RE: 140+ mph H9 Sundowner 50 Arf
I wouldn't mind seeing more of that 90LX installation.
I've noted to a few people that I dont really recommend the 90LX in this application. If it is not set up properly, or if someone adds a bunch of exhaust extentions to the setup, its just not going to work properly.
If he is running a crud load of muffler extentions, he needs to match the props better to the resulting rpm peak.
We have seen up to 135mph level flight with the 60LX installation. Done properly, the 90LX should get more than 5 mph better. The GP toni gets up over 130mph with a 90LX, and it is a bigger airframe. If not, then its obviously the wrong engine choice for the job.
Its still probably not going to match what a high-timed pressure-fed YS.91H can do. But it sure should come close.