My HOR made its first flights yesterday. About time, since we've been putting kits together for friends, and selling them at cost. I'm sure some of 'em were getting worried that they were buying an unflyable pos. Flies great, BTW.

Problem is, I'm gonna have trouble keeping my Magnum from exceeding the 17,500 RPM limit in SSC. With a brand new, piston and liner, on 5% fuel, it was turning 16,800, running rich. It's only going to get stronger, and I'm sure it's going to top out close to 18,000.

How do I slow it down to meet tech inspection? Granted, I'll probably be doing the tech inspections myself because I'm the club expert on SSC, but I want to be fair...

If I richen the engine, it'll still peak out when the fuel line is pinched. The only possibility is to go to 0% nitro, as far as I can see, but I'm not sure that'll help much.

My Magnum .15 requires a YS 20/20 fuel (20% Nitro 20% Oil) to get a contest inspected 17,300 rpm on the ground. 30% heli fuel let's it tach around 17,800 rpm, just a hair over. The main thing in SSC is making sure that engine runs the same the entire round.... that's where your sucess lies, but you need to be as close to 17.5 as possible at launch. Go up to 10% and see what happens.

Regards,
GPB

My problem is, once it's broken in, it's going to easily exceed 17,500. Going up to 10% is only going to make the engine run faster!!!

I want to make the engine run SLOWER.

I don't know what you're doing, but as far as I can see, you don't need to be pushing the ragged edge for these planes to fly well. The point here is SLOW, SURVIVABLE combat and piloting skill, not "eek out every last ounce of performance to get an edge on the other guy."

"Problem is, I'm gonna have trouble keeping my Magnum from exceeding the 17,500 RPM limit in SSC. With a brand new, piston and liner, on 5% fuel, it was turning 16,800, running rich. It's only going to get stronger, and I'm sure it's going to top out close to 18,000. "

With 5%, what did it pinch at? I've never heard of anybody not passing the pinch test using 5%. I normally need 15-20% to get to my target of 17,300-17,400rpm. My tach is always under what the official tachs have been reading, so I shoot for something below 17,500.

I just bought a jug of nitro, so I can match the nitro content at the field to get what I need without having to carry 2 or 3 extra bottles of pre-mixed...

Well, sir, you must have an exceptional Magnum .15 because as stated before, I have to have 20% nitro to get mine to perform close to 17.5 limit. Regarding performance, it has been my experience that unless the engine is taching right at the rpm limit, the performance of the airframe is greatly reduced. This is sort of like "restrictor plate" racing in NASCAR.... in order to compete with everyone else, you have got to be right at the rpm limit.

The Mag 15 does vary a bit from engine to engine. I have 4 of them for my A class planes, and I try to keep track of which is which, since some pull harder than others. Maybe it's just me and the way I treat my engines though. Anyway, I'd say just let it break in, and see if, in fact, you get to the point were you have to worry about it. I doubt even the best of them will hit over 17.5 on 5%.

fwiw, I was hitting 17.3ish last weekend, on 15% Omega.

Oh, it seems the blue props spin up lower than the black ones, btw.

Hmmm, I wonder if the rules could be adjusted to allow "restricter plates" to be put over the carbs of hot engines to tone them down to the proper RPM limits. Should be easy to do, and we could get rid of all the engine rules except the rpm limit.

Mike,

congratulations on the 2nd place finish in SSC, see you sunday!

Yep, that GCBM R/C Models Inc. Batty Bat powered by high quality Byron Originals Fuel was runnin' that unbridled power Magnum XL .15 'bout as fast as it could go. I wuz runnin' real good even though those boys were bumpin' me and tryin' to put me in the ground and such. Next time I'll get first place as long as my sponsors can afford to send me to the contests and pay me millions of dollars to use their products.

Regards,
GPB

Try moving your spray bar in or out. Going out usually increases rpms. In should decrease it