Hi Bob,
I have noticed a difference in the black mufflers for the Jett 50. Just curious as to what, if any, the practical differences are. The one I have is in the first picture. The one in the second is slightly different.

Also, I noticed in another thread in the Jett support forum that you recommended ( among others ) an APC 8.5x 7.25 prop for use on small, fast planes. Sounds interesting. What rpm range should this prop run in, and should it be used on a relatively new ( bench ran only ) engine?

Thanks Bob,

Dave

Hi Dave......

the muffler you have there is the SJ-50 race muffler .... basically the same internally as the Q-500 black muffler shown in the other photo. Runs the same from what i have seen. It just replaced the double-bubble chamber with a straight one.

With the black muffler, if you have the engine installed on a Q-500 or something similar/quick, start off with an 8.75x8W, or 8.8x8.5 prop. You want to prop the engine to run over 18K rpm on the ground. Preferably up over 18,000 for launch. As the engine breaks in and you get some experince with it, you can experiment with props that work best on your airframe.

That 8.5x7.25, on a SS-40 engine (1 needle carb, SS red muffler) will turn upwards of 20K+ rpm on the ground. Hits over 21K in the air. Turns out that combionation had a secondary tuning node we found purely by accident some time ago, when we used the 8.5" props for break-in and early test flights. The engine really responded, and we noted that the test flight speeds and lap times were faster than with the 8.75x8W "Baseline" prop. So for regional/club racing, where they did not require 8.75" min diameter props, we used the 8.5x7.0 and 8.5x7.25 props for actual Q-500 racing. The SS muffler works similarly on the SJ-46 and SJ-50 engines.

Bob

Thanks Bob. Your advice is always appreciated. The engine will have a home in a Lyle Larson Vendetta, being built as we speak.

Again, thanks!

Dave

thats a good home You will enjoy it.

Thanks Bob. I have been getting the " stuff " up for this project for a couple of months now. It is currently in the hands of my friend Jeremy Ferguson, who is doing the build and paint. Problem is, with Jeremy's talent with an airbrush, I can't seem to decide on how I want it painted. Whatever we decide on, you can bet it won't look like a typical " stripes and numbers " QM 40.[sm=wink.gif]

Again, thanks for your advice and kind words.

Dave

Jeremy has produced some of the finest paint jobs on RC universe that I have ever seen--- Seems like a nice kid, is it expensive to use him? I always wanted a Whiplash custom painted by him.

Cheers!

Yea, Jeremy's a good guy for sure. One of the best friends I have. His paint is second to none. As for price, well, to quote Jeremy himself "good paint isn't cheap, and cheap paint isn't good"

His website is [link]http://www.lgmguitars.com/splash_guitars.html[/link] Tell him what you want and he can give you more info than I can.

My Vendetta should be ready in another month or two ( he's pretty busy right now). I'll post pics in the Extreme Speed forum when it's done.

Dave