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JBA .56

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Old 12-25-2007, 07:27 PM
  #1
Ed_Moorman
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Default JBA .56

JBA .56, new, during break-in on my test bench. Rpm reading taken during the 5th tank through the engine. This engine belongs to "bigedmustafa" of Omaha, Nebraska. I am breaking it in for him and taking readings.

Fuel: Omaga 10% nitro, castor blend.
Glow plug: K&B non idle bar.
Prop: APC 11-6.
rpm: 12,800 (bouncing between 12,750 & 12,850 with an occasional jump to 12,900.)

Five tanks, five 1-flip starts. Very nice running engine so far.
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Old 12-28-2007, 06:51 PM
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Default RE: JBA .56

Got a chance to run the JBA some more today. Here's what I got.
Temp low to middle 60s
Humidity was high
Fuel Omega 10% nitro, castor blend
Plug: K&B RC
Tach-Tower cheapie

Prop Muffler Jett tuned muffler
11-6APC 12,800 13,800
11-6MA 13,100 13,800
11-7APC 12,400 12,600
11-8RevUp 11,300
12-6MA 11,600 12,000
12-7Zinger 10,200
12-7APC 10,800
12.25-3.75 13,000 13,900

Here's what I previously got on my OS .55AX
11-6 12,800 14,500
11-7 12,200 13,700
12.25-3.75 14,500 (no muffled rpm)

Actually, the JBA .56 looks really good for the price, especially with a muffler. I would say an 11-7 or 12-6 would be a good sport prop. Use the 12.25-3.75 for 3D and fun fly stuff. That's what I run on the OS 55 and plan to use on the JBA.

Here are some readings I took several years ago when I bought my first OS .46AX. They were only on the APC 12.25-3.75 3D prop. The fuel, temperature and humidity were the same.
OS .46AX 12,500
OS .46FX (old engine) 11,400
TT .46Pro (old engine) 11,500
Magnum .52XLS 12,800

The JBA .56 turns higher than any of these engines. The TT .46Pro will probably be better on a small prop (10-6 or 9-7) but probably wouldn't turn the larger props nearly as well, 11-7 or 12-6.

The JBA .56 seems to be more conservatively ported and timed compared to the OS .55. It doesn't respond to the Jett-Stream tuned muffler as well. You nominally need about 13,500 for the Jett to work. You can see that the props, 11-6APC & 12.25-3.75, that were close to 13,000 got a pretty large boost. Bottom line on the tuned muffler is I don't think the Jett is worth it for the JBA. With the OS, I gained 1700 on the 11-6 and 1500 on the 11-7 and that is a significant boost.

Bottom line on the engine: I'll have to fly it to see how it runs in the air, but from my initial testing and using the stock muffler, it is roughly the equivalent of the OS .55AX for a lot less money.

Ed
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Old 01-12-2008, 01:31 PM
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Default RE: JBA .56

Just for grins, I ran the JBA 56 with its muffler, a Tower .46 muffler and the PowerBox from the OS .55AX. Interesting results.

Prop APC 12.25x3.75

JBA muffler 12,700
Tower muffler 12,300
OS .55AX PowerBox 12,300

The only other thing is the muffler weight
JBA muffler 5.5 oz
Tower muffler 3.8 oz
PowerBox 4.2 oz

The JBA muffler is pretty heavy.

No, I haven't tried it on the OS .55AX, yet.
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