stuartasutherland Posted June 21, 2011 Share Posted June 21, 2011 Hi, now I've been up a few times I can judge how much fuel I'm using. Generally using 3.5L for each 30 min flight. Just looking for comment on whether this is normal or is there something I can look at to get it improved. Parajet Macro - 2 blade wooded prop Dudek Synthesis 34 I weigh 100kg naked and a bit more with clothes on. I'm suffering a bit from vibration at the moment - could that reduce the fuel economy? (Prop balancing issues - details on my other post). Anyway, comments welcomed. Many thanks Stuart Quote Link to comment Share on other sites More sharing options...
aquatix Posted June 21, 2011 Share Posted June 21, 2011 No that's not normal - I get 3.5l per hour (or better) from a 230cc Kobra paramotor and 34m Nucleon. Similar weight to you or slightly heavier. Is your plug black & sooty ? Any idea what rpm your motor is at on a level cruise ? The parajet 3 blade carbon prop might help a little bit. Quote Link to comment Share on other sites More sharing options...
stuartasutherland Posted June 21, 2011 Author Share Posted June 21, 2011 Here is the plug after last nights flight - probably a bit sooty on the threads. Too rich? Quote Link to comment Share on other sites More sharing options...
aquatix Posted June 21, 2011 Share Posted June 21, 2011 That plug actually looks fine (from that angle), but really you need to judge it from the colour of the porcelain part way down from the electrode. Also that probably shows your idling mixture if you let it idle at all before switching off - you need to do a 'plug chop' after high revving under load for at least 2 minutes (preferably a steady climb above your landing field then kill the engine immediately before drifting down to land). There could be other reasons for the high fuel burn other than mixture, such as worn or stuck piston rings, worn or grooved cylinder bore, leaking or coked up exhaust to name a few. Do you know how many hours are on the engine ? Quote Link to comment Share on other sites More sharing options...
stuartasutherland Posted June 21, 2011 Author Share Posted June 21, 2011 150 - 200 hours I believe, with a rebuild just before I got it (done by Parajet), so should be okay inside. Hmm Quote Link to comment Share on other sites More sharing options...
Tom_McBride Posted June 21, 2011 Share Posted June 21, 2011 My macro has similar fuel economy seems to run OK so never worried about it, maybe I should have? Tom Quote Link to comment Share on other sites More sharing options...
aquatix Posted June 21, 2011 Share Posted June 21, 2011 Parajet & Corsair engines tend to be a bit thirstier than others but shouldn't use anywhere near that amount - especially as you are well inside the weight range on a 34 Synthesis. If it is rebuilt then maybe it is just the carb tuning ? Quote Link to comment Share on other sites More sharing options...
stuartasutherland Posted June 21, 2011 Author Share Posted June 21, 2011 I'll tune it up a bit leaner. Being new to this, I was a bit worried reading all about seized pistons when run too lean. See how I get on. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
aquatix Posted June 21, 2011 Share Posted June 21, 2011 Make a note of the current settings before you touch anything, and don't adjust more than 1/8th of a turn at a time, checking the plug colour after each flying session. http://www.rotaryeng.net/Spark-plugs/Spark-plugs.html Quote Link to comment Share on other sites More sharing options...
dugald Posted June 23, 2011 Share Posted June 23, 2011 The shorter prop you put on would also be a bit less efficient perhaps than the original. From what I gather, the bigger the prop, the more efficient it is. I would think that the vibration is definately wasting energy to some degree, but no idea if it is enough to make any difference to your fuel burn. My FB simonini states 3L/hr burn and I a getting around 4.5L/hr in practice, using a 29m non reflex wing with trims on all the time (no bar). Im 86kg. I think flying style makes a difference though and reckon I could get it down to 3.5 if I kept trims in, stayed lower and was lighter on the throttle. A larger more modern wing would also improve things quite a lot (mine is 12 years old!). I also heard that an iridium tipped plug improves efficiency, but doubt the difference is significant. Quote Link to comment Share on other sites More sharing options...
helimed01 Posted June 25, 2011 Share Posted June 25, 2011 In 2008 I had a brand new Macro for the tip to tip and spent a month testing fuel burn etc for flight planning. Looking in my flight log where i recorded some of the the fuel burn it reads: 6.25 ltrs hour 5.23 ltrs an hour 5.5 ltrs hour 5.31 ltrs hour. I weigh a bit more than you and was flying a medium size Action at the time. So i would say 5.5 to 6.5 is about normal. Technique does make a difference. Make sure the tank is the actual size you think it is. Some of the small Parajet tanks actually only hold 8.5 ltrs instead of 10 which we found out while testing. Some of the early clear tanks had thicker walls than the black tanks but were made in same size mould making the contents less. The large Macro tanks we used on tip to tip held 13.75 ltrs if you tilted them slightly to fill right up, and on the first test flight of the large tank which was on 23.06.2008 I flew 68.8 miles in 2 hours 31 mins before running out of fuel approaching my field as planned. The flight record described very lively conditions. Returning 5.5 ltrs hour. Be carefull you don't lean off and seize your engine. been there and done that Just spoke to Dan Burton who has swopped his Walbro carb for a Bing carb with pump, and is now getting 4Ltrs an hour instead of nearer 6 and sometimes was more on his revo 2 which in my opinion is to small for him. Regards. Quote Link to comment Share on other sites More sharing options...
helimed01 Posted June 25, 2011 Share Posted June 25, 2011 No that's not normal - I get 3.5l per hour (or better) from a 230cc Kobra paramotor and 34m Nucleon. Similar weight to you or slightly heavier.Is your plug black & sooty ? Any idea what rpm your motor is at on a level cruise ? The parajet 3 blade carbon prop might help a little bit. 3 blade props will burn more fuel for sure. Larger 2 blades is better for economy. You need to get it balanced as it will cause damage to your machine. Regards. Quote Link to comment Share on other sites More sharing options...
aquatix Posted June 26, 2011 Share Posted June 26, 2011 3 blade props will burn more fuel for sure. Larger 2 blades is better for economy. I find the opposite - the Helix 3 blade prop as supplied by Kobra for the Simonini Evo is quieter, more economical, efficient & powerful than the 2 blade glassfibre prop I bought as a spare (which is wider, greater pitch but a tiny bit shorter) although the 2 blade prop is a lot thicker which may effect its efficiency. Quote Link to comment Share on other sites More sharing options...
stuartasutherland Posted June 26, 2011 Author Share Posted June 26, 2011 Whitters, thanks a lot for that info - really helpful. I have one with the 14L tank (Simon's old one). I've marked the tank with lines after putting in exact amounts so should be an accurate measurement. As my technique gets better I'm sure I can improve down within the range 5.5 to 6.5 (with out leaning the engine!) My prop is currently with Pete B getting checked for balance. Appreciate your thoughts. Thanks Stuart Quote Link to comment Share on other sites More sharing options...
pete_b Posted June 26, 2011 Share Posted June 26, 2011 Whitters, thanks a lot for that info - really helpful. I have one with the 14L tank (Simon's old one). I've marked the tank with lines after putting in exact amounts so should be an accurate measurement.As my technique gets better I'm sure I can improve down within the range 5.5 to 6.5 (with out leaning the engine!) My prop is currently with Pete B getting checked for balance. Appreciate your thoughts. Thanks Stuart First one is done and tested on my motor it was 10 grams out in the cord (the weight of a pound coin) Second one now done will try to post tomorrow if I can get to the post office Pete Quote Link to comment Share on other sites More sharing options...
stuartasutherland Posted June 26, 2011 Author Share Posted June 26, 2011 I'm really glad there was an obvious issue. Thanks. Quote Link to comment Share on other sites More sharing options...
stuartasutherland Posted July 2, 2011 Author Share Posted July 2, 2011 Props are balanced but still slight vibration - perhaps normal. On the up side, a fantastic flight over Fife this morning. 1 hour 45 minutes @ 5.71 L/Hr average. Awesome. Quote Link to comment Share on other sites More sharing options...
norbertflyer Posted July 2, 2011 Share Posted July 2, 2011 My early afternoon flight of 2h14m cost me 3.5l today. I love thermalling! Richard Quote Link to comment Share on other sites More sharing options...
Tom_McBride Posted July 3, 2011 Share Posted July 3, 2011 12ltr's in an hour and a half and landed on fumes mate did same on his pap tank half full when he landed! Tom Quote Link to comment Share on other sites More sharing options...
stuartasutherland Posted July 3, 2011 Author Share Posted July 3, 2011 12ltr's in an hour and a half and landed on fumes mate did same on his pap tank half full when he landed! Tom That makes me feel better! I did 5.7 L/hr. Quote Link to comment Share on other sites More sharing options...
helimed01 Posted July 13, 2011 Share Posted July 13, 2011 12ltr's in an hour and a half and landed on fumes mate did same on his pap tank half full when he landed! Tom Perhaps its drag caused from Mustache and big grin when flying. Quote Link to comment Share on other sites More sharing options...
stuartasutherland Posted August 2, 2011 Author Share Posted August 2, 2011 In 2008 I had a brand new Macro for the tip to tip and spent a month testing fuel burn etc for flight planning. Looking in my flight log where i recorded some of the the fuel burn it reads:6.25 ltrs hour 5.23 ltrs an hour 5.5 ltrs hour 5.31 ltrs hour. I weigh a bit more than you and was flying a medium size Action at the time. So i would say 5.5 to 6.5 is about normal. Technique does make a difference. Make sure the tank is the actual size you think it is. Some of the small Parajet tanks actually only hold 8.5 ltrs instead of 10 which we found out while testing. Some of the early clear tanks had thicker walls than the black tanks but were made in same size mould making the contents less. The large Macro tanks we used on tip to tip held 13.75 ltrs if you tilted them slightly to fill right up, and on the first test flight of the large tank which was on 23.06.2008 I flew 68.8 miles in 2 hours 31 mins before running out of fuel approaching my field as planned. The flight record described very lively conditions. Returning 5.5 ltrs hour. Be carefull you don't lean off and seize your engine. been there and done that Just spoke to Dan Burton who has swopped his Walbro carb for a Bing carb with pump, and is now getting 4Ltrs an hour instead of nearer 6 and sometimes was more on his revo 2 which in my opinion is to small for him. Regards. My last few flights I've managed to average 6 litres / hour. This gives me a 2 hours duration plus a wee reserve. Quote Link to comment Share on other sites More sharing options...
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