I bought a China made engine, SC 46, and I do know they are supposedly to be not as good as a TT or OS and of course no where near a ROSSI. I am keen to know what level of performance and engine should have. Running it with a Bolly 10.5 x 7 I am getting about 12.8K RPM. Is that considered good for the prop size? Anyone knows of any document that can tell me what performance is deemed good or great? Thanks!

Seems ok if it was a good deal- An OS-46FX would get you 14K with a similar set-up

What are u flying with it?

Woooooow ... that much difference with an OS, hmmmmm ... I am having it on an EZ Laser 200, a very very old one. It was a great deal at about USD65.00, hehehehe ...

I wouldn't necessarly count on the OS being that much more powerful. A 10.5x7 isn't a common prop in the US, so I doubt you'll find actual tach readings on that engine to compare to. Your best bet is to find someone local and tach their engine.

Also, keep in mind that where you are makes a big difference. You loose a lot of RPM as you go up over sea level. Air temp and humidity play a part there as well.

Oh, and off the cuff, for around here, 12.8k on a 10.5x7 sounds pretty good to me, with a 10x7, I'd expect that to climb to 14k, which isn't out of line with the OS by much.

Oh, sometimes just changing mufflers can pick up RPM as well. The TT stock muffler or the Tower muffler both will increase the RPM on an OS over the stock OS muffler.

I agree, 12.8K on a 10.5 X 7 prop sounds decent. If the engien was indeed $65 USD, then I'd say it was a fairly good deal. Of course, the engine could wear out after a gallon of fuel, then the good deal goes away.
Dennis-

That is a very respectable rpm for that prop on the engine. Don't worry about it.

Nothing wrong with 12.8K, just throwing a comparison in the mix-

Your mileage may vary!

That is close to the performance you would get with a O.S. LA .46. (O.S.'s cheaper line of engines) which usually costs $20 more than whay you paid for your engine.

Its not bad. Its just not up there with a better engine.

**********

BTW... there is a hobby shop in Waco that carries the Bolly Clubman props. I've used the 10.5X6 and 10.5X7.

Throw a 10x6 on it, then come back and tell us what kind of rpm's your getting compared to your 10.5x7

Gary

I wouldn't run a 10X6 on a 46, not enough load for the engine. Sure you'll get much higher rpm, but you'll be above the power curve and actually lose performance rather than gain anything.
Dennis-

Love all this prop stuff. [sm=drowning.gif][sm=confused.gif]

I have had an SC 46. Its still screamin reliably in a mates Speed air.


Best of luck

Thanks for the feedback guys. I tried a 10x6 and I got too much cavitation, a lot of RPM but not pushing much air. I do understand that humidity and all will affect the performance, I was enquiring so that I can get a baseline guide to work with. Was my first time buying the engine and I was more of testing it than anything else. I have to say the SC is totally reliable, does not cut on me even when its running inverted. The power is less but the price is even lesser! I just got a SC 91 2C yesterday for my pattern plane ... hope it turns out well ... thanks a lot guy for your input!!!

ps. the SC is actually OEM for Magnums.

Well... I haven't heard it called cavitation when referring to an airplane prop before... but I have noted that you can stall the prop by turning too high an rpm at too low an airspeed. Cavitation normally refers to forming air bubbles with a boat or ship's prop when you "stall" it in the water. The phenomenon are similar in that each will show a loss of effective thrust compared to the rpm. Both also increase the noise produced.


Sometimes... you want to spin the engine up to a high RPM by using a lighter prop load. My recent problems getting an O.S. .46 LA to run properly were finally overcome when I used a 10X4 to unload the engine. The light load allowed it to turn an rpm that finally brought the engine up to correct temperature. Trying to run it lean enough to get above 7k rpm with the 11X5 or 10X6 just wasn't working (it was running cold... and just died if leaned more). NOW the thing is turning a 11X7 at 12,500 rpm, which is appropriate for the LA. (I guess I had to show the engine how fast I wanted it to turn a prop .)

Note... from my experience with the Magnum XL series... I wouldn't expect much better performance with Magnum's .46 than what I got from the O.S. LA. Maybe 13K with a 11X7 when its running correctly. Magnums seem to be good reliable engines... but not the highest power sport engines on the market. Good "bang for the buck" though. (cheaper than the LA... a little more powerful too.)

I only ever ran my SC 46 on the recommended 11x7 prop. it always seemed happy and still is running great! now in a mate's plane.

You are one bad dude ... I used to jet ski and that was the term for bubbles forming underwater! Hahahaha ... okay I am not nuclear scientist, hehehehe ... heck I am a layman. Of course if I wanted good performance it would have been the OS50SX or a nice little Rossi ... those babies can really turn a prop fast. Again the difference in cost between the OS46 and SC 46 on my end is great, the SC 46is like 60% of the price of the OS 46FX. That is the vast difference in cost compared to 1,000 RPM lower performance. Anyways, I am just in it for the hobby. Not for unlimited verticals! Hehehehe ...