_Tommy D

My Feedback: (20)

Hey Guys

I contacted Performance Specialties regarding a Ultrathrust muffler for a OS 55AX. I'm told they are no longer in production. Does anyone have a similar product they could suggest? Looking to pick up a few RPM without a TANK <weight> of a muffler hanging off the nose.

Thanks!

Tommy D

pitstop000

My Feedback: (26)

Hear you go.
http://www.jettengineering.com/accy/jettstream.html

BiggerDanno

I just bought one at Jett two weeks ago.

_Tommy D

My Feedback: (20)

Thanks Guys

I was leaning towards the Ultrathrust one vs Jett for weight savings.....

What can you do.

Tommy D

BiggerDanno

I thought Ultra-thrust and Jett-stream were the same. Maybe not?

airraptor

My Feedback: (66)

lol they are the same and both copied the old super tiger mufflers or so i was told.

Go with the jett muffler very strong on the 55. if you have the ability to raise the exhaust timing then do that too. 170-175 for the 11x7 prop

zero-cool

how do you raise the exhaust timing?and what is the rpm gain?

_Tommy D

My Feedback: (20)

FWIW I found the mufflers I was looking for. If anyone needs one please PM me.

I would also be interested in any "speed secrets" for the 55AX <aside from replacing the bearings with a decent set>.

Thanks!

airraptor

My Feedback: (66)

i already told you and the 55 doesnt like to turn high rpm. they will blow up. all of ours after about 125 flights blow the cylinder or head off. they turn a 11x7 at 14,700-15,200

_Tommy D

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I'm not sure if that was aimed at me or not. If so I don't recall being told that the 55 is not a "rev-er"... is that a word even? =)

Literally blow the head off? That I would love to see! Seriously I mean blow the head off?!?

I was thinking 10x8 myself.

freakingfast

My Feedback: (3)

No, it wont blow apart if you take it to 20K a few times.The bearings may go first after a while. There's just no power up there, so why go there. You want speed out of it, just put more pitch on a prop and make use of power at lower rpm.
After market tuned mufflers work great on it. You didn't mention what plane it's going on, that can help us narrow the prop pick for you.

More info here, read through it all as the performance search evolves : http://www.rcuniverse.com/forum/m_5043356/tm.htm

_Tommy D

My Feedback: (20)

Sig Kougar

Just like this one <except this one has a 46AX on it> I know big frontal area, FAT wing, not exactly a speed plane. But a fine sport aircraft!

freakingfast

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That's fine plane.
11X7 Master Airscrew S-2 series(type) or 11X8 cut down to10.75X8. APC 10X9 may be a winner too, a 10X10 may be a bit much for that plane but it works well on a Quickie 40. These props are considering after market TUNED muffler or exhaust.

You may already know it, but the black Macs muffler pictured, does little for performance gain.

_Tommy D

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Thanks for the Advice. The "fake pipe" =) was added to help get a decent CG. Model is now tail heavy... go figure! As a bonus the model is fairly quiet. I say Bonus as I fly at a field dominated by electrics. A tuned pipe model is pushing it's luck there!

I'm going to compare <tach> the Ultra thrust against the Macs. Really hope to see a few more RPM from the UT.

Photo of Kougar II thats getting the 55AX. It was a STEAL at Toledo!

A6TEXAN

is this the correct pipe for the 55 ?

A6TEXAN

or would this one be better ?

http://www.horizonhobby.com/Products...x?ProdID=EVOM1

airraptor

My Feedback: (66)

i didnt say it would blow the head of it if it went to 20,000 lol the power we get out of them over time the cylinder or hear will come (blow) off of the engine. we had it happen to three of the 55's and twice on the 95 ax. we tried to get the 55's to turn high rpm and they dont really gain that much. the 10x10 at around 15,000.

for that couger you will need a 11x7 prop any higher pitch and will be slower with the gear hanging down. there were two at our field with the modded 55's they did about 120-125

cmircman

My Feedback: (10)

hmmm thats funnny my 55ax loves the jett muffler with a 10x8. As for the jett muffler being heavier than the ultrathrust I doubt it but it could be. I dont have a ultrathrust muffler for that size but i can tell you my 36's like the jett better and the jett is a couple of ounces lighter. maybe i will try that 11x7 later.

airraptor

My Feedback: (66)

I say the 11x7 on the kouger because of the tri gear our on the airstream. The 11 inch prop provides at bit more thrust over the ten inch props.

Iflyglow

My Feedback: (79)

The Blue Evo version is pretty much identical to the Jett Stream TT40, except for it is very slightly detuned and cheaper.

_Tommy D

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Guys

Got my Ultrathrust muffler Monday. It's been a long time since I have seen one, but the pipe inlet looks a lot smaller then the head exit. On a automobile head <4 stroke> this would be a huge no-no. However it works on 2 stroke???

ChrisAttebery

My Feedback: (15)

Yep, it will work just fine. If you're really worried about it you can carefully smooth the opening on the pipe so that it has a transition to the motor's exhust port.

_Tommy D

My Feedback: (20)

So if I "gasket/port match" it I will not ruin anything?

BiggerDanno

You will be removing backpressure, which the pipe is obviously designed to work with.

I spoke to Dub about this, he stated that the only reason for the large opening on the engine was weight reduction, not performance.

ChrisAttebery

My Feedback: (15)

Backpressure is controlled by the outlet. All you are doing is reducing turbulence in the system. You will probably not notice a huge difference, but it may yield a couple hundred rpm.

If it wasn't wirth doing then Jett and Nelson would save the weight and cost of the extra aluminum to port match their engines.