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Evo 61nx vs O.S. 65AX

Old 01-04-2011, 05:46 AM
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w8ye
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Default RE: Evo 61nx vs O.S. 65AX

The 60NX and 61NX situation has certainly created confusion?

An odd situation is that the 60NX actually has a slightly larger displacement than the 61NX

Old 01-04-2011, 06:44 AM
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blw
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Default RE: Evo 61nx vs O.S. 65AX

I have a friend who runs his BT Vortex with a 75AX. I don't anything about power, etc. It seems to run well.

I have a .36 too but I haven't run it yet. It looks to have had a couple of gallons run through it already. I think I paid $30 for it.
Old 01-04-2011, 01:21 PM
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Reson7
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Default RE: Evo 61nx vs O.S. 65AX

Its a shame Evolution doesn't have many engines, if only they had the variety that O.S. has.....
Old 01-26-2011, 08:03 AM
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Default RE: Evo 61nx vs O.S. 65AX

I have a 3+ yr old 55AX and a 75AX for almost 2 yrs. They're very reliable in starting and throttle transitioning. I have nothing against the EVO engines, in fact I almost bought one last week until I researched the new 65AX. May I mention that OS engines out number all other brands combined at my club with one exception - electrics. I still love the nitros though - with all the cumbersome logistics and expensive fuel.

One thing I haven't seen in this forum (or over looked ) is the weight factor. The 65AX weighs only 17.5 oz with muffler and runs 2 HP to boot!

I have been looking for another engine to replace the heavy 75 AX in my ultra sport 60. Like I said, almost went with the EVO, but it has a 46 size foot print and I need something to drop into a 60 sized mount. If I can afford to, I will spend the extra bucks for a scotts mac tuned muffler and lower the weight and increase HP. This is almost perfect!

I agree with the contentions about OS prices being so high, but they still exist as a big business. The change in weight may become a new policy due to the popularity of electrics - look at the Jett 60 XL... oooh if I only had the dough!

My biggest complaint about OS is their deletion of afore mentioned engines of past - why on earth did they discontinue the mighty 1.08? The return of the 25 FX is understandable, now let's see where this goes.
Old 01-26-2011, 12:57 PM
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Reson7
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Default RE: Evo 61nx vs O.S. 65AX

Well the EVO definitely weighs quite a lot more at 25.44oz vs. 19.4oz for the 75AX, plus thats 2.4 HP, I don't understand why EVO won't put out there output power?????? I also recently noticed they lowered the price of the EVO 61nx, it was $144.99, now its $119.99, $25 difference while the O.S. is $229.98, more than $100 for just a little more power, but still, seems as if the O.S. will definitely give more power and is less weight which is good since my plane is very nose heavy with the EVO.
I still have not decided what I'm going to do, but will most likely go for the O.S.
Old 01-26-2011, 01:45 PM
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Default RE: Evo 61nx vs O.S. 65AX

It wouldn't matter if they did post hp numbers. They are all fiction anyway when you find out how the arrived at whatever numbers they want. They don't apply to actually using the engine to fly any model.
Old 01-27-2011, 07:19 AM
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Default RE: Evo 61nx vs O.S. 65AX

Good point but not entirely fiction. If you don't believe in rated hp look at their rated RPM. Both OS engines I own are running approximately 200 - 300 RPM below advertised, both are well broke in and use smallest sized props recommended. Another club member likes using undersized props on his OS 55 AX, and runs 200 RPM over the recommended RPM range. Who's engine will out live the other? Mine - I hope!

I haven't tached the EVO at the club yet, but I'll bet it's also gonna be close to or match it's rated numbers.

My observations watching others at the club with glow engines have shown staunch diversity in brand preference that proves the phrase "to each - his own". If the predictability of aircraft performance is important, weight to rated RPM/power is equally important - such as pylon racers that are given a set of one brand and class of engine/fuel/prop. Usually all run very close and steady thereby putting everthing on the pilot's shoulders!

My point is that there is a science to actual brake hp for every kind engine, and it takes a lot of fine tuning to get its optimum when you're dealing with props and engines. Some fliers make this a religion, to me, well I'd rather spend my time having fun (not to say there's anything wrong with competition).

I have also seen with my own eyes anomalous differences of RPM in the small glow engines. I have a Magnum 15 that turns an 8 X 4 at 20,000+
THIS engine has out performed all other contenders - just had to brag, sorry.


Old 01-27-2011, 08:37 AM
  #83  
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Default RE: Evo 61nx vs O.S. 65AX

The OS .61 FX was close to last place in the MAN shootout almost a decade ago. I think Fox and Tower were at the top. Not because of power but poor performance. People are throwing about numbers that sound unrealistic to me. Or perhaps the number are with a pipe. The most powerful .61's without pipe could turn a 11x7 at about 14,000 RPM. with a 12-6 about 13,400 or so.
Old 01-27-2011, 09:36 AM
  #84  
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Default RE: Evo 61nx vs O.S. 65AX

They were discussing that MAN engine article way back in 2003 in this thread here: http://www.rcuniverse.com/forum/m_65.../tm.htm#658084
this looks like a reprint of the magazine article too:
http://findarticles.com/p/articles/m...5/ai_n9251269/

Now I know what I did wrong in checking RPMs on my engines a while back. I have been using 11x7 Zinger wood props, and they are harder on a engine to turn than a wimpy little APC 11x6 prop. I normally use 11x6 props on my Fox 45 and 50 engines and 11x7 and 11x8 props on my .60 engines. I remember getting around 12,500 RPMs with a 11x6 Master Airscrew prop on one of my venerable Fox 45 engines recently. But my .60 engines were all running around 11,000 rpms with a 11x7 Zinger prop. But my old Fox Hawk .60 did turn around 12,000 rpms with the 11x7 prop but it has been very well broken in though. I tried a cheapie ASP .61 and it was impressive in that it turned the 11x7 prop at around 12,300 rpms with the stock muffler too. I was only using 5% nitro Omega fuel too.
anyway I guess I should have under propped the engines to get these higher RPMs out of the engines.

In my opinion it will be next to impossible to duplicate any performance numbers someone pusblishes as you don't have their exact propeller that they used. You want all the engines to use the same propeller, as each propeller is a a little different from the next one. The same engine test stand as vibrations from the engines can rob them of power, so you want all the engines to have the same engine test stand too. Then the engines all have to use the same fuel. Then they all need to use the same glow plug (as variations from plug to plug exist, but with new engines you can contaminate and or blow out a plug prematurely too. Finally you have to have the same environmental conditions too, weather, temperature, humidity, barometric pressure. Factors like altitude can affect the results as well.
I also suspect some manufacturers of fudging or lying about their results. One can shave or sand down a propeller to make it a little more thin or shaped differently. Thus one could get the engine to turn most any RPMs that you want it to.



Old 01-27-2011, 09:38 AM
  #85  
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Default RE: Evo 61nx vs O.S. 65AX

Keep in mind that rpm numbers on the ground don't tell you much in regards to actual performance. You need onboard gear to tach the engines while in flight to have meaningful numbers once the prop and engine have reached an efficient state. Otherwise, static rpm doesn't tell much about real life performance.
Old 01-28-2011, 12:57 AM
  #86  
Kweasel
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Default RE: Evo 61nx vs O.S. 65AX

One engine that really impressed me was the ST75 because of its overall handling and power. The ST carb tends to run a little rich around half throttle, like they always have. Now when I need a sport 60 I pull a carb off one of my OS61s and use the 75. It makes more power with better fuel draw and is just as easy to run as my finest OS61.

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