Ed Cesnalis Posted September 20, 2013 Report Share Posted September 20, 2013 Here at Mammoth there have always been crashes on departure due to the small piston single engine plane departing full rich. If you are behind a Lycoming or Continental and try to take off full rich, you will have degraded performance and rough running. The lyc and cont need to be leaned at WOT in order to keep from fowling plugs while you taxi and in order to provide adequate power to climb and take off. The Rotax can do what they can't it can operate full rich and not run rough. I don't know if it loses power or not because I cannot adjust the mixture. With the lyc and cont at a full power run up we would lean until we found max RPM and then richen 2 twists from there and that way determine best power for takeoff. With a 912 there is no equivalent leaning, both carbed and FI have no leaning at WOT. First I was curious as to why Rotax would not provide high altitude WOT leaning but now I realize there is first the question of why they can get away with it when it would mean departure crashes with other engines. Curious, would it be the high compression ratio making the difference? Link to comment Share on other sites More sharing options...
Jim Posted September 20, 2013 Report Share Posted September 20, 2013 The Bing carbs automagically lean the mixture at altitude. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted September 20, 2013 Author Report Share Posted September 20, 2013 The bings lean when the needle jet has control. Both FI and carbed models are not leaned at WOT which is used for take off and climb. Link to comment Share on other sites More sharing options...
Jim Posted September 20, 2013 Report Share Posted September 20, 2013 First time I've heard that. Link to comment Share on other sites More sharing options...
Doug G. Posted September 20, 2013 Report Share Posted September 20, 2013 How's that work CT? Is there a different circuit like the starting circuit in the carb? (This is the first I have heard of this also.) Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted September 20, 2013 Author Report Share Posted September 20, 2013 Idle is a distinct circuit then the needle jet gets control all the way until approaching WOT. Approaching wide open throttle the main jet takes control and the mixture is determined by the main jet. Most throttle positions give control to the needle circuit and the needle height is adjusted by the diaphragm that it sits on. The diaphragm is at the pressure differential and adjusts mixture according to the differential. Link to comment Share on other sites More sharing options...
CT2kflyer Posted September 21, 2013 Report Share Posted September 21, 2013 Frankly, I don't know why the Bing Carbs work as well as they do, but I routinely take off at full gross with a density altitude of 8500' on a hot day. KLMO has a geographic altitude of 5050', and on a 90-95 degree day, the plane will still levitate. The CT2k is an amazing aircraft. Link to comment Share on other sites More sharing options...
Roger Lee Posted September 21, 2013 Report Share Posted September 21, 2013 Hi Ed, They still lean because of the differential pressure in the dome part of the carb compared to the throat of the carb. This happens whether you're in mid-range or WOT. Variable throat carb. This engine is comparing apples to oranges to a Cont. or Lycoming and the FI engine can still make adjustments for altitude at WOT as well. If the carbs were of a standard type like other engines you would have an issue, but they do compensate. I have an ATV quad with a Rotax and it has a bing compensating carb and it works very well compared to my friends that have a standard carb when we climb up to 10K-12K'. If you idle for a while at your high elevation and then check the plugs you will have more black sooty plugs than us low landers. Link to comment Share on other sites More sharing options...
Doug G. Posted September 21, 2013 Report Share Posted September 21, 2013 Thanks CT, I guess I need to look over the carb info again. Link to comment Share on other sites More sharing options...
FastEddieB Posted September 21, 2013 Report Share Posted September 21, 2013 Tough going, but worth reading - perhaps more than once: http://avsport.org/docs/bing64.pdf Link to comment Share on other sites More sharing options...
Doug G. Posted September 21, 2013 Report Share Posted September 21, 2013 Difficult maybe, but at least it is not constantly depressing. (Sorry. ) Link to comment Share on other sites More sharing options...
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