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Rotax 618 piston scoring

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Rattler1 1

Well-Known Member
Joined
Dec 29, 2019
Messages
60
Location
USA
I've heard a lot of negative comments on the 618 scoring pistons and RAVE valve issues. (sticking) . I purchased a Sport Copter with a new rebuilt 618. The RAVE valve is supposed to open at 6200 RPM to give it more airflow out the exhaust at high RPM and close below 6200 for higher compression for better low end torque. My theory is that if the RAVE valve sticks closed the compression gets too high above 6200 RPM causing pistons to score. Especially when in lean conditions. I adjusted the prop on my Sport Copter for a high idle of 6500 RPM. Test flew it and could on.y reach a true ground speed of around 50 MPH. I then took and installed washers to hold the RAVE valves full open all the time. I test flew it and the high RPM went to about 6900. I actually increased HP at high RPM. I re-pitched the prop to achieve 6500 rpm and now have a true ground speed of about 70 MPH. I don't like to run it wide open but prefer to run about 6000 at cruise. I filled the fuel tank and marked the level. I then flew it for exactly 1/2 hour at 6000 rpm (60 MPH). I measured the fuel I then added to bring the level to the exact mark and it burned exactly 2 1/2 gal. That's 5 gal per hour.

Does anyone have any input on what I did here. I like the outcome and plan to keep it this way. I have been concerned about those RAVE valves sticking. I figure I only lost low end torque and ensured full HP at high RPM. I don't need the low end torque in an aircraft like you do in a snowmobile.

All comments welcome.
 
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