flyrotary@lancaironline.net Mailing List Archive

My guess is that it is not excess pressure that is the problem. (we all wish we had more MP available : ). One possibility is turbulence around the mouth of the carb, had that happen on hod rods in my younger days. I turned the air scoop on carb around backwards and problem went away. You running an air cleaner or other intake plumbing that helps smooth the airflow at the entry of carb? Better yet, go EFI which isn't sensitive this problem! Tracy Sent from my iPad On Jul 9, 2012, at 10:36 AM, "Richard Sohn" <res12@fairpoint.net> wrote: > > > -----Original Message----- From: Ernest Christley > Sent: Monday, July 09, 2012 11:12 AM > To: Rotary motors in aircraft > Subject: [FlyRotary] Re: First lift off with single rotor > > Richard Sohn wrote: >> Cleared the ground for a brief period today. As far as the airplane is >> concerned, everything is good. CG seems to be right on the spot. Much >> better as it was 12 years ago at the first flight with the SOOB. >> Here is the reason why it was not a flight. A few days ago when I >> started high speed taxi, as soon as it picked up air speed, the engine >> started to sputter and almost cut out totally. This was at the same RPM >> as at a run up, where it does not do that. With a wiggly tail dragger as >> the Avid is, there was no way reading enough instrument for making a >> preliminary analysis. I recorded the instrument panel with a GoPro at >> 2sec intervals. >> Looking at the first pictures, the answer came up right away, increasing >> pressure under the cowl where the intake for the engine is located. Like >> the EGT shot up over 1600 just before the sputtering started. Since my >> radiator air is going to the outside of the cowling, there was no impact >> on cooling. Btw cooling is really good. At an OAT of 95F, oil and water >> stayed at around 170F no matter what I did. >> >> For todays runs, I taped the inlet around the prop hub shut. Sure >> enough, the sputtering occurred at higher airspeed, and was not as >> total, however, EGT was still going to around 1600. >> >> The conclusion is, I have to open the cowling exits a lot. > > I don't get it. The pressure under the cowl sounds like it would be a good thing, because it sounds like it is enough > to cause the engine to lean out. If the cooling isn't a problem, why wouldn't you just enrichen the mixture to > accommodate the extra air and accept the increase in power? > > Ernest, > > I am not using electronic fuel injection. My fuel system operates pretty much like a carb with mixture control. In addition, I would not want to have to adjust the mixture when changing the air speed. > Your comment certainly reflects one advantage of EFI. > > > Richard Sohn > N2071U > > http://www.fairpoint.net/~res12/home.html > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html