Martin Harris - Moderator Posted March 1 Share Posted March 1 Didn't you get it running much better earlier? "Only way it would fire up is main needle 2 turns out and l the low needle backing out to 9.5 turns out. Tick over is now decent and revs are in the 8 k.. I feel I can get more RPMS but it'll wait until tomorrow.. " Have you departed a long way from these settings for some reason? If it runs well at these, it should only need fine tuning from there... Forget any numbers of turns that you may have been quoted - as Jon has pointed out, all engines differ and the "correct" setting is where it runs best. Returning it may be an unnecessary effort - why not pop the more suitable prop back on, go back to those settings and post a video of you tuning it? 1 Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted March 1 Author Share Posted March 1 Hi Dennis.. it's back with MMM .. Will post again when I get it back.. Quote Link to comment Share on other sites More sharing options...
Jon H Posted March 1 Share Posted March 1 18x8 should be very acceptable for a 30cc class 4 stroke. I recommend 18x8 for our 180/200 as more or less the standard prop and i would expect 7500-8000rpm ish depending on the engine and the brand of prop. Aerostar props run fairly fast, so i would be expecting near the top of that rpm range for our engine. Saito always seem to want their engines to rev like mad while spinning a tooth pick. Not sure why. The little saito 45 i have in my Nieuport is turning a 15 inch prop at 6400rpm flat out and i have no bother with it at all...as long as i do not use full throttle for more than about 10 seconds as it then it gets a bit annoyed with me as the temperature rises. As i never need to fly it flat out its simply not a problem. The saito 170r3 i recently worked on recommends a maximum prop size of 16x8 using 15% nitro fuel, but i ran it very happily on a 17x8 using 5%. In fact i wouldnt dream of running it on anything smaller or using more nitro. It ran fine, and even better once i tweaked it. In any case the manual says a 15x8 will run 9400rpm, which works out to 2.4hp calculated. My 17x8 effort ran at 7800rpm or 2.28hp calculated so the engine is still quite comfy in its torque band. Thrust was up by about 2lbs, max pitch speed down a bit, but the thrust increase likely negates this. Propeller tip speed was down by nearly 12m/s so tip noise would be reduced as well. In this instance, there is no disadvantage to the big prop. Incidentally, you can often run larger props with low nitro than you can high as lower nitro fuel slightly reduces compression ratio due to the leaner (number of turns not actual mixture) running of the engine and less incompressible liquid in the cylinder. The petrol radial here will be more tolerant of a big prop as the ignition will not advance with the increase in head temperature like it would in a glow engine. Personally, i would expect to see 7500-8000rpm on an 18x8 and went looking for rpm numbers on these engines as your 6500rpm target seemed low. Reading reports online of 18x6's on these engines running in the 8400-8800 range, then subtracting the 500rpm/inch broad estimate of increased load from the 18x8 vs 18x6, we end up at 7400-7800rpm which is in line with my own prediction. If you are only seeing 5000rpm on an 18x8 there is either a substantial mixture problem, or you are missing a cylinder. If its only running on 2 that would explain the big loss of power. In your earlier video it was running on 3, but you may have an intermittent fault on a spark plug or something causing a cylinder drop out. Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted March 1 Author Share Posted March 1 Thanks Jon for your insight. It's been a unwanted trial for me. In the end I just wanted to get it back to mmm. I ended up doubting myself. It reminds me of a brand new ngh 30 FS. It went on the test bench for breaking in it wouldn't perform on the rpm following break in . Sent it back to Just Engines . After a few weeks they said no matter what they did ( checked ignition, changed carb) it didn't run.. ended up sending me a replacement unit.. They did say that i wasn't the only one that had this problem.. Cheers everyone. 1 Quote Link to comment Share on other sites More sharing options...
Jon H Posted March 1 Share Posted March 1 You do sometimes get engines that just dont work for some reason. I had a saito 180 that never ran as fast as the other one i had and behaved more like a 150. When you run as many engines as i do the differences between them become very stark, even when they have identical theoretical performance. I have test run batches of engines here where some run as expected, but others are just more 'alive' than their mates, while others seem flat and dead by comparison. They all do the same rpm at the top end, idle well etc and so all pass their test run. Its just they have different characters for some reason. I am probably the only person that would actually be able to tell the difference, but to me its very apparent. In the case of the NGH, i wonder if the cam was incorrectly installed due to the timing mark itself being in the wrong place. Had this on an enya 53 that a friend asked me to run in. It just didnt perform, so i checked the timing and saw it was wrong. The timing marks were correctly put together, but the angle of the cam was wrong. I spotted it right away as the enya and laser cam timing/cam profile are extremely similar and it just looked wrong. I compared it to my own 53 and this confirmed my suspicion. Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted March 1 Author Share Posted March 1 This is where the expert eye comes in. Master and the apprentice type thing. I'm definitely not expert, still making the tea ☕.. I'll keep you all posted. Quote Link to comment Share on other sites More sharing options...
ARC Posted March 11 Share Posted March 11 Hi Derek i have the 33r3 and had issues with it running , opted for the upgrade from MMM(new inlet) and the collector ring . its been great ever since no probs 1 Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted March 11 Author Share Posted March 11 1 hour ago, ARC said: Hi Derek i have the 33r3 and had issues with it running , opted for the upgrade from MMM(new inlet) and the collector ring . its been great ever since no probs Hi ARC It has all his mods,, I'm waiting for him to get back to me with some good news. Quote Link to comment Share on other sites More sharing options...
ARC Posted March 14 Share Posted March 14 On 11/03/2024 at 14:40, Derek Broadhurst said: Hi ARC It has all his mods,, I'm waiting for him to get back to me with some good news. Fingers crossed its gets sorted for you , mine is currently in a seagull neiuport 28 the sound is spot on and needs the nose weight so a win win all round Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted March 14 Author Share Posted March 14 7 hours ago, ARC said: Fingers crossed its gets sorted for you , mine is currently in a seagull neiuport 28 the sound is spot on and needs the nose weight so a win win all round Nice to hear that ARC . I'm hoping to post good news soon.. thanks again for everyone's input. Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted April 22 Author Share Posted April 22 Hi everyone I have finally been given some good news from MMM. He's had the engine back on the bench, serviced it and re tuned it . It's now reading 6700 RPM. Starting easily good tick over... Looking forward to getting it back and on my test stand.. Many thanks for all the interest in my problems and help offered... 3 Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted Sunday at 20:19 Author Share Posted Sunday at 20:19 On 22/04/2024 at 13:39, Derek Broadhurst said: Hi everyone I have finally been given some good news from MMM. He's had the engine back on the bench, serviced it and re tuned it . It's now reading 6700 RPM. Starting easily good tick over... Looking forward to getting it back and on my test stand.. Many thanks for all the interest in my problems and help offered... Hi ... After receiving the engine back I have remounted it on my test bench. Mixed up a fresh mix of oil and fuel 20/1 18/6 wood prop... idles at 1300..peak RPM 6450.. it's smooth and sounds excellent... MMM used a 17/6 prop.. hence 6700 . I'm so happy to finally have a good conclusion.. Now to get it in a airframe... Thanks for the help and advice with this matter. 2 Quote Link to comment Share on other sites More sharing options...
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