Jett Stream muffler pressure...?
08-08-2004, 12:45 AM
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Jett Stream muffler pressure...?
Hello Bob,
I just received and test ran a Jett Stream muffler on my Webra .32 ABCD engine.
The engine runs just fine, that's not the problem. As a matter of fact it runs awesome...
The problem is I can no longer richen the engine up to the point where it dies... this engine is equipped with a Dynamix carb, and I'm running it on 10% fuel, so that may be part of the problem... Normally it's not build for that, but it works (worked) if I tune it right.
So, should I consider it to be normal that these "tuned mufflers" just have less pressure?
I just received and test ran a Jett Stream muffler on my Webra .32 ABCD engine.
The engine runs just fine, that's not the problem. As a matter of fact it runs awesome...
The problem is I can no longer richen the engine up to the point where it dies... this engine is equipped with a Dynamix carb, and I'm running it on 10% fuel, so that may be part of the problem... Normally it's not build for that, but it works (worked) if I tune it right.
So, should I consider it to be normal that these "tuned mufflers" just have less pressure?
08-09-2004, 12:21 PM
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RE: Jett Stream muffler pressure...?
Hi,
Thanks for writing.......
On the contrary...... typically the jettstream tuned exhaust create more 'tank' pressure and tend to have a better balance on backpressure. The turbojett muffler makes even more pressure. On the QM engines, we typically put the fuel tank back over the wing at the CG, and there is rarely any issue with fuel delivery.
I am familiar with the dynamix carb.... works well, however it does have some limitations since it is essentially an 'injector' body rather than a venturi.
You should at least be able to create a rich mixture to where the engine drops off into something of a 4 cycle. Are you able to get a stable, slightly rich mixture for flight?
Sometimes what happens, if you try to back the needle out of a dynamix beyond that 2/4 cycle break, the needle will begin to leak air, and the engine start to 'lean' itself out. Just a possibility.
10% fuel should be just fine. I have run my Webra heli engines (and the old Q500 engines) on everything from 5% to 40% nitro... they seem pretty versitile. My remaining Webra 33H is converted to aircraft use, with a turbojett installed. Runs like a watch. Does have the TN barrel carb though.
Thanks for writing.......
On the contrary...... typically the jettstream tuned exhaust create more 'tank' pressure and tend to have a better balance on backpressure. The turbojett muffler makes even more pressure. On the QM engines, we typically put the fuel tank back over the wing at the CG, and there is rarely any issue with fuel delivery.
I am familiar with the dynamix carb.... works well, however it does have some limitations since it is essentially an 'injector' body rather than a venturi.
You should at least be able to create a rich mixture to where the engine drops off into something of a 4 cycle. Are you able to get a stable, slightly rich mixture for flight?
Sometimes what happens, if you try to back the needle out of a dynamix beyond that 2/4 cycle break, the needle will begin to leak air, and the engine start to 'lean' itself out. Just a possibility.
10% fuel should be just fine. I have run my Webra heli engines (and the old Q500 engines) on everything from 5% to 40% nitro... they seem pretty versitile. My remaining Webra 33H is converted to aircraft use, with a turbojett installed. Runs like a watch. Does have the TN barrel carb though.
08-16-2004, 05:51 PM
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Problem solved!
Hello again Bob,
Problem solved!
My mistake: the spraybar wasn't properly aligned with the fuel injection point. Took me a while to figure that one out.
The muffler works like a charm.
Thanks for the help and sorry for the unnecessary post.
Problem solved!
My mistake: the spraybar wasn't properly aligned with the fuel injection point. Took me a while to figure that one out.
The muffler works like a charm.
Thanks for the help and sorry for the unnecessary post.
08-23-2004, 12:12 AM
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RE: Problem solved!
You wanted to know how the plane goes...? Well, it goes like stink!
The engine is mounted on a Diamond Dust, and it really unloads when it gets up to speed. The Webra does about 17000 static on an APC sport 8x8, which is nice by itself... but it really comes to life when the DD is passing the 100 mph mark (straight up).
I blew out two Rossi #3 plugs, because I didn't account for the unloading... I just didn't expect it to run THAT hard... just a tad too lean, and a long power dive, and there goes your plug...
Running R4's now, plenty rich on the ground, and screaming in the air. They hold up fine.
I am finished with mousse can setups... everything that needs to turn will get a Jett Stream from now on...
Say thanks to Dub from me for an awesome product.
The engine is mounted on a Diamond Dust, and it really unloads when it gets up to speed. The Webra does about 17000 static on an APC sport 8x8, which is nice by itself... but it really comes to life when the DD is passing the 100 mph mark (straight up
).I blew out two Rossi #3 plugs, because I didn't account for the unloading... I just didn't expect it to run THAT hard... just a tad too lean, and a long power dive, and there goes your plug...
Running R4's now, plenty rich on the ground, and screaming in the air. They hold up fine.
I am finished with mousse can setups... everything that needs to turn will get a Jett Stream from now on...
Say thanks to Dub from me for an awesome product.
08-23-2004, 07:16 AM
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RE: Problem solved!
Im glad things are working well 
Nothing like a good engine when everything comes together
If you have a chance, send me a few photos of the plane. I will put them in the Jett Hall of Fame page. it will be nice to have a DD in there with something other than a .50 on it
That R4 plug sounds about right for the job. Usually, I back my engines down about 500-800 rpm off of peak before launch. As you noticed, once it gets on the muffler, it needs the fuel.
Bob
Nothing like a good engine when everything comes together
If you have a chance, send me a few photos of the plane. I will put them in the Jett Hall of Fame page. it will be nice to have a DD in there with something other than a .50 on it
That R4 plug sounds about right for the job. Usually, I back my engines down about 500-800 rpm off of peak before launch. As you noticed, once it gets on the muffler, it needs the fuel.
Bob
