J L M Posted July 9, 2011 Report Share Posted July 9, 2011 Roger, after a few days of not flying, when I "burp" the engine it feels like not all cylinders have compression. It doesn't feel that way later in the day. There seems to be no performance problems, rpm's look normal, nothing acts wrong. Is this normal? Newbie here and not sure what I'm looking at. tks. BTW, tks for the info about the auto pilot, you were correct! Link to comment Share on other sites More sharing options...
Roger Lee Posted July 9, 2011 Report Share Posted July 9, 2011 Hi Jlm, What you are feeling is normal and is usually intermittent. Don't worry about it and go have fun. Link to comment Share on other sites More sharing options...
J L M Posted July 9, 2011 Author Report Share Posted July 9, 2011 Tks, I feel better now ! I'm at 19 hours on my training, and loving it ! Link to comment Share on other sites More sharing options...
airhound Posted September 22, 2012 Report Share Posted September 22, 2012 Roger, The book gives a range of 80-87, I think, so what are good numbers and what numbers give cause to be concerned?? Thanks Doug Link to comment Share on other sites More sharing options...
airhound Posted October 5, 2012 Report Share Posted October 5, 2012 Hi Jlm, What you are feeling is normal and is usually intermittent. Don't worry about it and go have fun. Roger, is 80 on a dif comp check the highest number obtainable...? Link to comment Share on other sites More sharing options...
Roger Lee Posted October 6, 2012 Report Share Posted October 6, 2012 When doing the differential compression test Rotax says to use any test pressure between 80-87 psi. It used to be only 87 in past years. Usually if you use 87 as a test pressure the normal residual is 83-85. If you use 80 test pressure then 76-78. I have seen some A&P's list the test as 80/80 or 87/87 psi. This can't be as the system is not air tight and air should be leaking out the oil tank and that is why you have a differential. He needs to have his gauges checked. No matter what the test pressure if you loose more than about 8 psi something is really wrong. The Rotax is so tight that just doesn't happen unless something is going on. Loosing the proverbial 25% would be a disaster. These aren't Continental's or Lycoming's. Think of it as more like a motorcycle engine and you'll be ahead of many A&P's. Link to comment Share on other sites More sharing options...
Doug G. Posted October 6, 2012 Report Share Posted October 6, 2012 Jim, one thing I was not told when I was new to this machine (not that long ago) is that when you burp the engine, don't just continuously crank on the prop, stop on the compression for a bit - the burp happens because of air leaking by the rings so give it a few seconds to do that. Link to comment Share on other sites More sharing options...
Tom Baker Posted October 6, 2012 Report Share Posted October 6, 2012 When doing the differential compression test Rotax says to use any test pressure between 80-87 psi. It used to be only 87 in past years. Usually if you use 87 as a test pressure the normal residual is 83-85. If you use 80 test pressure then 76-78. I have seen some A&P's list the test as 80/80 or 87/87 psi. This can't be as the system is not air tight and air should be leaking out the oil tank and that is why you have a differential. He needs to have his gauges checked. No matter what the test pressure if you loose more than about 8 psi something is really wrong. The Rotax is so tight that just doesn't happen unless something is going on. Loosing the proverbial 25% would be a disaster. These aren't Continental's or Lycoming's. Think of it as more like a motorcycle engine and you'll be ahead of many A&P's. Roger, the pressure differential is also a factor of volume of air being put in the cylinder. Link to comment Share on other sites More sharing options...
airhound Posted October 6, 2012 Report Share Posted October 6, 2012 Roger, the pressure differential is also a factor of volume of air being put in the cylinder. Thanks, which tester do you recommend? and which testor (Aircraft Spruce) for carb sync to you recommend...?? Link to comment Share on other sites More sharing options...
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