adhered to. In this application, the primary system lengths - 2-inch tube into stainless steel packed resonators before joining into a single 3-inch pipe before exiting the car via a Selectmaz race muffler. With this system the Selectmaz 13B race bridge port has given us incredible results on our Dyno Dynamics Dyno and truly give us the performance our Race engine can offer


Be very wary of low quality systems; they may save you a few bucks in the short term but they’ll cost a lot more later on. Remember that to complete the package and maximize the result it is essential that the jetting and ignition settings be re-optimized to suit by people who fully understand rotaries.