Jett Stream for OS 55AX
 

I can't remember where I heard this, but I think I heard that there are different sizes of Jett Stream mufflers based on the rpm and load. In my case, I want to run an APC 11X7 on an OS 55AX, does Jett offer a muffler for this application? I know it has to be longer than usual since I think the usual Jett Stream is for something like a 10X7. Can you please explain this to me Bob? I think I read there was like a 6.5 in, 7.5 in, and 8.5 in mufflers.

RE: Jett Stream for OS 55AX
 

Hi, and sorry for the delay.

For the 55AX you use the standard TT-46 size Jett-Stream. Nothing special. We do not size them by length, only by application and engine.

I would recommend an 11x6 to start with. You want the engine turning over 14,500 peak ground rpm. In fact the first few flights and break-in with an 11x5 is a good idea.

The combination of 55/Jett-stream/11x6 is just magic. Many aircraft out there flying like that. There are a few old threads in the Extreme Speed forum that can attest :)

Don't get hung up on the traditional prop sizes. :)

What aircraft will you be powering?

RE: Jett Stream for OS 55AX
 

Bob,

This setup is for a H9 Phoenix 7. Perhaps traditional, but an 11X7 works very well for this airplane, and most vintage pattern planes from the 70's. I probably should try a full tuned pipe, but i hate dealing with tuned pipes. The Jettstream just seems like the easy way out, just wished they were a bit more quiet. Oh, one more important question, can you tell me if the Jettstream provides at least as much muffler pressure as the stock muffler? It's important on this plane as it tends to go lean on outside maneuvers due to tank location and low muffler pressure will just exacerbate the problem.

RE: Jett Stream for OS 55AX
 

Listen to Bob, the max APC prop you can run with the Jett muffler is 11X6 for best performance. You can run a Master Airscrew S-2 Series 11X7(dark gray) , I actually prefer this over the APC in this application for ballistic vertical power and speed.
The muffler pressure is fine with the Jett muffler. If you have pressure problems with this, you would with stock muffler or tuned pipe as well. The H9 Phoenix 7 shows the engine mounted sideways, this is carb optimal for acrobatics.

RE: Jett Stream for OS 55AX
 

Do not get hung up on prop size numbers. An APC 11x6 puts out a bunch more speed and thrust in flight than an old Rev-UP 11-7 did 20 years ago. And as I noted, there is a lot of experience with the OS55/Jett/11x6 combination. Yes, you can run the 11x7, but get some run time on the engine first learn its tendencies, then experiment with props. Key as I noted rpm select a prop that will get you easily over 14K peak ground rpm.... then back off 500-600 rpm for flight.

If you have your heart set on an 11x7, get one from Vess. Outstanding good looking wood blades.

The Master Airscrew noted also works great too. Worth trying.

The jett stream will put out more muffler pressure than most stock mufflers. It also has a better balance of back pressure that makes fuel delivery second to none.

RE: Jett Stream for OS 55AX
 

I have 2 OS .55AXs that I have used my JettStream muffler on. It's a great combo. I gained 1700 rpm on an APC 11-6 and 1500 on an APC 11-7.

I used to run a lot of tuned pipes, but with the Jett Stream, there's no fuzz, no muss, no bother. Just bolt on, tune and hang on. It's so easy it ought to be criminal compared to cutting the header and testing and cutting and testing and cutting and testing...

Try the 11-6. You'll be smiling after your first flight.

RE: Jett Stream for OS 55AX
 

:D