Hello, I just got this small engine and have no idea of what to expect from it as this small size is new to me. I run it on a pipe and tached APC 7-6 at 17200 static. Does this sound ok, or should I expect more?? I have not fine tuned the pipe yet , so maybe there`s more to be had.

I'm not really sure about the power of that particular engine, but I regularly tach the Magnum 15XLS's at 17,750 RPM using 5% Wildcat fuel when the ambient temperature is 73 degrees and with 42% humidity at 1000 feet above sea level. These readings are the mean values from multiple engines and multiple runs, all of which are using a Master Airscrew 8x3 prop and the stock mufflers. I suspect this is the most commonly used prop for this size engine here due to it's use in RC combat, so either doing the math to adjust predicted values of the different prop or comparing it to the same prop ( easier ) would need to be considered. The Magnum is considered to be a relatively "hot" motor out of the box compared to some, but there are some competitive 15 sized engines turning upwards of 38,000+ RPM, so comparison is really relative to the manufacture. I have found RPM to vary drastically with differences in temperature, humidity and altitude, so unless those factors are accounted for, it is hard to say what you engine should produce. Nitro content from 5% to 10% only produced about a 200 RPM difference, assuming both were "fresh" fuel. I don't know if any of this helps, but it is my findings and it may give you a reference for comparison. Good luck.

BNC

I just cut the header shorter and got 18300 rpm static on APC 7-6, it really screams now

keep cutting 1/8 " off till theres no more improvement. you could still have some more to go .

I tried som Rapicon 45/20 fuel today and hit 18600 rpm on the APC 7-6, that`s 0.58 hp and the engine is rated to 0.5 hp

The header is very short now, so I don`t know about cutting it even more, but maybe I`ll give it a try

This is the pipe and header I`m using: http://www3.towerhobbies.com/cgi-bin...?&I=LXMMM0&P=0

I used a piece of alum. tube between the pipe and header, but now I use only the stock header length and I think it looks kinda short, but maybe I can shorten it further??

For comparising my freinds new XLS .15 turns the same prop at "only" 15600 rpm so I have an increase of 3000 rpm over stock engine

I just tried to cut off 0.5 cm and I got a peak of 19100 rpm, but it was very unstable and I wasn`t able to get a steady reading and it ran very hot, so I think I was short enough as it was.