BME .90 gasser  
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BME .90 gasser - 10/28/2006 9:13:33 PM   
mrbigg



Posts: 2699
Joined: 10/30/2004
From: Streator, IL, USA
Status: offline 		I'm thinking of getting this engine and would like to try one of your mufflers for it. It will be on a profile plane. What kind of weight will I save over the stock one and will I pick up any RPM?

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PROVERBS 15:22 - Plans go wrong for lack of advice; many counselors bring success.
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RE: BME .90 gasser - 10/30/2006 5:12:10 PM   
bob27s



Posts: 4625
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi, thanks for writing....

Since the stock ST90 responds pretty well to the jett-stream, this engine should as well - but as usual, you have to select a prop that will allow the top end rpm to hit the best rpm to perform with the muffler.

However none of us have seen or tried the new gasser yet.

On the longer 90T muffler, (same as the 1.20 size jett-stream), you will want to prop the engine to run somewhere around 10-12K rpm on the top end. The BME is showing a HP number at 14K rpm, so Id tend to prop closer toward 12K if possible.

You should be able to gain 400-800 rpm over the stock muffler. Does not seem like a lot, but with larger prop sizes and power levels, that is a big HP increase. But keep in mind, the tuned exhausts tend to work best for more steady-state rpm. The boost provided does affect rpm for a given throttle position - sometimes you will experience a pipe step.... but that tends to be minimized when using the longer (lower rpm) setups. For profiles and 3D work, yes, they can be effective, when you take time to setup the engine/throttle/aircraft to make the best use of the configuration.

There may be an un-forseen effect of the gas/exhaust gas temperature when using either the jett-stream or turbo-jett muffler. That will only be seen by some experimenting. But I do not believe it will be a problem (just off hand).

As for weight/size, the info for that is on the jett website. The 120 size jett-stream weighs appx 200 grams. You will have to compair that with the stock muffler being provided with the BME.

Bob



< Message edited by bob27s -- 10/30/2006 5:14:16 PM >


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Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to mrbigg)
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RE: BME .90 gasser - 10/30/2006 11:06:36 PM   
mrbigg



Posts: 2699
Joined: 10/30/2004
From: Streator, IL, USA
Status: offline 		Thanks, Bob. That sounds like a decent increase. Your saying go with the 120 Jett -Stream?

_____________________________

PROVERBS 15:22 - Plans go wrong for lack of advice; many counselors bring success.

(in reply to bob27s)
       Post #: 3

RE: BME .90 gasser - 10/31/2006 4:52:27 PM   
bob27s



Posts: 4625
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Yes, that will work best. It is longer, tuned lower.

The standard 90 size version will require you to prop for between 12-15K rpm - probably not what you are looking for

Happy Halloween !




_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to mrbigg)
       Post #: 4

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> BME .90 gasser
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