1QwkSport2.5r

I put an APC 13x4W on an Italian G51 and got 10,800rpm peak on 5% nitro 20% castor and Bowman ring. Really, it needs a lot of runtime before it will be 'happy' turning the big props. My G51 was plenty rich in the midrange and it was slow to spool up on the 13x4. I think the liner is a little worn on mine as compression is mediocre, maybe it will handle more nitro.

What rpm did you get on the 12x6? APC or MA?

jeffie8696

Finally got my Italian GS 40 up today. Its quite a strong runner with a 10X6 prop.

Scrubmonkey

i havent got a tch but by ear it sounds as though it is turning about the same. it has square tips so its not as efficient as the R.A.M. prop which probably not as efficient as the apc. i believe the engine had had alot of run time on it befor i got it. and it hasnt got as much pressure as id expect or like but this is the first and only ringed engine ive got

1QwkSport2.5r

I'd invest in a tach. I think they are good to have.

What kind of rpm did you get with that GS40, Jeffie? ABC or ringed?

jeffie8696

I was in a rush and didn't have time to tach it. I think it will be around 13,000.

jeffie8696

If I remember right its a ringed engine.

hsukaria

I don't know about any old-time 40, but the GS-40 is ringed. I had one on a Quickie (GP Viper) with a 8.75x8.75 prop and I got 15,100 rpm. I was using a MACs one-piece muffler because the stock ST muffler would drag on the ground.

1QwkSport2.5r

The GS40 came ABC or ringed.

hsukaria

I was trying to say that in the past few years (Chinese made), it only sold as ring.

1QwkSport2.5r

They might have used up some leftover liner sets because I've seen on the big auction site both ringed and ABC Chinese made GS40's. At least that was what the description said. I don't know for fact (yet) if they still make them ABC. Then again, I don't think ST is making anything right now based on the scarcity of spare parts.

hsukaria

I was just basing my comment on what has been advertised in Tower Hobbies. I did not check the other sites.

downunder

AFAIK the GS40 has always only been ringed while the GS45 is ABC then up to the G51 ringed.

hsukaria

that's how I understood it since I got started in this hobby 7 years ago. I just wasn't sure about past iterations. The GS40 I had in the Quickie was ringed, but it had quite high compression.

jeffie8696

My 40 doesn't have the best compression but it does run well anyway.

1QwkSport2.5r

I must have misread what I had seen or the owner had it wrong. I could not find any information on any ABC GS40's. I stand corrected.

hsukaria

As far as using a ringed engine on a racing plane, I wasn't sure that was the best application. I would think that for high-revving engines you would want an ABC/ABN engine to get around the pistion ring limitations at high rpms. But I had purchased that plane used and it came with a ST GS40. Typically, those planes use ABN engines like Thunder Tiger Pro 40. The engne ran well at 15000+ rpms however, and was way too fast for my flying skills.

1QwkSport2.5r

Yeah, IIRC R/C ringed engines tend to have ring flutter above 16,000rpm though thinner rings flutter less and at a higher rpm than thicker rings. Now what is considered thick or thin is beyond me.

I've ran my S29 up around 17,000rpm and hadn't noticed any weird phenomenon with it. Do you or anyone else know how to tell if your ring is fluttering?

hsukaria

Sorry, I don't know anything about it, except that it exists.

1QwkSport2.5r

Due to some weird circumstances, I had to send my SuperTigre S90K off to get bearings installed. I normally do these myself, but I found out the rear bearing is a weird size and that sleeving the front housing allows the use of a standard bearing. Has anyone else had to do this of go this kind of route on the older ST engines? I had Paul at Rc-Bearings do the work. I guess the rear bearing is a Y17 which are hard to find, I think the replacement is a 6903 or something.

hsukaria

I noticed that the Super Tigre G51 has not been available in Tower Hobbies for some time now. Their listing says "Order Pending". I wonder if the factory is not making more? My G51 has been a dependable workhorse for 6 years with frequent usage and no problems.

1QwkSport2.5r

I received my front housing back from Paul at RC-Bearings today. I asked to have the old bearings sent back with the housing so I could look at them. The front bearing wasn't too bad, slightly loose. The rear bearing was indeed loose. This engine had a serious vibration problem no matter what prop was on it. I think I can pin the vibe problem to the bearings. The housing was sleeved to use a standard sized bearing and now is much tighter. I will run the engine later today or tomorrow and see if that was the source of the vibration.

Hsukaria - ST parts and engines have been hard to get from China for quite awhile. Nobody really knows why, including Tower & Hobby Sevices. Kinda hokey. You'd have better luck getting a TT or Evolution than a ST it seems.

jeffie8696

Check with Great Planes, they have parts available through the service department.

hsukaria

I have a question regarding compression in a ringed G51. I have had this engine for some time now and run it frequently. It has good power, but when not running, it has very little or no compression when I flip the prop by hand. Is that normal? I have other ringed engines that have a good compression when turned by hand. Any suggestions? How do I know for sure when it is time to replace the piston ring?

Basil Yousif

My Feedback: (3)

Here's the answer someone gave from another thread for the same question:

If I recall correctly, your engine is a ringed engine and not ABC. You used a fuel which contains castor in it (Coolpower is best for ringed engines) and it is possible you have a stuck ring. In addition, some engines use dykes rings which require combustion pressure to press the ring against the cylinder for a seal. I wouldn't worry about it. Squirt 3-4 drops of fuel in the carb, turn her over, and fire her up with a starter and see how she behaves.

Scrubmonkey

mine is the same and ive wondered if it needs a new ring and if it would get any more performance. mine has ok-low compression before starting, starts first flip and will run fine. but after wards there is practically no compression. and i think what basil yousif said might have come off of the thead i posted a while back aking the same thing. ive just come to live with it. she runs fine, doenst dead stick so im happy