Best muffler for OS 91 FX?
12-13-2004, 01:41 PM
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Best muffler for OS 91 FX?
Has anyone tried several different mufflers in an effort to figure out which one gives it the best performance?
How about some RPM numbers with your muffler.
I am going to test a SLIMLINE and a BISSON. Will report
How about some RPM numbers with your muffler.
I am going to test a SLIMLINE and a BISSON. Will report
12-13-2004, 01:46 PM
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RE: Best muffler for OS 91 FX?
If you are really looking for performance, get a performance Specialties Ultra Thrust muffler. There are 2 sizes for the OS .91FX, a long chamber one for the 14-6, 15-4W, 16-4W props and a short chamber one for running 12-8 & 13-6s. they add 800-1200 depending on the prop.
If you want a Pitts style, see Jett Engineering for their underslung tuned muffler.
If you want a Pitts style, see Jett Engineering for their underslung tuned muffler.
12-17-2004, 10:56 AM
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RE: Best muffler for OS 91 FX?
As was noted above,
Jett has two tuned exhaust muffler for the OS91 that provide outstanding performance. Perhaps I can expand upon that a bit.
The jett-stream side exhaust muffler works very well. The same muffler used on the Jett 90L. The OS responds quite well.
For scale and aerobatics use, the Turbo-Jett muffler is a great choice. The OS 91FX utilizes the 10cc version, and responds particularly well especially with larger props.
example performance from testing data (peak ground rpm):
APC 14 x 6 OS muffler 10,700 RPM Jett-Stream muffler 11,600 Turbo-Jett muffler 11,500
Other prop/performance numbers can be found [link=http://www.jettengineering.com/accy/turbo.html]here[/link]
Photo is an example of an [link=http://home.comcast.net/~keblair/Extra300s.htm]Extra 300 with a OS91FX and turbojett installation[/link]
I hope this is helpful
Bob
Jett has two tuned exhaust muffler for the OS91 that provide outstanding performance. Perhaps I can expand upon that a bit.
The jett-stream side exhaust muffler works very well. The same muffler used on the Jett 90L. The OS responds quite well.
For scale and aerobatics use, the Turbo-Jett muffler is a great choice. The OS 91FX utilizes the 10cc version, and responds particularly well especially with larger props.
example performance from testing data (peak ground rpm):
APC 14 x 6 OS muffler 10,700 RPM Jett-Stream muffler 11,600 Turbo-Jett muffler 11,500
Other prop/performance numbers can be found [link=http://www.jettengineering.com/accy/turbo.html]here[/link]
Photo is an example of an [link=http://home.comcast.net/~keblair/Extra300s.htm]Extra 300 with a OS91FX and turbojett installation[/link]
I hope this is helpful
Bob
12-17-2004, 11:51 AM
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RE: Best muffler for OS 91 FX?
Bob,
That is the same plane that I am using the 91FX in. I do not have a cutout made in the cowl yet for a muffler because I wanted to try to figure out which one gave the best 3D performance. I am going to be swinging some larger diameter lower pitch props. Looking at the chart on the JETT web site, it looks like you really start to gain higher rpms when the engine spins upwards of 12-13 thousand rpm. Gains at these levels seems to be 11-1200. When you slow the engine down a little with a bigger prop, it seems as though there is still pretty substantial gains. At 9-10.5K rpm, it looks like 900 rpm is typical. NOT BAD AT ALL...... The only issue I see is that the muffler is a little heavier than some of the other after market mufflers for this engine.... LOOKS PRETTY GOOD OVERALL
Thanks for the info.
That is the same plane that I am using the 91FX in. I do not have a cutout made in the cowl yet for a muffler because I wanted to try to figure out which one gave the best 3D performance. I am going to be swinging some larger diameter lower pitch props. Looking at the chart on the JETT web site, it looks like you really start to gain higher rpms when the engine spins upwards of 12-13 thousand rpm. Gains at these levels seems to be 11-1200. When you slow the engine down a little with a bigger prop, it seems as though there is still pretty substantial gains. At 9-10.5K rpm, it looks like 900 rpm is typical. NOT BAD AT ALL...... The only issue I see is that the muffler is a little heavier than some of the other after market mufflers for this engine.... LOOKS PRETTY GOOD OVERALL
Thanks for the info.
12-17-2004, 01:56 PM
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RE: Best muffler for OS 91 FX?
Hi Capt....
Yes, it is slightly heavier. But its just the nature of the beast. Its not 'hollow" inside. The extra grams is only a problem if it affect the CG. Most folks tell me the planes need the nose weight anyway. It does package well in the airplane. If you notice in the photos, you have to "moon" out the lower front of the cowl a bit to clear the front of the muffler.
The turbo-jett is very broad band, and tends to turn an engine into a "torquer". We find that rather than climb in RPM, the turbo tends to allow you to go up in prop size and still keep that same rpm you had before. The OS91 with a 15x6 pulled very nicely. Probably the best prop match for aerobatics work, and likely for 3D. The OS was only about 400-500 rpm off from where my Jett 100 turns that same prop. Real good performance. (the Jett BSE-100 turns a 15x8 where the OS turns the 15x6 for comparison).
Aeroworks used the OS91/turbo combination for some of their developement work on their 60/90 size Edge.
Yes, it is slightly heavier. But its just the nature of the beast. Its not 'hollow" inside. The extra grams is only a problem if it affect the CG. Most folks tell me the planes need the nose weight anyway. It does package well in the airplane. If you notice in the photos, you have to "moon" out the lower front of the cowl a bit to clear the front of the muffler.
The turbo-jett is very broad band, and tends to turn an engine into a "torquer". We find that rather than climb in RPM, the turbo tends to allow you to go up in prop size and still keep that same rpm you had before. The OS91 with a 15x6 pulled very nicely. Probably the best prop match for aerobatics work, and likely for 3D. The OS was only about 400-500 rpm off from where my Jett 100 turns that same prop. Real good performance. (the Jett BSE-100 turns a 15x8 where the OS turns the 15x6 for comparison).
Aeroworks used the OS91/turbo combination for some of their developement work on their 60/90 size Edge.
12-17-2004, 07:25 PM
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RE: Best muffler for OS 91 FX?
Cap, I called my bud up, the one that did the test of the above mentioned Magum 91 muffler. I asked him if he recalled how much gain I was getting swinging a 14X6 and it was more then I thought. I was getting an extra 900 RPM apposed to the said 600 RPM form the mag muffler, as far as muffler weight I'd be willing to bet its a bit lighter then the FX91 stock muffler.
I am currently running the above setup along with a Perry pump in my 60-GP ucando 3D and its more then enough power. Plane wieght 7.6
Blackie
I am currently running the above setup along with a Perry pump in my 60-GP ucando 3D and its more then enough power. Plane wieght 7.6
Blackie
12-17-2004, 10:02 PM
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RE: Best muffler for OS 91 FX?
Thanks Blackie.... I may have to give that one a try as it is considerably cheaper..... I think by the time I am done figuring out which one to use, I am going to have several for sale..
