Engine Conversions Discuss all aspects of engine conversions in this forum


Old 02-07-2023, 12:30 PM
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Hello fellow flyers.
I ll fairy new to rc flying. Been flying for about 1.5 years now. In the beginning I flew mostly electric. Than glow. Still have 2st and 5st glow.
I have just been flying with dle20. Seems okay but throttle transition is not all equal. Also have os ggt10 and ggt15.
Ggt15 is good motor. Not at all sensitive with nidles. Tick over is bit hight but you can always convert to spark
Ggt10 is headache. It runs and next time doesn't. Looses power. Just as you taking off it looses power and stall.
I have saito 100 and I am working in on to convert to gas as its a glow guzzler. And mess. Once go gas you never go back!
Old 02-07-2023, 01:55 PM
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HI Sokat,

The "loosing power in take off" as you experience with your GGT10 is most likely a matter of an ever so slightly lean setting of the HS needle. The mechanism behind this, is in the fact that the engine unloads a bit linear to the plane picking up speed. This causes a slightly higher RPM, which means it also takes in a bit more air. Now if the fuel flow follows that increase in air exactly proportionally there is no problem. But not all carburettors are flawless, and some have a distinct tendency to have this fuel flow lag behind a bit, resulting in a leaner fuel/air ratio in take off, compared to that of a static full throttle condition. The limits between "just right" and "borderline too lean" are WAY MORE narrow for gasoline compared to Methanol, one of the reasons why for many decades Methanol was the fuel of choice.

As for the conversion of your Saito:
Mind you, the OS engines you have are designed to run pretty lean fuel/oil ratio's, and the Saito being designed as a glow engine, will require a fuel/oil ratio that will damage your OS engines. The OS engines due to their roller bearing conrod require a ratio of 40:1 (from memory, please refer to your manual), the Saito's require a ratio "fatter than 20:1", which basically means somewhere in the region of 15:1. Anything 20:1 or fatter endangers the roller bearings used in the OS engines, therefore please be aware that you need separate mixes.

Having said that, if carburation is adapted, the Saito's run really well on gas, I have converted a few. You can look at my YT channel "rigididiot" to see a few in various sizes.
Just for starters, keep in mind that your Saito in original state does not have a thermal barrier between the header and the carburettor, and this is an absolute necessity for a succesful gasoline conversion. They can be fairly easy improvised with a PTFE, plywood or heavy gauge gasket washer between header and carb (if appliccable, also thermally isolate any attachment point between engine block and carburettor, ANY heat transfer from engine to carb is detrimental).

Feel free to ask any additional questions, anytime.

Last edited by 1967brutus; 02-07-2023 at 11:18 PM. Reason: Additional information.

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