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Continued from page 7. When the egine is running without the cowling at 100 mph + there is a negative pressure at the carb venturi. It needs to see the same negitive pressure under the cowl. Various attemps to fly with some sort of fresh air ( read ram) to the cowl, did NOT work in varrying degrees of failure. What I have aranged now is the airscoop on the bottom is basically a venturi that sucks all the air out of the cowling. It remains to be seen how it will pan out when I put the bullets on the sides of the cowl. My guess it will be just fine and they will be there just for looks as the air rushing past will get sucked out the bottom as well. All results will be posted as they become available. |
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October 13 Well heres a news flash. Disregard the previous post about negative pressure. Seems I had been chassing a full throttle problem at the wrong end. While the air pressure was capable of effecting the running on the top end it was NOT the problem. After lots a R&D it was traced back to the fuel pumps. Seems there is a small screen inside the exit (or presure) chamber that covers a port for a over pressure relief valve. It would dump excessive pressure back to the intake side of the pump. This small screen twice got fine garbage packed into it and was my full power problem. Interestingly it was only one pump and the same one 2 times. So now I have gasolator (see pic of final fuel system configuration) that filters all gas. It is nice to know thought that the plane will fly with just one pump working normaly. Infact after fixxing this problem it statred to run rough in the midrange. That was traced to NO pressure in the cowl. Now that I have repressurized the cowl I have it all under control. It runs great across the rpm range and I am having loads of fun. Will post anything new. |
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3/7/07 Its been awhile sisnce I have posted, mainly because I have been enjoying the fruits of my labor and having fun flying. I did a X-Country flight to Copperstate it was a 660 mile round trip. And while I did experience a spark plug wire breaking down occasionaly it really was unerving more than anything. But it did help me to realize that the spark plugs must be in good condition (Champion D-6) as well as the wires. No further problems now. I did add a fuel pressure regulator with a fuel gauge but dont think its nesessary. More for R&D. I am going to work on a new spark plug. I have been using D-16s right now and it doesnt seem to make any difference other than it doesnt load up at all and uses less prime to start in the morning. I have since also done a lot of airframe cleanup and work and the performance numbers are stagering for this plane. I only used 4.6 gph on the X-Country flight and averaged 110 miles an hour. But that was with 17 gal of fuel a sleeping bag a tent a dig cam a pair of binoculars a back pack with all my clothes 5 bottles of oil (2400cc) 2 bottles of water, some food headset radio and gps. My guess I was grossing over 600lbs on takeoff. And it didnt even change the climb one bit. Cruise definetly suffered and it landed a lot easier. Stuck real well. So next post will probably be an update on new plugs. Going to try and get a fine wire tungnsten or something similar to the factory plug but in a motorcycle version (read cheaper) will inform when I am done with that. Until then look for the article to appear slated for May in EAAs Sport Pilot. |
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