Robin Stevens Posted September 14, 2019 Share Posted September 14, 2019 I am currently building a Toot Sweet (Peter Miller, RCM&E September 2002) and I'm thinking of putting a Petrol engine in the nose instead of the recommended glow. **LINK** This will be my first venture into Petrol, the relative cleanness and the cost and availability of fuel is attractive but I don't know what the best option for a plane of this size would be. I will admit that my knowledge on this type of engine is low, that's why I'm posting the thread. The plan suggests a 0.35 to 0.40 glow 2-stroke, or a 0.40 - 0.48 4-stroke. Does petrol suffer a performance penalty compared to glow or are they broadly equivalent, requiring a larger engine? Are petrol engines in this size available or should I just put a 9cc in and have almost unlimited performance? Currently the airframe is half built and is a winter project lined up. I would like to finish it for next year to give me something aerobatic to work with and flesh out the variety in my hangar. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 14, 2019 Share Posted September 14, 2019 I beieve that the smallest commecial petrol engines are around .60 which is rather big for Toot Sweet, However Just Engines can supply ingniytion systems to convert any engine to petrol. The job is not hard and might be a good option although you do have to fit about 4 ounces of extra equipment but that would apply to any ignition engine. Quote Link to comment Share on other sites More sharing options...
Robin Stevens Posted September 14, 2019 Author Share Posted September 14, 2019 Ok, thanks for the tip, I wasn't aware it was possible to do an engine conversion like that. I have an SC 0.40 two-stroke that was originally intended for the toot sweet that would be useful if I can convert. Quote Link to comment Share on other sites More sharing options...
J D 8 Posted September 14, 2019 Share Posted September 14, 2019 Converting small glow to petrol is never that simple, more so if you expect it to throttle well. Quote Link to comment Share on other sites More sharing options...
Robin Stevens Posted September 14, 2019 Author Share Posted September 14, 2019 I might be best to just stick with glow then, throttle response will be critical on an aerobatic model like the Toot Sweet. I'll think about it again when I'm closer to finishing the model. I don't expect there to be any massive improvements in the small engine offerings but it could happen. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 14, 2019 Share Posted September 14, 2019 I would definitely go with the .40 two stroke myself. I always work on the KISS principle and also the old saying "What isn't there can't go wrong" Quote Link to comment Share on other sites More sharing options...
Levanter Posted September 14, 2019 Share Posted September 14, 2019 I built a Toot Sweet a couple of years ago. Here it is with an OS 48 FS Surpass along with its little sister Yuppy Love. Fits in beautifully. Another view. Has not been flown yet Levanter Quote Link to comment Share on other sites More sharing options...
Robin Stevens Posted September 14, 2019 Author Share Posted September 14, 2019 Nice colour scheme, looking good liking the eyes on the side rather than a cockpit. Looks so fish-like it could be Guppy Love I take your point on KISS, was worth asking though just in case. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 15, 2019 Share Posted September 15, 2019 I believe the main problems with running small engines on petrol revolve around carburation and cooling. Glow carbs are extremely simple devices which work acceptably when metering the relatively large volumes of fuel used relative to petrol. As the metering involves tapered needles, you will probably find that the adjustment minimum of one click on the knurled body is too coarse to achieve an accurate mixture setting. Walbro type carbs work well in larger sized engines but aren't really suitable for anything smaller than a .60 - and maybe .90s upwards are better suited and getting something suitable for an engine conversion may involve a large amount of luck as there is so much variety and lack of info from the makers. Petrol engines also need more cooling as the fuel burns hotter and as the finning on a glow engine is designed to maintain the correct temperature range for methanol fuel, will be far less tolerant of any inadequacies in cooling air flow. I also have an inkling that vapour locking could contribute to problems due to the higher temperatures and higher vapour pressure of petrol vs methanol. Edited By Martin Harris on 15/09/2019 12:55:07 Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted September 15, 2019 Share Posted September 15, 2019 Robin, I think if Jon (Mr Laser engines) was contributing to this thread he would advise you against trying to convert a small glow engine to petrol for all the reasons Martin outlined above, plus a few more no doubt. Probably any quality 4st engine between 40 and 60 size will be much less bother, lighter and QUIETER than a small petrol two stroke. If it is cleanness and less cost you want why not go electric? Edited By Piers Bowlan on 15/09/2019 19:34:08 Quote Link to comment Share on other sites More sharing options...
Tim Flyer Posted September 15, 2019 Share Posted September 15, 2019 Martin explains it very well I think. Methanol is a wonderful fuel with a high latent heat of evaporation that helps draw heat from the engine. It also has a very high octane and resists pre ignition much better than petrol and allows us to use higher compression ratios and high rpm . It does require a much richer mix than petrol to burn but that is still an advantage as the fatter mixture extracts more heat . Petrol has a much higher heat or energy value than methanol ( about 10 times as much ) but it requires much more oxygen to burn so needs a far leaner mix . The difference between methanol and petrol mix, is that the petrol mixture requires around twice as much oxygen for a given amount of fuel. For smaller IC engines is very hard to beat glow for simplicity easy handing and performance. Edited By Tim Flyer on 15/09/2019 20:59:34 Edited By Tim Flyer on 15/09/2019 21:12:19 Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted September 15, 2019 Share Posted September 15, 2019 There is a NGH 09 engine... Surprised no-one mentioned that. Edited By Paul Marsh on 15/09/2019 22:00:51 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 15, 2019 Share Posted September 15, 2019 I thought the OP did! "or should I just put a 9cc in and have almost unlimited performance?" However, the thread has moved on to discussing conversions. Edited By Martin Harris on 16/09/2019 00:06:08 Quote Link to comment Share on other sites More sharing options...
cymaz Posted September 16, 2019 Share Posted September 16, 2019 I would put a glow in for that size. If you have a noise sensitive site getting a decent muffler on it would add a lot of weight. Four stroke glow would be my choice but if you’ve got your 2 t already bolt that in. Edited By cymaz on 16/09/2019 06:18:54 Quote Link to comment Share on other sites More sharing options...
barry saint Posted September 16, 2019 Share Posted September 16, 2019 Hi Have been flying a Toots sweet bipe for several years with a OS48 surpass,perfect combination will do rolling circles all day long & continuous vertical rolls,great little plane, Quote Link to comment Share on other sites More sharing options...
Robin Stevens Posted September 16, 2019 Author Share Posted September 16, 2019 Thanks for the recommendations I think I'm going to go with the SC 0.40 two stroke glow that I have from another aircraft that I'm retiring. Looking forward to having the toot sweet finished, everything I've heard about it makes me think it'll be a fun flyer. My club isn't fussy about noise, we're fortunate in being in the middle of nowhere. A trusty glow 2-stroke will likely give me all the power I could need and be relatively practical. Quote Link to comment Share on other sites More sharing options...
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