The thing about A/C engines,the exhaust is not always made for best performance,a lot has to do how to make it fit in a small enclosed engine cowling/s,some,engines have just straight pipe,not optimal always.
Most engines turn low RPM & therefore I think most typicle engine exhausts are designed for peak torque .
At least thats my take on them,they (the exhaust systems) do not look very well designed. I have been working on planes since 1988 & most look like crap,especialy the lower cost airplanes ,which would be 30,000-70,000 range & very old I might add.
MBHD
