airraptor

My Feedback: (66)

here is my Big one with me holding it on its side and then the two together.

airraptor

My Feedback: (66)

here is video of the little one racing. i am the guy in the red helmet later in the video not the guy in the first part with yellow plane. during the race the Shaw kid beat in the corners every time as I was flying to long but would catch him down the straight every time lol. cant beat the sound of YS engines on some nitro.

http://www.krcrtv.com/news/sports/re...erson/26612156

Tbobflow

Wow, thats pretty cool! Thanks for the link to that news article Airraptor

Tbobflow

Hello Gentleman!

After a hiatus I'm back to this project. I have made a few decisions regarding how I will be proceeding.

I will indeed run the engine. I will begin breaking it in soon, I look forward to building a test stand and sharing some video clips of the break in. Additionally I have decided that I will put the engine into a Hangar 9 Twist 150 ARF that I picked up last season. I like this choice as it will really show off the engine, the engine mounts upright in this airplane and doesn't have a cowl.

The recommended engine, a Saito 1.8 has a weight of 880g while the OS FS120SP is heavier at 1040g (actual weight on my scale) but with over 1200sq inch of wing area I doubt it will be an issue. The manual says the finish weight for the Twist 150 is between 8.5-10lbs.

So first step is to build a break in stand for the engine.

Thanks for reading and any advice or friendly comment are sure welcome!

Have a great day

Tbobflow

Still getting ready for this

does anyone one know if the exhaust port threads are the same between the fs91 and the fs120? In other words would an exhaust pipe be interchangeable between the two engines?

Sandyt

Tbobflow

No, they are very different. The SP has an unusual steel adapter with male threads on both sides. The threads in the head are much larger than the FS-91.

SandyT

Tbobflow

Yes, I see the steel insert in the exh port of the 120SP. I was hoping some of the straight pipes for the 91 would fit. I don't want to put the muffler on the SP.

1QwkSport2.5r

Why don't you want to use the muffler?

Tbobflow

I don't mind it being really loud, and I prefer the cleaner look of the straight stinger pipe

Tbobflow

Update: I bought a second engine that had already been run so that I can keep my NIB one on the shelf. I set it up in my test stand today and checked it out. I run it with the muffler on it and man it was still loud.

I saw 11krpm with a 13x10 prop and 20% nitro fuel with 170F head temps and glow plug temps over 210F, 250F one time before I added fuel. It spit back once and kicked the prop nut loose, I think my glow plug is too hot, too much ignition timing maybe.

I need to pick up a few extra glow plugs, need to lookup what is prescribed for this.

I still need to work on the idle setting, it looks to have a idle air setting screw on the carb but I'm not sure if that's what I'm looking at or not.

I can tell that there is a lot of energy in this engine, the exhaust note is obviously from a boosted engine.

booston!

Tbobflow

I think I need more like a 14x10 prop also, the 13x10 didn't seem to load the motor fully.

Tbobflow

So I got 14x10, 14x12, and 14x14 APC pattern props on the way as well as a couple OS type F glow plugs. Try these and see what's up!

Booston!

Bax

My Feedback: (11)

We used to run an APC 13.5 x 13.3 propeller on the FS-120SP engine, which was the recommended propeller at the time. The engine would turn around 10K or so with that prop, which was really good. We ran it with regular Omega 15% glow fuel and a #8 glow plug. That engine would usually need about 5 gallons' worth of running before it really came in and would develop its best power and handling.

Tbobflow

Someone warned me about one of the 13.x X 13.x APC props that were prone to breaking? Airraptor mentioned it I think.

airraptor

My Feedback: (66)

Yes the 13.5x13.3 might if have a lean run. They have a small radius from the hub to the prop. The replacement prop is the 13.5x13.5 from APC. I have run them as hard as 12,500 in the air and no issues. great prop. I run it on all my warbirds with the YS 115

Tbobflow

Cool beans. Get ready, I'm about to run 10k on a 14x14

Tbobflow

Interesting observation about the C14 carb and the advertised power output for the FS120SP. The carb opening is 0.213" diameter. Fully choked (i assumed choked condition at 5 bar differential) flow thru this diameter orifice at std temp and pressure at the inlet is 38cfm, or 2.66 lb/min flow rate of air. This is exactly how much air is required to make 2.5hp, which happens to be the official power rating for the engine.

The engine is completely carb limited to its advertised power level. I have a feeling that the motor will easily make 2x the power if it were not carb flow limited like this. Of course thats not really considering the strength of the parts or at what point parts of the engine simply break.

Tbobflow

I have 4 of these engines now, and none of them have the early carb with the larger barrel in it. Anybody know what diameter the early carb opening was?

Bax

My Feedback: (11)

Back in the day, we were told that the engine's output was limited because it was easy to overboost the engine and develop enough RPM that the engine would swallow a valve and then make some impressive noises as it self-destructed.

Tbobflow

Thanks Bax, I agree that extending the rpm would be a bad idea. The valve springs don't look up to the job and I'm already suspect they are floating at 11krpm. It would be perfect if I could electronically limit rpm with the ignition. Looking into that. Anybody seen a rev limit module that work with the rcexl CDI?

Tbobflow

7800rpm on the 14x14 APC pattern prop, no engine mods yet. 20% nitro.

Tbobflow

How is the connecting rod bearing on the crank lubricated? Virtually now fuel makes it there, correct?

Tbobflow

"Virtually no" I meant

ok, just ran the 14x10 APC narrow pattern prop, did 9500rpm. I'm using VP 4stroke YS/Saito 20/20 fuel.

13x10 11,000rpm
14x10 9500rpm
14x14 7800rpm

airraptor

My Feedback: (66)

Tbobflow, those number are equal to the OS 120 AX on it muffler with the 14x14 and the 14x10 is just about 300 more than the YS 91 AC. keep running fuel thru it to see what it does.

Tbobflow

Wife says I can't run it on the porch anymore

Need to make some saw horses.