Jim Burton 1 Posted October 24, 2011 Share Posted October 24, 2011 TT say the rev range for this (new, unflown, but broke-in) engine should be 2.2k rpm to 13k rpm. I've measured the revs using the break-in size prop 11x5 and also a scale 12 incher: apart from the big prop running a tad slower, there is little discernable difference at the low end - the motor coughs and dies below 4.5k rpm. And flat out is a bare 10k with either. Understandably, I'm not going to fly the plane like that Using the 'pinch test' as a guide, I'm set at 3 turns out on the mix needle. I'm using the glow plug TT provided with the engine - the recommended TT Redline RF 9776. The fuel recommended by TT is "20% oil mix and 10-15% nitro". The guys at Model Technics fell about when I showed them this and said their ubiquitous Contest 10 would be just fine. I wonder... Word on the field, as guys formed a line to my test bench, was 'get a hotter plug' and the hotter plug most often mentioned was Enya no3. Most model sites describe Enya 3 as a 'standard' heat, however Enya engines.com themselves call it HOT. http://www.enya-engine.com/plug_E.html I've ordered one anyhow. D'you reckon this will do the trick, or is a better route to stay with the TT plug and source a 20% oil blend fuel?Edited By Jim Burton 1 on 24/10/2011 19:39:34 Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted October 24, 2011 Share Posted October 24, 2011 hello jim...reading your post... i dont think your carb is set up correctly...i would hazard a 99% certain guess and say it is open too much at the top end and probably too much at the bottom end ..... and the plug cant cope with the excess fuel at the slow end.....you should be ok with fuel with 5/10% nitro in it..... i would check out the carb and dont worry too much about the fuel or the plug type....dont forget if you alter the bottom needle then the top one will need altering also.... ken anderson ne..1.. 4st dept. Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted October 24, 2011 Share Posted October 24, 2011 The plug you are using is fine, keep the glow driver attached and then reduce throttle if engine keeps running a lot lower than without then engine too rich bottom end Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted October 24, 2011 Share Posted October 24, 2011 Firstly Jim explain the pinch test,3 turns out seems high,have you tried the pin and blow down fuel tube as described by Brian Wich to set tickover mix? Quote Link to comment Share on other sites More sharing options...
stuey Posted October 25, 2011 Share Posted October 25, 2011 From what I have learned re 4 strokes recently, I wouldn't expect anything near 13000rpm on a prop you would want to fly with. A 12x6 on a good 52 would probably top out at around 10000 anyway I would say. An idle around 2500rpm shoule be ok once its fully run in. Does sound like a rich carb issue as said above. Three turns out also sounds a lot compared to other engines, I would think between 1 1/4 and 2 turns out may be more normal. I would concentrate on getting the top end needle set right first, before trying the bottom end. You will need to double check the top after doing the bottom end, and then hopefully be nearer the mark. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 25, 2011 Share Posted October 25, 2011 I'd put it stronger than that, Stuey - Jim MUST set the high end needle before attempting to adjust the idle mixture - these are very simple carburettors and the main needle affects settings throughout the range. Also, the engine needs to be thoroughly warmed up to operating temperature. I'd certainly agree with the figures you've given. Stephen, the pinch test is done at idle - the fuel tube is pinched to stop fuel flow and the result observed. If the engine dies immediately, the theory says it is lean, a quick blip and stop is about right and a sustained idle for several seconds means too rich. I favour leaning the idle screw for max rpm at tickover then checking the transition and making fine adjustments from there - cutting during transition meaning too lean and a burbling pick-up indicating too rich. It's worth fine tuning again by checking the top end setting after this and repeating the idle adjustment if any change was required. Any compromise necessary due to the design/manufacturing tolerances of the scroll (which controls the air/fuel mixture at intermediate settings) need to be to the rich side.Edited By Martin Harris on 25/10/2011 11:02:08 Quote Link to comment Share on other sites More sharing options...
Jim Burton 1 Posted October 25, 2011 Author Share Posted October 25, 2011 Thanks guys, I'll go back to the field bench and put your tips into practice. To sum up: a) fuel and plug OK; b)10k rpm tops is normal; c) 3 turns out is way too rich - aim for +-2 d) adjust (lean-in) WOT mix for max revs - less a couple of safety-richening clicks. e) when engine fully warm go to idle and adjust the low mix screw clockwise by 1/8th turn until a smooth safe idle is attained. Question - I'm guessing that my dream of a smoothly-purring 2.2k idle is not going to happen and so - what realistic idle revs should I be happy to fly with, to bring in to a safe landing a 3.3kg high wing trainer (Ready 2)? Quote Link to comment Share on other sites More sharing options...
stuey Posted October 25, 2011 Share Posted October 25, 2011 I guess the engine is mounter upright so you should not get any issues with 'loading up', I would say something around 2500-3000 rpm on a run in engine should be easily attainable and fine for landing. Each model has differing requirements for landing speed, so hard to say exactly. Also good if the model will idle without rolling along, the surface can make a difference there. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted October 25, 2011 Share Posted October 25, 2011 jim-dont forget-when you alter the bottom needle and get the motor ticking over nice'ly...you will need to alter the top end ...... ken anderson.... ne..1 top end dept Quote Link to comment Share on other sites More sharing options...
Jim Burton 1 Posted October 25, 2011 Author Share Posted October 25, 2011 Thanks Stuey - it's mounted sideways BTW - I've no idea what the 'loading up' effect you mention means. You might explain if you have time. Anyway, anything smooth and reliable sub3k rpm should be fine you reckon, so that's what I'll aim for. And Ken, I'm assuming that the bottom end will need leaning in my case, if we have read the symptoms aright, so that will affect the top mixture, er, how? Logic says the top end will become overlean if it is so adjusted at the bottom end, am I right in this assumption, i.e. that leaning the bottom will then involve counter-richening the top? Quote Link to comment Share on other sites More sharing options...
stuey Posted October 25, 2011 Share Posted October 25, 2011 Loading up as I understand it affects inverted installations more. It is when the engine struggles to ignite the mixture after idling for a while as it sits around the plug, leading to it cooling and the engine stopping. This can be caused by the tank being too high in relation to the needle valve (middle of the tank should ideally be in line with the main needle when looking from the side) or an over rich idle mixture. I think thats right!! Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted October 25, 2011 Share Posted October 25, 2011 jim--have a look at the carb--you'll see that one needle go'es into the other....so as one is altered-it effects the other......hence having to alter the top end after the bottom end.... ken anderson ne..1 top/bottom end dept. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted October 25, 2011 Share Posted October 25, 2011 I sometimes use the pinch to stop the engine when Idling to high.thought it was as described but not that it could read anything into it.The other thing is how new is the engine maybe run it in for a bit longer before altering the idle screw Quote Link to comment Share on other sites More sharing options...
Jim Burton 1 Posted October 25, 2011 Author Share Posted October 25, 2011 Yes Stephen, my thoughts exactly: I had been told by several modelers as well as the molecular chemists at Model Technics that 'fiddling' with the low end mix screw would likely be unecessary/inadvisable on such a modern engine, as it would have been optimised at the hi-tech factory. Therefore I've left it at the factory setting. It must have had 5 or 6 complete tanks of fuel: I certainly have the patience to give it another couple of tanks, if you think this would help it settle. And only then tweak the low-end adjuster. Ken, that's good advice. I can see now from the exploded view: how the two needles oppose each other in the barrel K, and how the main mix needle C reduces the size of the largest air intake hole, whereas the slow mix needle J does the same for the lesser sized hole. As they are both in the same chamber K, like you say, one will affect the other, so some 'juggling' will be required. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted October 25, 2011 Share Posted October 25, 2011 go on jim...... your getting there...what you will find is once the bottom end needle is set and the engine will sit there ticking over like a goodin...that will be it.......with only minor alteration's to the top end needle.......once your engine/prop is sorted-the only time you should need to alter the top end needle is if...you change the size of prop.... Or...... the type of fuel...or if there is a big change in the temps between flying session's..... ken anderson ne..1.....settings dept.... Quote Link to comment Share on other sites More sharing options...
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