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Jett. 90L muffler offset part help

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Old 07-27-2008, 01:20 PM
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Zman39
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Default Jett. 90L muffler offset part help

I have a Jett .90L with the red tuned muffler. I need the muffler to be just a touch higher to clear wing on Delta Vortex. I thought Jett made an offset spacer that gives a little rise but an email to them advised they are out until next week. Anyone know where else I can locate this part so I can get this plane flying?

Any help much appreciated

Z
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Old 08-04-2008, 09:09 PM
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Default RE: Jett. 90L muffler offset part help

Hi.....

Unfortunately Dub is the guy.... and he is on vacation. I just got back from vacation myself Dub will be back on Monday.

There is a "jog" adapter we have used in the past - looks like the adapter we use for the older bolt-on muffler engines like the YS45 and Rossi 45-53. I think Dub can make one that mounts Jett-to-Jett

The few folks I know who built the D-Vtx built in a pocket along the fuselage/leading edge to accomodate the muffler.
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Old 08-05-2008, 06:24 AM
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Default RE: Jett. 90L muffler offset part help

Thanks Bob,

I got to looking last night and OS makes a 1/2" mufler extension. Any idea if they are close in mounting bolt widths and 2) would half inch make performance suffer?

Thanks

Mike
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Old 08-05-2008, 02:37 PM
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Default RE: Jett. 90L muffler offset part help

OS bolt pattern is different.

Jett muffler bolt pattern matches ST90 bolt pattern if that helps in the short term.

Yes, it does affect performance adding spacers. Drops rpm a bit, but usually not too bad if its only 1/4-1/2" .
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Old 08-05-2008, 06:05 PM
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Default RE: Jett. 90L muffler offset part help

Okay, thanks Bob. I think I will just modify wing so it rest in normal position.

Thanks a bunch

Mike
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Old 10-10-2011, 12:44 PM
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Default RE: Jett. 90L muffler offset part help

Does jett make a spacer for the muffler? I have a jett 90L on an Ultra Sport I am building. Right now the exhaust sits directly 1/2 of an inch front of the leading edge of the wing. what fuel tank would you recommend? I bought a tetra fule tank that is way to long, it will not allow the wing to fully seat.

any help is greatly appreciated
josh
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Old 10-11-2011, 05:50 AM
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Default RE: Jett. 90L muffler offset part help

Hi Josh.. thanks for writing.

Yes, Dub has spacers. But 1/2" is a long distance.

I had the SJ-90L on my ultrasport for a while. Flew great, and I installed without any spacers. Required sanding/relieving some of the chin block on the lower front end. A few minutes with a dremel and all was good. exhaust diverter on the end, and no issues with the wing.

Configured with a standard Dubro fuel tank in that. Nothing special. The plane has a solid front end and tends to transfer energy well. Just make sure the tank is well padded. If you want to go with a bubble tank, I think Tetra makes a 14oz that would work pretty well. Remember, you get to use ALL of the fuel in a bubble tank. Regular tank has 5%-10% unusuable fuel.... 16oz tank only has 14oz of useable fuel in it before you start sucking air.

More to your question - What I would suggest is looking here
http://www.jettengineering.com/engines/sj90-new.html



The Toni muffler extention kit gives you two things..... extra distance, and a few degrees extra outward angle. This sounds like what you are looking for.

If this suits your installation, simply order "TONI EXTENSTION SET, SJ90L" either by phone or use the on-line order form.

The system ends up being slightly longer, so your target rpm is more in the 13,800 14,000 range. Nothing lost really, tradeing rpm for torque. 11x8 and 11x9 will work great.

I hope this is helpful
Bob
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Old 10-11-2011, 07:37 AM
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Default RE: Jett. 90L muffler offset part help

So you think a 1/2 inch is far away that the covering will not melt off of the leading edge of the wing? Or do you think I need an exhaust diverter? the biggest bubble tank jett has is 12ounces I think, I am looking a for a little longer flight time. Originally I was going to use a tetra 14oz which would give me around 5 minutes of flight time wide open, but the tank dimentions are all wrong for that tank-its way to long. tetra makes a 16oz tank that is much shorter, i think i will try that 1

thanks
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Old 10-11-2011, 12:12 PM
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Default RE: Jett. 90L muffler offset part help

What ever tank you are comfortable will work fine. A regular tank will work ok, just make sure to pad it properly and that it does not touch the airframe.

With bubble tanks, you can use more than one tank. Run them in parallel. That might be an alternative. Quite a few people run the 6oz tanks paired up for some applications.

If you are flying at 100% throttle all of the time - yes, you will burn up about 2 oz per minute. Throttle back now and then in the turns - really makes a difference.

You may want to put the divert on there or just a short one to deflect downward. Alternative is simply wrapping a small piece of aluminium over the leading edge.

The Toni extention will give you a few degrees more angle away from the fuselage and the wing. Probably will miss and go below anyway.


http://www.rcuniverse.com/gallery/ga...6memid%3D30292

That is a photo of a standard SJ-90 with two 1/4" extensions added. Clears the bottom of the wing easily. Toni angled adapter will angle further downward
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