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Jett Stream muffler question

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Old 03-05-2011, 05:21 PM
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1QwkSport2.5r
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Default Jett Stream muffler question

I bought a Jett Stream muffler (red) for my TT .46 Pro. The muffler looks amazing - looking forward to trying it out. My question is this.. The port on the muffler and the brass gasket are smaller than the exhaust port on the engine itself. The height is the same or very close, but the width on the muffler is .710" +/- a teeny bit for error and the engine exhaust port is .940" wide. Is this going to hurt performance or is this done on purpose? I assumed the ports should be the same size and shape engine to muffler.
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Old 03-06-2011, 09:19 AM
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Default RE: Jett Stream muffler question

Same with mine, but it really boosts power nevertheless[8D]
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Old 03-06-2011, 11:24 AM
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Default RE: Jett Stream muffler question

not to worry.......

the port size does not matter. Hundreds of them out running on TT, OS, ST .... about all engines, no issues.

Bolt it on, and run it. Try to target 16,000 rpm or higher with your prop selection. A 9x7 is a good place to start.

Set the needle about 600-800 rpm off of ground peak for flight.

Bob
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Old 03-06-2011, 12:42 PM
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Default RE: Jett Stream muffler question


ORIGINAL: bob27s

not to worry.......

the port size does not matter. Hundreds of them out running on TT, OS, ST .... about all engines, no issues.

Bolt it on, and run it. Try to target 16,000 rpm or higher with your prop selection. A 9x7 is a good place to start.

Set the needle about 600-800 rpm off of ground peak for flight.

Bob
Just making sure on the port size.. I figured it was like that on purpose but I'm no expert, obviously.

This engine/muffler is going to be used on a hydroplane airboat, so there isnt any flight involved.. (at least not intentional) I plan to set the engine about 300rpm rich of peak since it wont be unloading at all. I'm also aiming at using a 10x5 or 10x6. I want good speed from the boat.

I tried the muffler out on one short run today and managed 14,740 using 15% nitro/22% oil and an APC 10x6. I only ran it for a few minutes because my fingers froze adjusting the needle.
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Old 03-06-2011, 05:07 PM
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Default RE: Jett Stream muffler question

a little less prop to start with.

You want the engine up closer to 15,500 for the muffler to really be killer.

Start small, and as you get time on the engine/muffler... then go up in prop.
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Old 03-06-2011, 06:26 PM
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Default RE: Jett Stream muffler question


ORIGINAL: bob27s

a little less prop to start with.

You want the engine up closer to 15,500 for the muffler to really be killer.

Start small, and as you get time on the engine/muffler... then go up in prop.
Alright Bob, I will pick up a 9x7 and see what it does. Thanks for the help. Even running on the bigger prop, I noticed a significant change in how it throttles on the pipe vs. the stock muffler. I look forward to seeing what this little machine is capable of.
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Old 03-08-2011, 02:45 PM
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Default RE: Jett Stream muffler question


ORIGINAL: bob27s

a little less prop to start with.

You want the engine up closer to 15,500 for the muffler to really be killer.

Start small, and as you get time on the engine/muffler... then go up in prop.
I went and picked up a 9x7 and 10x5 APC props the other day and had a chance to run the 9x7 today. Peak rpm was about 16,400rpm. Tached it two or three other times at right around 15,900-16,200. I'm gonna need some thrust for pushing a 5lb airboat around, so I'm gonna test the 10x5 when I get time.

Whats the lowest RPM I should be at to still have it using the pipe well?
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Old 03-18-2011, 05:25 PM
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Default RE: Jett Stream muffler question


ORIGINAL: 1QwkSport2.5r


ORIGINAL: bob27s

a little less prop to start with.

You want the engine up closer to 15,500 for the muffler to really be killer.

Start small, and as you get time on the engine/muffler... then go up in prop.
I went and picked up a 9x7 and 10x5 APC props the other day and had a chance to run the 9x7 today. Peak rpm was about 16,400rpm. Tached it two or three other times at right around 15,900-16,200. I'm gonna need some thrust for pushing a 5lb airboat around, so I'm gonna test the 10x5 when I get time.

Whats the lowest RPM I should be at to still have it using the pipe well?
I ran an APC 10x5 on my TT .46/Jettstream and got 15,500rpm pretty consistently with a few peaks at 15,800rpm. I think this is going to be the prop to run on the boat. Bob - any thoughts on this and my last post by chance? The lakes around here will be thawed out pretty soon so I'm eager to get out and do some more testing.
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Old 03-20-2011, 11:49 AM
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Default RE: Jett Stream muffler question

That should work ok for you...... see how it works.

What I might suggest while waiting for a thaw ....... is if possible, put that engine on a test stand. Take and old prop (10x6, 9x6, what ever in that range) cut it down to 7.5" diameter and balance it. Run the TT46 on the test stand with that prop start it a bit rich, and take it up to 16,500 with it still being slightly rich. Get a 3-4 tanks on it like that - occasionally lean it out to 17,000 (no higher for very long). After that... put your 10x5 back on... see how it performs.

Reason I suggest this ....... is your engine seems a bit down on rpm. A stock TT40pro with stock muffler and a 9x6 will turn 16,500 when properly broken in. That seems to be where its power band is. With a Jett stream on it we can typically go up to a 9x7 and keep that 16,500 rpm mark (ground rpm). The TT46 typically performs about 500 rpm higher. The main thing is breaking in the engine so it wants to run at 16,000+ ...... that is done by using the smaller prop and letting it turn up with a light load.

Important though.... do not just try using a stock 8x6. Hub is not strong enough.... cut down a bigger prop.
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Old 03-20-2011, 12:37 PM
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Default RE: Jett Stream muffler question


ORIGINAL: bob27s

That should work ok for you...... see how it works.

What I might suggest while waiting for a thaw ....... is if possible, put that engine on a test stand. Take and old prop (10x6, 9x6, what ever in that range) cut it down to 7.5'' diameter and balance it. Run the TT46 on the test stand with that prop start it a bit rich, and take it up to 16,500 with it still being slightly rich. Get a 3-4 tanks on it like that - occasionally lean it out to 17,000 (no higher for very long). After that... put your 10x5 back on... see how it performs.

Reason I suggest this ....... is your engine seems a bit down on rpm. A stock TT40pro with stock muffler and a 9x6 will turn 16,500 when properly broken in. That seems to be where its power band is. With a Jett stream on it we can typically go up to a 9x7 and keep that 16,500 rpm mark (ground rpm). The TT46 typically performs about 500 rpm higher. The main thing is breaking in the engine so it wants to run at 16,000+ ...... that is done by using the smaller prop and letting it turn up with a light load.

Important though.... do not just try using a stock 8x6. Hub is not strong enough.... cut down a bigger prop.
I've ran it a few times on the 9x7 prop with the highest reading being 16,500rpm. Here's a video of it running the best on the 9x7
http://s153.photobucket.com/albums/s...t=MVI_0010.mp4
Is this prop sufficient or should I still cut another prop down? I have some junk Master Airscrew props I wont do much with - I have 10x6, and a 10x8 I wouldn't mind cutting up. I won't cut up my APC props.

This engine is probably at the 2-3 quart range so probably still has some time left before it could be completely broke in. I'm not sure if its the way they came or not, but when new (glow plug out) the pinch at the top of the cylinder wasnt real tight like I've experienced with car engines in the past. It is at least 10 years old, and just sat in a box never being run until I got it.

Did you mean 9x6 at the end of your post or 8x6?
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Old 04-07-2011, 09:41 AM
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Default RE: Jett Stream muffler question

Hey that looks good........

The 9x6 or 9x7 should work best.

Look for that 16,000 rpm target - 500 either way - and you are getting the most out of the engine. It likely does unload slightly once moving.

I noted do not use a stock 8x6 prop. A 9x6 is usually ok.
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Old 04-07-2011, 03:49 PM
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Default RE: Jett Stream muffler question

I have ran it 3 times with a 10x6 cut down to 7.5" like you recommended, running it at around 16,500rpm with spurts at 17,000rpm. I put my 10x5 back on for a run and got 15,850rpm now. I'll try running on the cut prop for 2 more tanks and try the 10x5 again. I think it will hit 16,000 on the 10x5 with a little more finesse. With this 300rpm increase over my original runs I would think it's close to 17,000rpm on the 9x7. Time will tell.

I'm hoping to run the 10" props for more thrust, but I'll have to do what the motor wants to do.
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Old 05-01-2011, 06:14 PM
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Default RE: Jett Stream muffler question

yep... just run it. Don't get it lean, and just get time on it. They only get stronger
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Old 04-28-2012, 07:40 AM
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Default RE: Jett Stream muffler question

If no ones tried matching the ports how can you say it doesnt matter? I notice a huge difference in the port sizes from the muffler to my Thunder Tiger36.I guess the question is will it run any worse if the muffler is ground out to match?
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Old 05-01-2012, 05:45 AM
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Default RE: Jett Stream muffler question


ORIGINAL: pencon

If no ones tried matching the ports how can you say it doesnt matter? I notice a huge difference in the port sizes from the muffler to my Thunder Tiger36.I guess the question is will it run any worse if the muffler is ground out to match?
We have tried experiments, and others on their own have opened the ports too.

It will not typically run worse, no. So no harm experimenting. But doing so typically does not increase performance.
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