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  1. #1

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    Evolution 1.00 vs OS 91 FX

    Anyone have info on the Evolution 1.00 ? Particularly compared to the OS 91 FX ?
    Curious about this engine, considering putting it on a Excelleron as a backup plane for Intermediate.
    My primary plane is a Prophecy with a Webra 1.45 and Macs pipe, the Excelleron would be used over the winter while I am cleaning up the Prophecy after a season of use and abuse.

  2. #2
    MTK's Avatar
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    RE: Evolution 1.00 vs OS 91 FX

    The smaller Evos work well. Don't know about the 100 but do know that the OS91 is an excellent engine. You won't go wrong with his engine and the appropriate Macs pipe. Excelleron-OS91 is a fine combo

    MattK
    ORIGINAL: rcpaulrc

    Anyone have info on the Evolution 1.00 ? Particularly compared to the OS 91 FX ?
    Curious about this engine, considering putting it on a Excelleron as a backup plane for Intermediate.
    My primary plane is a Prophecy with a Webra 1.45 and Macs pipe, the Excelleron would be used over the winter while I am cleaning up the Prophecy after a season of use and abuse.
    Regards,
    MattK
    (Rcmaster199@aol.com)

  3. #3
    RC_Pattern_Flyer's Avatar
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    RE: Evolution 1.00 vs OS 91 FX

    Hey paul, Chuck here. I would go with the 91 on a pipe. The evolution is a great motor but it is not designed to make horsepower, just run strong and consistent for those who are new to larger engines. Stick with os and i think you will be a happier man.
    Mark Hunt Designs

  4. #4

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    RE: Evolution 1.00 vs OS 91 FX

    I'm running an OS .91 FX with an ES Composite 2C140XL80. 8900 RPM top end with 15% S&W, type F plug, APC pattern 15x10. It's a new setup for me, still working a few minor rough spots off the throttle transition, but it's running well. Not sure what the weights are for the EVO, but the ES pipe is only 3 oz, the OS header isn't much either, forgot to weigh it, but it has to be a good weight savings and probably much quieter than an EVO with a stock muffler.
    Ed Alt
    Tech-Aero Designs LLC

  5. #5
    Moderator blw's Avatar
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    RE: Evolution 1.00 vs OS 91 FX

    I'm not so sure about Evos being for guys new to larger engines, or the comment about not being made for horsepower. I have two of them and they are very powerful engines. I've owned a .46FX and the .46NT. I would put the NT up against any FX. The idea that Evos are for new guys is probably due to the limiters on the needle valves. They aren't a bad idea and are removable. I found that the NT low speed needle valve was far easier to tune and fly than the FX. Also, the NT tolerated out of tune conditions better than the FX. The FX crankcase loaded up worse than the NT.

    Evolutions are well made engines. They have one thing that OS doesn't- chrome liners. I'm not sure I would get another OS if a comparable Evolution were available. They cost about right (cheaper than OS), seem more powerful, and should last longer.
    The ultimate responsibility of pilots is to fulfill the dreams of the countless millions who can only stare skyward...and wish.

    "It's a new day for Auburn" - Gus Malzahn

  6. #6

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    RE: Evolution 1.00 vs OS 91 FX

    I will never buy an OS 91 Fx again. [:'(] I had 2, and they are junk. I do not know about the EVO 1.00 . But I do have an EVO 61 NT and I will put it up against OS 61 FX anytime.
    Old Myths Die Hard

  7. #7

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    RE: Evolution 1.00 vs OS 91 FX

    barber 701,
    What problems are you having with the OS 91 FX. I had one of those this spring and was not happy with it. Problems with muffler pressure being too high with an inverted installation caused problems, and I couldn't throw a prop with more load than a 13 x 8.
    Just curious.
    Paul

  8. #8

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    RE: Evolution 1.00 vs OS 91 FX

    The 91FX is a nice running engine with good power/weight. People often complain when they will not swing an 18" prop very well or when it goes lean with the tank mounted 18" from the engine. It has a big carb that does not pull fuel very well unless the rpm is way up, and it needs a pipe for good power with the larger props. In fact a piped 60 is simply more powerful than any muffled 90. The most powerful and consistant running 91FXs I have seen are using a pump and a pipe.

  9. #9

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    RE: Evolution 1.00 vs OS 91 FX

    Kweasel,
    You are correct about the 91FX - Nat Penton used to use one with a pump, pipe, 30% heli fuel and an extra head shim. It ran great, but, this is not a case of take it out of the box and run it. From my point of view it is a difficult engine. I think (hope since I have never ran one) that the Evo 100 NT is a lot friendlier. Usually the 91 FX is used on a Sportsman entry level plane - pilots in that class need a user friendly engine. Just my opinion. If I compare the results I had with the 91 fX on a Quest with the Webra 145 on my Prophecy - the Webra comes out light years ahead. It is not the most user friendly engine but once you get used to it it is very consistent.
    Thanks,
    Paul

  10. #10

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    RE: Evolution 1.00 vs OS 91 FX

    I've run two .91FX engines on my CAModels WIdebody. I found the engine to be quite user friendly. Mine was mounted so the muffler/header pointed down the middle of the bottom of the fuselage. If the engine flooded then it was a BEAR to start. DUmp all the fuel out of it (pull the plug and turn it over until 'dry') and try to restart. I ran an APC 14x8 with just the stock muffler and an APC 13x10 with a pipe; 10% fuel.
    Now for my 'beef'. The engine just doesn't seem to hold up. Specifically, the piston/ring fit. The engine would lose compression until it could not be started. About 70 flights with the pipe; about 140 flights with just the muffler. I don't run the engines lean or hot - the exhaust residue is always clear. I was VERY disappointed with the longevity of these engines. All other parts seem fine (bearings, rod, etc.); so I'm considering sending them back for new rings (and possibly liners and meybe even pistons). The piston/liner/ring assemblies don't have any scratches (from dirt or whatever being run through the engine).
    I've been flying R/C since 1969 and average about 500 flights per year. I've run lots of rear exhaust pattern engines (Bully 1.20LS with 1100 flights and ALL original parts) as well as side exhaust engines and except for my Enya .45s from 30 years ago never had an engine with such poor longevity (the ENyas' had all aluminum connecting rods with NO bronze bushings at either end - I couldn't get more than 30-40 flights from a rod).
    Sorry to ramble on, but I've never owned an OS I didn't like...until now.
    Happy Flying,
    Will B.

  11. #11

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    RE: Evolution 1.00 vs OS 91 FX

    hay guys this month is one year in this hobby for me so i still have lots to learn.i have a f90 with my second evo 100.i had the evo 46 in my trainer and loved it.but the first evo 100 i just sent back to horizon.i could run the engine on the ground,put it in the air,dead stick.then i could not get it to restart so i took a temp reading on the head at the glow plug and was hitting temps around 400 deg.the second one is installed with three flights and so far so good.i havent tried measured the temp on the new one yet but i will do so for a comparison.horizon had no info on temp readings,so im not sure if the problem was from overheating or something else.im currently running a 15x4 with 15% cool power and would like to run a 16x4 but not sure the evo could handle it.the plane flies good but vertical takes everything that engines got,so hovering is out of the question at low altitudes at this point.i would appreciate any and all info on this engine,fuels ,props,anything

  12. #12

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    RE: Evolution 1.00 vs OS 91 FX

    rcpaulrc
    My 91s lay on their side. The first one the chrome came out of the sleeve. Neither one would idle. They both vibrated so bad that they vibrated their mufflers off in mid air. I tried new fuel tanks, fuel tubing, spinners, propellers. And they still would not run. The biggest propeller that it would kinda run with was a 13/7. Both of these had the plastic high speed needle valve. I have been told that none of these are even good enough to be a trot line sinker. The old ones with the metal needle valve housing seemed to work okay.
    Old Myths Die Hard

  13. #13
    Moderator CGRetired's Avatar
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    RE: Evolution 1.00 vs OS 91 FX

    I have a two month old Excelleron 90 with the EVO 100 installed. I have had some problems with it from idle to mid-range, seems to want to quit on me. Mid range to full throttle, has great performance.

    But, as I fly it and put some time on the engine, it seems to run better, however, with the outside temperature hovering around 40 degrees F, perhaps that's a part of the problem.

    I also have a lot of fuel running out of the carb with the engine not running. Since I am fairly new to the hobby and am just starting out with the Sportsman level pattern, I am not totally educated on cause and effect of such problems.

    It is also tough to start when it is cold like that. But, again, that may go away after it warms up a tad bit, I don't know. I know that I probably need a starter motor with more torque or a better/higher cranking amperage battery.

    BTW, running it with an OS-F plug, S&W 15% nitro.

    As for power, well, it certainly pulls that Excelleron 90 around nicely, but again, with this being my first 90 sized plane, I don't know what is good or what is not so good.

    If any of you have any ideas about the fuel out of the carb (the engine is mounted inverted), please let me know. I am really open for any suggestions you guys can help me with.

    DS.
    Skylark 70 - OS .75 AX; Excelleron 90 - OS 1.20 AX; Venus II - OS 1.20 AX; And, I still fly my trainer, Hanger 9 Alpha - OS .46 FX! Some electrics. Airtronics RD8000 - Spektrum DX7 - DX6i. AMA 705964.
    Semper Paratus!

  14. #14

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    RE: Evolution 1.00 vs OS 91 FX

    DS,

    Fuel running out of the carb is generally due to siphoning from the tank. The carb is below tank level. You shut off the engine and the line to the tank is full of fuel and starts downhill. I've seen a tank get emptied completely more than once. Some put a tee in the line with a fuel dot at the high point then unplug it after flying. Some use a hemostat on the line if you can get to it.

    Sometimes inverted engines are hard to start because all of the oil in the cylinder pools right on top of the glow plug.

  15. #15

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    RE: Evolution 1.00 vs OS 91 FX

    with the engine inverted (180 degrees) starting is always a problem on a two stroke (four stroke no problem). I suppose you have the tank close behind the firewall. Make sure the tank is centered versus the carb (usually it is suggested to mount it centerline somewhat below the carb, but you want it to fly well inverted as well). What I developed now as SOP is:
    1. I have made a mount so I can start the plane inverted
    2. after fuelling up the first time, I unscrew the plug and give a 5 second burst with the starter. Look the other way, because there will be a lot of fuel coming out!
    3. I put in the plug again, prime the engine normally, and after connecting the wire to the plug, handstart the engine by flipping the prop while wearing a glove (I don't like a chickenstick, since it will damage the prop). It always starts after one or two flips. After the flight, I leave the carb in the closed (switched off) position, to prevent fuel siphoning out.
    4. after that, the next flights I don't need to remove the plug again, I just fuel, prime, connect, flip and it starts right away, no sweat.
    5. I prefer not to use the starter, it should not be necessary, you either damage something inside the engine, or your spinner or something will come off eventually. If it doesn't start, something is wrong! Better to fix it then to force it. I found .25 or .46 engines more difficult to start (and do use a starter on them), a 91 or 160 can always be started by flipping and on our field everybody does.
    Temperatures here are around 30-35F (0-4 degrees Celcius) now.

    I fly an OS-91FX with pipe on 18% synthetic oil (Klotz) with 5% nitro. Don't hear any complaints about the 91FX around here, always run fine. Be aware that here (the Netherlands) nitro is quite expensive, so in general people fly with 1-10% nitro.

    I added a picture of how it sits when starting; build this very roughly in 20 minutes with a piece of garden hose as liner; works fine
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Club Saito member #371

  16. #16
    Moderator CGRetired's Avatar
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    RE: Evolution 1.00 vs OS 91 FX

    Thanks for the info. If it works like that in the Neatherlands then it ought to work here where the temp is more moderate.

    I was told to loop the fuel like, large loop so that on end of the fuel line is above the tank level then secure it somehow to the firewall so that it does not move. This is supposed to prevent the fuel from running out. I had been using a pair of hemostats to clamp off the fuel line when not in use but got frowned upon by the club pro's.. dunno why..ha.

    Ok.. will try your suggestions.

    Thanks again.. and will put together some sort of mounting rig like you have.... looks like it ought to work!

    DS.
    Skylark 70 - OS .75 AX; Excelleron 90 - OS 1.20 AX; Venus II - OS 1.20 AX; And, I still fly my trainer, Hanger 9 Alpha - OS .46 FX! Some electrics. Airtronics RD8000 - Spektrum DX7 - DX6i. AMA 705964.
    Semper Paratus!

  17. #17

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    RE: Evolution 1.00 vs OS 91 FX

    good luck, let me know how it works out. Of course the flipping story is an optional, using the starter is just fine, but it should not be difficult to turn over the engine, and it should start after a second or two. It shouldn't be like drilling a hole in the wall! If using the starter, it is always a good idea to first turn over the engine by hand a few times, to make sure it is going around ordinarily, not too heavy.
    Cheers, Volkert
    Club Saito member #371

  18. #18

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    RE: Evolution 1.00 vs OS 91 FX

    I vote for the Supre Tigre 90 against both of these as it is a stump puller and I have found the ST carb to be quite user freindly!!! The OS I had was a bear to adjust, needed a pump to run well and never quite lived up to the power they promised. Now maybe the 91FX and the old os 108 carb....hmmmm...that might be an idea......
    power corrupts...
    absolute power corrupts absolutely

  19. #19

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    RE: Evolution 1.00 vs OS 91 FX

    oh, I don't know, usually you have to be a bit lucky as well. I fly Saito and OS-MAX, but that's basicly because they are good brand engines, and the local hobbyshops carry the parts if you need them. I don't buy any of the cheaper brands, but that's because I don't have time to fool around, the time I have available I'd like to use flying. There is nothing worse then spending an afternoon trying to get an engine running, cursing yourself why you did not spend the extra 20$ on a "good" engine (even when that has nothing to do with it....). My OS-91FX now runs 9800 rpm with an APC 14-8 on 5% nitro, and I am very happy with its performance on a 7lbs airplane. I found the idle setting too rich, but I did not mind this when running in. The engine now runs very sweet, so things went well I suppose.
    Club Saito member #371

  20. #20
    baronbrian's Avatar
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    RE: Evolution 1.00 vs OS 91 FX

    Not to bash evolution, But after spending a whole weekend trying to get a 1.00 running right on a buddies funtana 90, I am glad all my current glow engines are O.S.
    Contest Director for the AMA
    Grand Forks, North Dakota- Where time stands still but the air is always moving.

  21. #21
    Moderator CGRetired's Avatar
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    RE: Evolution 1.00 vs OS 91 FX

    EVO 100 NT on an Excelleron 90 Pattrn Plane.

    With all the info above, I headed out to the field today. The club 'experts' were all there. They looked over the tank installation and said that it was appropriate where it was. Next, there was comment about the fuel running out of the carb. No one seemed to be able to explain it. Not sure what that is all about.

    It started right up, no problem. However, if left at idle, it leaned out and quit running. One of the club Pro's, I'm pretty sure many of you know him or his name, Dave Lockhart, looked it over. He listened and adjusted and listened again. Once he thought he had it, well, at idle, it would still run, then appear to lean out, and quit. At one point, he said that it was ok from about mid range to full throttle and that maybe it just needs to be run, so I refueled and put it in the air. I ran a full tank through and finally headed for a final approach when it quit on final.

    I thought it may be out of fuel, but it still had a quarter or a tank or so. So, again, it quit at idle.

    I refueled and wanted to put it back in the air but when I would get it to the flight line, it would quit. So, finally, I decided to call it a day and defueled it.

    I noticed that one of the pull-pull cables for the rudder was broken (Sullivan Kevlar..what's that all about!!!). At least it didn't break in flight... or may have but I didn't notice it because the wind was pretty much calm and my approach and landing was pretty much down the centerline.

    I am getting ready to take that engine off and just wait until I can afford to pick up a new OS.. looking at the 91 or the new 1.20 AX. My original thoughts about buying the Evo 100 was not basically economic, I just wanted to get one and see how it performed. I had a .40 and still have it, and it still runs just great so I thought that the 1.00 would run just as nice. A friend has a pair of .36's on a Twinstar and his comments are 'Sweet'!!! But, in both cases, the engines are upright mounted, not inverted.

    Anyone comment on my engine problems?? I am definitely and obvioiusly frustrated.

    The Excelleron fly's so sweet and I love flying it, and am having a good time getting ready to compete in the Sportsman class this summer, however, without a reliable engine, all thoughs about competing are just that.. thoughts. One practice flight a day just won't cut it, ya know?

    DS.
    Skylark 70 - OS .75 AX; Excelleron 90 - OS 1.20 AX; Venus II - OS 1.20 AX; And, I still fly my trainer, Hanger 9 Alpha - OS .46 FX! Some electrics. Airtronics RD8000 - Spektrum DX7 - DX6i. AMA 705964.
    Semper Paratus!

  22. #22

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    RE: Evolution 1.00 vs OS 91 FX

    How do you know it leaned out at idle? I would let it idle for a bit then pinch the fuel line and see what happens. If it dies immediately, it is lean. If it runs for a while or speeds up a lot, it is rich. Is it mounted inverted? With your problems with fuel siphoning, you may be too rich on the low end. Perhaps a hotter plug would help.

  23. #23

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    RE: Evolution 1.00 vs OS 91 FX

    Have you considered using a Cline regulator (or Iron Bay ditto)? They do make the engine independent of the tank position(fore and aft, and in the vertical plane).
    A consistent engine is essential for pattern flying, more so than anything else, and it's surely significant that all
    modern-day setups use pumped fuel delivery of one kind or another.

  24. #24
    Moderator CGRetired's Avatar
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    RE: Evolution 1.00 vs OS 91 FX

    JVB: Yes, it's lean at idle. If I let it run a few seconds, it starts to surge then dies. I have a new OS-F plug installed. Yes, the engine is mounted inverted.

    F3A05, where do I get a cline regulator?
    Skylark 70 - OS .75 AX; Excelleron 90 - OS 1.20 AX; Venus II - OS 1.20 AX; And, I still fly my trainer, Hanger 9 Alpha - OS .46 FX! Some electrics. Airtronics RD8000 - Spektrum DX7 - DX6i. AMA 705964.
    Semper Paratus!

  25. #25

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    RE: Evolution 1.00 vs OS 91 FX

    F3A05, where do I get a cline regulator?

    They're in Ohio, I think.
    I just Googled billsroom.com and it all shows up there.
    Sorry that's a bit less than precise but my computer skills are limited.


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