Apply to 90 size helicopters, according to the strength character of 90 engine to design, features much increase the horsepower, fuel-saving, low noise, and the highest air exhaust volume on the market.
?Great design and test to three spaces: expansion chamber, accelerated section, silencer chamber, high efficiency and the quick respond of medium speed and high speed, great for 3D flying.
?Use for O.S 91SR/HZ & ALIGN 91H/HP engine.