Ringed/Non-ringed Engines

[Anomie]

Ringed RC engines have a piston ring like most other engines - Cars, lawnmowers, etc.

Normal RC engines have no piston ring and I'm guessing the piston sits in the engine very snug to keep a similar seal.

I'm looking for pros and cons of each.

To me, thinking logically, ringed would be the way to go, less friction on cylinder walls. I could be wrong.

Thoughts?

[AaronS]

ringed engines typically require longer, more carefull breakin. If you run an engine to the point it needs to be rebuilt; with a ringed engine you can replace just the ring, where as a non-ringed engine you need to replace the pison and sleeve.

[Anomie]

ringed engines typically require longer, more carefull breakin. If you run an engine to the point it needs to be rebuilt; with a ringed engine you can replace just the ring, where as a non-ringed engine you need to replace the pison and sleeve.

That's it?

I'm assuming replacing the rings on these is just as easy as anything else. I'm guessing you'd need some sort of special tool to swap the rings?

[cbflys]

Non-ringed engines usually are higher performance than their ringed counterparts. This is due to the tighter tolerances between the piston and sleeve. You get less blow-by.

[jschief]

Non ringed engines use different metals that expand at different rates when hot which make the seal with the piston to sleeve.

I always thought the heli engines run a bit warmer than airplane engines because they rev higher and stay at that range thru the flight, compared to airplane engines that the throttle changes alot and you do not use full throttle all the time.

Isn't this the reason most heli engines are ringed? I also think the ringed engines break in quicker because the ring can cut in and seat better.