Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Ultrathrust muffler/OS91

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Old 08-01-2007, 09:04 AM
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ggroyal1
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Default Ultrathrust muffler/OS91

Installed new Ultrathrust muffler from Performance Specialties on OS91 in the GP Little Toni. Also installed a Cline regulator. Gained about two thousand RPM's and the temp is around 190F with APC 14x7 sport prop.(11,000RPM). Does anyone have this setup? Any suggestions?
Thanks,
George G. Royal
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Old 08-01-2007, 05:50 PM
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Flyboy Dave
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Default RE: Ultrathrust muffler/OS91

.....you are getting 11,000 RPM now with the Ultrathrust muffler ?
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Old 08-01-2007, 07:31 PM
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Default RE: Ultrathrust muffler/OS91

I run a 13/8 apc on a Shoestring with a G90. I don't recall the numbers but I know it's more than that with a pitts and at 5000ft
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Old 08-01-2007, 07:36 PM
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Default RE: Ultrathrust muffler/OS91

Hey Dave,
I have been trying to get the OS91 to really scream. I am using cool power 20% and now a 13/10. apc prop. Increased rpm to 12,000. Clocked the Little Toni at 119mph. Still learning about the HOT stuff. Never had a problem with the stock trainer planes. I read the RCU forum every night and try most of the suggestions from all the nice people that contribute to the forums. I also just got into gassers in the last six months and I might be approaching overload. Anyway thanks for your help over the last year and half.
George G. Royal
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Old 08-01-2007, 07:51 PM
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Flyboy Dave
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Default RE: Ultrathrust muffler/OS91

....you're welcome, George. [sm=thumbup.gif]

You are on the right track with the smaller diameter prop, with lots of pitch.

FBD.
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Old 08-03-2007, 09:58 AM
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Default RE: Ultrathrust muffler/OS91

You want the OS91FX turning around 12,500 - 13,000 rpm for best power

(remember, its an over-grown .60 size engine..... not a big-block .90)

Try a 12x8 or 12x9 ...... let that thing turn up.

also...
which ultra-thrust did you purchase? RPM version or the Torque version?

Bob
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Old 08-03-2007, 01:09 PM
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Default RE: Ultrathrust muffler/OS91

Hey Bob,
I am using the sport version(UTS4). I would really like the JETT 90 Little Toni setup. I have been looking at it for a couple of months and reading everything on the RCU. I guess to get the max mph, I will have to upgrade to the JETT. Right now it is running at 115 to 118 using the Bushnell radar gun and risking my life while my son aims the Little Toni at me.
George G. Royal
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Old 08-03-2007, 01:57 PM
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Default RE: Ultrathrust muffler/OS91

With the muffler extension set, a jett-stream or ultra-thrust muffler.... and a 12x8 prop...... that is about as fast as the Toni is going to go within 3-5 mph anyway.

If you have the sport version, you have to get the rpm up a bit. Try the 12x8 prop.

Its a big plane, lots of drag.
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Old 09-12-2007, 04:38 AM
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Default RE: Ultrathrust muffler/OS91

Im running a ST g90 with ultrathrust.

Only getting 12 000 rpm using a 12x8 APC.

????? Didnt see much of a change in rpm. Ising the sport UTS4 with adapter

Rob
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Old 09-12-2007, 05:17 AM
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Default RE: Ultrathrust muffler/OS91

Hey Robert,
Take a look at Jett.

http://www.jettengineering.com/
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Old 09-12-2007, 09:07 AM
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Default RE: Ultrathrust muffler/OS91


ORIGINAL: Robert Groves

Im running a ST g90 with ultrathrust.

Only getting 12 000 rpm using a 12x8 APC.

????? Didnt see much of a change in rpm. Ising the sport UTS4 with adapter

Rob
You have to prop to the muffler a bit.....

swap down to a 12x6 and see what happens..... comare stock muffler to the UT on a 12x6
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Old 09-12-2007, 09:40 AM
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Default RE: Ultrathrust muffler/OS91

Thanks Bob

I will be putting the stock muffler on and taking readings with 12x6, 12x8 APC, 12x8 13x6 MAS, then the same with the ultrathrust.
Then playing with castol fuel and an Os8 plug.

The other anomile that can be playing funny with me is the adaptor plate. UT no longer makes a size to fit the ST90, so an adaptor plate is needed. The one I made lines the pipe and exhaust perfectly, but is wider than both on the one side. Bob,could this be affecting the pipe performance? I am talking 5mm here

Thanks
Rob
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Old 09-12-2007, 09:55 AM
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Default RE: Ultrathrust muffler/OS91

Proably not a big effect.... on the misalignment and adapter.

The engine simply has to turn up a bit more to really utilize the muffler boost.

Your approach for before and after readings is good. Will keep an eye here.

Of note, the Jett 90L engines use the ST60/90 bolt spacing. Mufflers are actually (integrally, two sets of holes) adapted down to the OS bolt spacing.
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Old 09-12-2007, 10:13 AM
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Robert Groves
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Default RE: Ultrathrust muffler/OS91

thanks bob.

Ill do the test as soon as I can.

Believe it or not, just got a call from the LHS, my F16 is here, eventually after 4 mo nths wait. Shipping to South Africa took 8 weeks by ship, lol, not be requiring spares I hope,

Cheers for now

Rob
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Old 09-13-2007, 05:43 PM
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Default RE: Ultrathrust muffler/OS91

The Ultra Thrust Sport, long muffler, is set for a lower rpm. I have one and used it on an OS .91FX and also on a Magnum .91XLS. I ran a 14-6 APC and gained 1,000 rpm on 10% Omega. When I ordered mine, I spoke to Dave and told him I was running a big prop on a big plane and he recommended the long, Sport muffler which is tuned for around 12,000 rpm. He also had the shorter muffler for running a 12-8 prop at a higher rpm.
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