Phoenix Strega motor for 120 class racing.
Hey guys,
I've decided jump up to the local 120 warbird class that's going to make it's debut this year. The class rules have not been formally announced yet, but my understanding is that it will allow a minimum wing area of 550in. This allows the Phoenix Strega I've got to meet the rules. The motors allowed are any FI/SE 2 stroke or 4 stroke under 1.2ci. There will be no ducted fan or dedicated speed motors allowed, this includes Jett.
I plan on sport flying the plane 99% of the time, but I'd like to be able to race it in this class on occasion. The options I'm currently weighing are the YS 110, an OS or YS 91 Heli motor with a tuned pipe, or the 120AX with a tuned pipe. They are all about the same weight with the exhaust systems.
A friend of mine is running a 120 AX with a tuned pipe on 15%. The 120AX turns an APC 11x12 at around 12.5k RPM on the ground. It unloads quite a bit in the air because it has been radared in the 145mph range (maybe 15k).
The YS 110 is reported to turn an APC 13x13N at 13k on the ground using 60% nitro. I'd imagine that it would gain at least another 1k in the air. That would put it in the 140mph range also.
The 91 heli motors are turning a 10x10 or 11x9 at 16k on the ground. I'd assume that they will unload about 1k in the air. On paper that is more HP than the 120AX is making but how it translates in the air in this airframe is unknown.
I like the idea of using the YS 110 as it's a proven setup, the exhaust system is much smaller and it will have that nice 4 stroke sound. On the other hand it will need lots of nitro to make the big HP needed at the races. The 91 Heli motors also intrigue me. I'm not a big fan of the tuned pipe hanging on the side of the plane, but I think that this may be the winning ticket. The fuel and propellers of the 91 will be the most economical, while the 110 props will be 4-5X more expensive and race fuel will be about 1.5-2X the cost.
So, what am I missing? What do you think would be the best option for racing? Which would be the most user friendly? Is there another option I should be looking into?
Thanks for your help guys,
Chris