gtisme

Soliciting opinions on removing oil scraper ring on 3 ring Ryobi 4 strk engine. I'm converting a Ryobi 26cc 4 strk to glow and am considering running it on low oil (5% - 10%) glow fuel with no oil in the crankcase. The only problem is that this engine uses 3 rings....2 compression rings and an oil control ring. With all 3 rings, there will be too little blow-by to keep the lower end lubricated. Regular glow 4 strks only use 1 compression ring allowing enough blow-by to lube the engine. I just don't know if the empty ring grooves might cause an unforeseen problem.

Any thoughts on this subject would be appreciated!

TIA

Gary

Captain Ramius

You're not going to gain a thing.even if the engine survived running in this configuration you'll have other problems.
IF the rings are leaking enough to allow oil past ,then compression will be lower and lose power.Lose a lot too.
Cam will not last very long.

Don't most of those big nitro four strokes has a bypass hole to feed lubrication to lower end and and some kind of evacuation?
Wouldn't blow by would only allow burnt oil to lubricate engine?

I could see an alky carb and a glow ignition to reduce weight, run engine with crankcase full of the proper oil and this should work.

TrevofKal

I would say have a go! Removing the oil control rings will have near NO effect on compression and you still have the 2 compression rings for that anyway. I would put some of the oil you intend to run in the fuel in the sump first though to give some lubrication to the lower end until its all coated from the running. Some of these engines have an oil slinger run off the crankshaft, you may even drop this from the "items required" list if you wish as there will not be as much oil in the sump to sling. I would also consider putting a vent from the rocker cover and partially closing off the regular crankcase vent to make the escaping blow by drag some lubricating oil around the rocker gear on its way out of the engine.
If the crank is all roller bearinged, I think you could safely use 5%oil, otherwise stick to around 10% for a little safety with the plain bearing style.
Dont worry about the "burnt" oil issue brought up previously, the engine wont burn oil unless its temperature skyrockets considerably. Engines burn fuel, and use oil.
Before flying the engine though, I would give it a good hours bench running to make sure everythings tikketty-boo.

gtisme

Thanks for your replies! The rod has rollers at both ends and a splasher on the bottom. I'm trying to get a little extra power out of the engine with the glow, and be able to run this motor in an inverted mount. It can be run inverted with oil in the sump, but as much as 1,000 rpm's are lost due to the oil moving into the bottom of the piston.

Regular glow 4 strk's are well lubricated with the blow-by from the single compression ring and valve stems without seals.

Thanks again for your input!

Gary

airbornrc

My Feedback: (9)

The purpose of an oil scraper ring is to remove excess crankcase oil from the cylinder wall, not to seal compression pressure. Removing the ring will not allow oil from the combustion chamber into the case. Think about it the compression rings are sealing the gasses in the chamber why would they pass liquid? Sounds like a train wreck waiting to happen to me.

Mark

Captain Ramius

That was my point airborn.
Glow engines are designed to run with the oil supplied in the fuel that particular engine was not.
Without a good supply of oil to the cam will soon have metal particles circulating inside it also.

You can try it, it would be interesting to see the results, if you are successful thats great but I think you are going to wind up disappointed.