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Does a true 4 stroke exist?

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Does a true 4 stroke exist?

Old 06-01-2022, 11:12 PM
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Default Does a true 4 stroke exist?

Basically what it says on the tin. Does a true 4 stroke engine exist for rc? Runs on gas, no oil mix. Thank you.
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Old 06-02-2022, 12:03 AM
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Nope, not below the 10cc engine size.
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Old 06-02-2022, 03:21 AM
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All 4-strokes are "true 4-strokes". Oiling method has nothing to do with the number of strokes per combustion cycle. It's true that 4-stroke engines commonly have a separate oil reservoir and 2-stroke engines commonly run on fuel with oil premixed into it, but that's not required by the number of strokes. There are 2-stroke engines sealed crankcases with oil inside, they just use turbochargers to provide the intake air supply instead of routing intake air through the crankcase. And there are 4-stroke engines that have a separate oil reservoir and run on premixed fuel and oil, for better upper-cylinder lubrication.

As far as running a RC car on a 4-stroke engine is concerned, you really wouldn't want it to have a separate oil reservoir anyway. You'd need an oil pump of some variety (even a very simple one consisting of a paddle on the underside of the connecting rod) to get oil up to the valves and camshaft, and you'd also need a crankcase ventilation system to prevent pressure buildup in the crankcase, which adds complexity and extra places for the oil to leak out. One tiny leak would cause the engine to oil-starve in a matter of minutes, and the g-forces experienced by a RC car when accelerating and cornering would make it very difficult to maintain a consistent oil supply. Back when fighter airplanes had piston engines, the designers struggled mightily with supplying oil when the engines were subjected to high g-forces.

With premixed fuel you don't have to worry about all that stuff; everything inside the engine is continuously lubricated with a fine mist of oil. As primitive as premixed fuel may be, it's the best solution for the tiny engines RC cars use, whether they're 2-stroke or 4-stroke.
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Old 06-02-2022, 07:34 AM
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Thank you for the feedback
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Old 06-02-2022, 11:23 AM
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Originally Posted by fyrstormer View Post
All 4-strokes are "true 4-strokes". Oiling method has nothing to do with the number of strokes per combustion cycle. It's true that 4-stroke engines commonly have a separate oil reservoir and 2-stroke engines commonly run on fuel with oil premixed into it, but that's not required by the number of strokes. There are 2-stroke engines sealed crankcases with oil inside, they just use turbochargers to provide the intake air supply instead of routing intake air through the crankcase. And there are 4-stroke engines that have a separate oil reservoir and run on premixed fuel and oil, for better upper-cylinder lubrication.

As far as running a RC car on a 4-stroke engine is concerned, you really wouldn't want it to have a separate oil reservoir anyway. You'd need an oil pump of some variety (even a very simple one consisting of a paddle on the underside of the connecting rod) to get oil up to the valves and camshaft, and you'd also need a crankcase ventilation system to prevent pressure buildup in the crankcase, which adds complexity and extra places for the oil to leak out. One tiny leak would cause the engine to oil-starve in a matter of minutes, and the g-forces experienced by a RC car when accelerating and cornering would make it very difficult to maintain a consistent oil supply. Back when fighter airplanes had piston engines, the designers struggled mightily with supplying oil when the engines were subjected to high g-forces.

With premixed fuel you don't have to worry about all that stuff; everything inside the engine is continuously lubricated with a fine mist of oil. As primitive as premixed fuel may be, it's the best solution for the tiny engines RC cars use, whether they're 2-stroke or 4-stroke.
So, I guess I need be more specific. I need a small, 10cc or lower, engine for a hydrogen powered project. So, i need one that has a separate system for the oil. I am not worried about g forces. It has to be or can be made quiet. Finally, it needs to able run for a prolonged period, hours or even days, without burning out at a constant speed. Hope that helps wittle it down.
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Old 06-02-2022, 11:53 AM
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I'm not aware of any that exist. You may be better-off taking a small 4-stroke RC airplane engine and fitting it with an oil metering pump, like what Wankel engines use, that drips a tiny amount of oil into the intake plenum, and lets the motion of the engine agitate the oil into a mist.
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Old 06-02-2022, 06:29 PM
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Upscale your project just a bit and use a Honda GX25
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Old 06-02-2022, 08:54 PM
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Originally Posted by wingracer View Post
Upscale your project just a bit and use a Honda GX25
I am looking at those. I was hoping i could go smaller, but doesnt look like will be able to.
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Old 06-04-2022, 05:50 AM
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Toyan makes miniature 4 stroke motors. They are pricey though. O.S. makes 4 stroke airplane motors. Not sure if any of these can run on gas or have a separate oil reservoir.
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Old 06-05-2022, 01:08 PM
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Originally Posted by sugs View Post
Toyan makes miniature 4 stroke motors. They are pricey though. O.S. makes 4 stroke airplane motors. Not sure if any of these can run on gas or have a separate oil reservoir.
thanks, I'll take a look at these
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Old 06-05-2022, 01:47 PM
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Originally Posted by sugs View Post
Toyan makes miniature 4 stroke motors. They are pricey though. O.S. makes 4 stroke airplane motors. Not sure if any of these can run on gas or have a separate oil reservoir.
Nope, the Toyan engines also run on a 2-stroke kind of fuel for the lubrication. Those engines have no oil channels, pump and oil in the crank case for a continuous lubrication. One thing that is different compared with other engines is that it has a system for cooling fluid.
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Old 06-11-2022, 11:52 PM
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Originally Posted by Roelof View Post
Nope, the Toyan engines also run on a 2-stroke kind of fuel for the lubrication. Those engines have no oil channels, pump and oil in the crank case for a continuous lubrication. One thing that is different compared with other engines is that it has a system for cooling fluid.
Darn. O well, those were expensive. Looks like the honda minis are my best bet.
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