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Difference between OS 46 fx, and fxi?

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Difference between OS 46 fx, and fxi?

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Old 10-02-2008, 10:58 AM
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brett65
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Default Difference between OS 46 fx, and fxi?

My new decathlon has a 3 Flight OS 46 fxi in it, and it seems to run very strong. I had heard about the fx, which was replaced by the ax, but what is the fxi?
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Old 10-02-2008, 11:04 AM
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Default RE: Difference between OS 46 fx, and fxi?

Brett,
The OS 46 FXI was/is the engine that is sold with the Hobbico Nexstar RTF package. To my knowledge this is the only place that the FXI is used. You can't "buy" the FXI by itself. I had one for a bit and gave it away to two brothers that needed an engine. They use it every weekend and as far as I can see it runs and performs just like the 46 FX. I might be wrong, but I think that the "FXI" is just a name change done to make the Nexstar RTF package to "look" more impressive. It's just an OS 46 FX with a fancier name on it!!!!

Ken
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Old 10-02-2008, 11:04 AM
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Default RE: Difference between OS 46 fx, and fxi?

I believe that the FXI has limiters on the needle valve adjustments
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Old 10-02-2008, 11:37 AM
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Default RE: Difference between OS 46 fx, and fxi?

The engine looks like it just came out of the box, so I don't know if he pulled it out of a nexstar or what. I don't think he would have cleaned it up since it was in the cowl, but it was screaming with a 11x6 prop, so I don't think I'll be disappointed with it.
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Old 10-02-2008, 12:36 PM
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Default RE: Difference between OS 46 fx, and fxi?


ORIGINAL: brett65

The engine looks like it just came out of the box, so I don't know if he pulled it out of a nexstar or what. I don't think he would have cleaned it up since it was in the cowl, but it was screaming with a 11x6 prop, so I don't think I'll be disappointed with it.
This is typical performance for a .46 FX or FXi... They are the same except for the differences Ken already mentioned
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Old 10-02-2008, 02:04 PM
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Default RE: Difference between OS 46 fx, and fxi?

I had heard that the FXi designation was used to differentiate the later engines from the early .46 FX engines that were prone to peeling liners. The rumor mill said that the FXi engines were made with an improved plating process that kept the nickel where it was supposed to be.

I own both .46 FX and .46 FXi engines and find them identically outstanding in terms of performance and reliability.
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Old 10-02-2008, 07:35 PM
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Default RE: Difference between OS 46 fx, and fxi?

The way I heard the diff. to be between the .46FX and the .46FXI, is that the "I" in FXI meant that it was already "run in" and required no run in before flying, thus making the NexSTAR truly RTF. I may be wrong but that is what I heard. I have the FXI, FX and AX and they all seem to run the same.

Cheers

Curt
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Old 10-02-2008, 10:13 PM
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Default RE: Difference between OS 46 fx, and fxi?

You can go to the manufactures forum and ask Bax but I believe the only difference besides cosmetic is that the FXi has slightly lower compression. I have not noticed any less power on the ones I have personally used. They only came on the trainer plane.
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Old 10-02-2008, 10:39 PM
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Default RE: Difference between OS 46 fx, and fxi?

. . and here I figured the "i" was for injected, like it was/is the the automotive world!! <kidding>

Jack
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Old 10-02-2008, 10:44 PM
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Default RE: Difference between OS 46 fx, and fxi?


ORIGINAL: jib

. . and here I figured the "i" was for injected, like it was/is the the automotive world!! <kidding>

Jack
I wish, that would be the shiznit!
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Old 10-03-2008, 08:27 AM
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Default RE: Difference between OS 46 fx, and fxi?


ORIGINAL: Sourkraut

The way I heard the diff. to be between the .46FX and the .46FXI, is that the "I" in FXI meant that it was already "run in" and required no run in before flying, thus making the NexSTAR truly RTF. I may be wrong but that is what I heard. I have the FXI, FX and AX and they all seem to run the same.

Cheers

Curt
They're NOT run in. Like most other engines the carbs are pre-set at the factory to approx starting points before shipment. They still require the same typical minimum break-in proceedure as any other OS non-ringed 2-stroke.
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Old 10-03-2008, 09:25 AM
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Default RE: Difference between OS 46 fx, and fxi?


ORIGINAL: MinnFlyer

I believe that the FXI has limiters on the needle valve adjustments
No limiters on the needles with the .46 FXi. Only Evolution thinks their customers are too dumb to tune an engine.
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Old 10-03-2008, 09:31 AM
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Default RE: Difference between OS 46 fx, and fxi?

I remembered one other difference. It's been awhile since I had the FXI in my hand, so Ed correct me if I'm wrong, but didn't the FXI have a separate metal mount for the remote needle valve?? If so this differs from the FX which had the remote needle valve cast as part of the engine backplate. IMHO this was one of the only drawbacks to the FX engines. The reason is that if/when you were in a crash you can almost count on that mount breaking away, and they you have to spend $15 for a new backplate!! [:@] OS has now since gone away from that with the AX engines using a metal bracket that bolts on to mount the remote needle valve.

Just a little food for thought.

Ken
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Old 10-03-2008, 09:55 AM
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Default RE: Difference between OS 46 fx, and fxi?

O.S. made a change to the FX line during the life of its production. Later FX series engines used the same kind of seperate bracket that the FXi did.

The remote needle valve bracket that was integrated to the backplate had another problem besides being expensive to replace. Because the bracket was integrated with the backplate, it acted as a heat sink and transferred heat to the high speed needle after the engine warmed up. The backplate and remote needle bracket were redesigned more to prevent fuel vaporizing, reducing repair costs was simply an additional benefit.

I believe I read this explanation in a Glow Engines forum post, and it was a reply from BAX if I recall, so I'm confident that this is correct.
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Old 10-03-2008, 11:17 PM
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Default RE: Difference between OS 46 fx, and fxi?

[/quote]
They're NOT run in. Like most other engines the carbs are pre-set at the factory to approx starting points before shipment. They still require the same typical minimum break-in proceedure as any other OS non-ringed 2-stroke.
[/quote]

That was one of the selling points when I bought mine 4 years ago.... it was supposed to be run and broke in at the factory thus requiring no break-in before flying!!! Heck, I fueled mine up and flew it right out of the box, it ran great then and is still running great today. I also don't recall any limiters on mine either.

Curt
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Old 02-28-2019, 09:09 PM
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Default

Actually there are a few differences in the engine parts. Starting with the most obvious is they utilize different heads (The FXi Head is radius at the back), also the backplate are different. The crankshafts also have different part numbers, although the piston/cylinder set share the exact same part number on each engine. If you pull up the manual parts breakdown of each engine you can make a side by side comparison and you will note the different part numbers.
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