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Tuned Exhaust: How it Impacts your Aircraft Engine

A tuned exhaust system is an option for some aircraft piston engines. Installation of a tuned exhaust engine can result in increased engine efficiency, increased power, and better performance. To better understand how it works and differs from a traditional engine, we need to know how a traditional engine works.

Your engine goes through four “strokes” during the combustion process. The Intake, Compression, Combustion, and Exhaust strokes. An “intake” valve is located at the top of the cylinder. During the intake stroke, the piston moves down the cylinder, sucking a new fuel/air mixture through the open intake valve. The intake valve closes, and the piston moves back up the cylinder, compressing the fuel air mixture, at which point a spark from the spark plug ignites and explodes the compressed mixture. This explosion forces the piston back down the cylinder, producing the necessary power to turn your prop. Next, the exhaust valve opens as the piston pushes out most of the spent fuel air mixture, and the cycle starts all over.

As the spent fuel air mixture leaves the cylinder, it is routed through a set of headers, into a common collector area, and pushed out the tail pipe by the remaining pressure. Like a garden hose with a kink in it, pressure builds up through out the exhaust system, making it more difficult for the spent gas mixture from the next cycle to leave. So now, the exhaust isn’t flowing as freely as it should, leaving some exhaust in the cylinder, taking up space better used for a clean fuel/air charge.

General manager Darren Tilman, an A&P and test pilot for Power Flow Systems said ‚ÄúTraditionally, the exhaust system on an engine was purely functional. It removed gases from the cylinder and got them out of the nacelle. Then the FAA came along and said ‘we need to muffle it’ and so they got rudimentary exhaust systems. And then you got pilots that didn’t like to freeze, so the manufacturers had to come up with a heating system. So they wrapped a piece of metal around the other metal and came up with a heating system. But everything was sort of a band-aid approach. It was an afterthought.”

The traditional exhaust engine has worked fine for years. There is always room for improvement, which is where the Tuned Exhaust comes into play. The main goal of the tuned exhaust is to more efficiently evacuate the exhaust gases from the cylinders. With a tuned exhaust system, you are always suctioning out and emptying out the cylinder more effectively. So less gas is wasted to overcome the inertia. The engine gets a more complete fuel burn. The effect in the cockpit is that it will take less throttle to get the same rpm than you are used to. This means less fuel flow. The EGT ends up going up a little bit because more of the exhaust gases are being emptied from the cylinder. But overall a tuned exhaust will help save fuel, promote a smoother, cooler, and finally more powerful running engine.

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