Thunder Tiger F 91S and OS FS 91S II design comparison

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This is the third comparison pair, now in 0,91 cubic inch class.
Both engines were new, from the box, so there was no any signs of fuel, residue or else imperfections.
There was very interesting to collect a lot of impressions about engines design, constructional details and build quality, comparing consequentially three pairs of O.S. FS engines and Thunder Tiger F engines in the same size and class.
Of course, there are still their launches ahead and their comparisons already in the real world, with real loads.
In the meantime - look, do not be served, and criticize if you do not like something.
And well, if you like it - don't be shy, put likes and subscribe to CrazyEngines!
Thanks and have a nice day !

Опубликовано:

29 сен 2024

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Комментарии : 15

@antoniocarlosandrada6657 2 месяца назад

You know if the OS can run with the pump removed or isolated some how?

@xKmotx Год назад

Of the two engines, in my opinion Thunder Tiger has the better engineering. I also am very impressed with the piston of the TTR engine, it required many machining operations to produce. The inclined valves and combustion chamber of the TTR are reminiscent of the hemispherical designs. And lastly, big bore will make more torque and swing a larger propeller. TTR for the win! 👍

@crazyengines88 Год назад

Thank you very much for your comment ! I also have the similar opinion regarding engine design - TTR shows more advance and sophisticated design solutions. But the most interesting should be "head to head" bench test comparison. Thank you !

@gecrashed6565 Год назад

I also have both engines, but the Thunder Tiger doesn‘t want to run on full throttle, after a few seconds it starts to make ratteling noises, the RPM drops, fuel shoots out from the carb and it stops so hard that the pro nut comes loose and the prop continues to spin freely. 🙉 What could be wrong with the engine? I have already opened it up before the test run, it looks like new. 🙂

@crazyengines88 Год назад

Hello and thank you for your question ! According to your description of engine's behavior it is showing the symptoms of detonation, so, engine runs too lean. Try to start carb adjustment from the beginning, you need to reset it (to return it to the factory settings, it should be described in the engines manual ), and start engine adjustment again. I've some plans to run Thunder Tiger 54 and 91 engines after a couple of weeks, I'll check, if your problem will happens on the bench. I'll make a video of this test runs, of course. Thank you and have a nice day !

@gecrashed6565 Год назад

Thanks for your reply! I have a 14x6 prop on it and the high speed needle was out ~3 turns, should be enough. Here is a short video of the engine: ru-vid.com6JpRbqUST0g?feature=share

@crazyengines88 Год назад

@@gecrashed6565 Thank you for your reply and for video provided ! Unfortunately, this video is too short, to clarify what's wrong. I'm sure, that the problem or in carb settings, or in too high fuel level, this could be the reason, why engine behaves like you explain. Regarding the card, some people recommends 3,25-3,5 turns and this is still close to lean settings. B.t.w., how long did the engine takes to break in? Was it sufficient ? So my opinion still the same - engine runs very lean or with to high fuel level. I'll recommend you to read this article, where you can find some recommendations about this engine : sceptreflight.com/Model%20Engine%20Tests/Thunder%20Tiger%20F-91S.html Thank you.

@gecrashed6565 Год назад

Thank you for your advice! I don‘t know how long this engine took to break in because I bought it on Ebay and the pre- owner said that it hasn‘t ran much.

@crazyengines88 Год назад

@@gecrashed6565 No thanks at all. I could offer to start from the beginning, so to reset the car to factory defaults, to mount engine on the stand (not on airframe), to start an engine with the richer settings, and to run it for 30 minutes with different carb settings. Doing so you can also learn a lot about your engine and its behavior. B.t.w., you can run it in "economy" mode, on the fuel without nitro content. During brake - in process it's now so important. Good luck !

@billjones3071 Год назад

Nice engines, I will never purchase engines with pumps in my opinion they are overly complicated and not worth the trouble especially if you’re just a sport flyer., thanks for the content

@crazyengines88 Год назад

Thank you very much for your comment, appreciated ! I also think so, because have some experience with OS pumped engines. Confirming, that its tuning is very tricky and sometimes complicated. Thank you !

@bloodnocka Год назад

Thank you for these engine comparison videos, they are well choregraphed and interesting to watch. Just a note on the Thunder Tiger; you made reference to the inclined angle of the valves! You will also notice on the top of the piston there are recesses machined to prevent the valves from making contact with the piston during operation. Please if you are unaware, this means the piston has only one orientation(direction) as the valve recesses are offset to one side. If the piston is assembled incorrectly the valves will hit the piston and could be damaged. I'm sure you may have already figured this out? Some of Thunder Tigers design choices from the day were a little unusual and advanced I feel. Have a great day.

@crazyengines88 Год назад

Thank you very much for your comment ! TT91 piston special surface shape is important part, agreed, and definitely, it should be added to this video comparison. I'll try to find the way, how to edit this video in RU-vid cloud. Thank you very much for your attention ! Have a nice day !

@bloodnocka Год назад

@@crazyengines88 You are very welcome.

@crazyengines88 Год назад

@@bloodnocka Thank you, appreciate for your support and attention !