Propworn

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This is a G38 running on Coleman Camp Fuel

Propworn

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This is a University of Windsor 14 ft span model designed for the SAE Aerodesign Competition. It's powered with a custom-built JETT motor. I was the advisor/pilot for the team. I believe the motor was designed as a long stroke for more torque to throw a bigger prop.

Propworn

My Feedback: (3)

This was the year I put on a heavy lift competition for anyone flying from my home field. The only restrictions were a total lifting surface wing and horizontal stab 1000 sq inches max and a bone stock OS .61. It weighed in at 7 lbs. Had spolerons for roll control and an extra large rudder. Lifted 20 something lbs of lead on a grass runway. Its the Blue one. Two finalists first group from Montreal then me.

Propworn

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None of these engines were running more than 11,000 static on the ground.

the Wasp

My Feedback: (1)

20 pounds is some weight for a model. what was the prop on your engine. was it the FX?

Jim

1QwkSport2.5r

We got off the subject a bit here. All I was trying to say is if you have a big prop on an engine and it will not settle in to a needle setting, your idle and WOT RPM are too low causing the low speed needle being seemingly ineffective and the high speed needle to become ultra sensitive. The OP was using a 10x8 on an OS .55AX. That is a good prop for that engine that should yield some good RPM. After a 30 minute break-in, it should take a good needle setting. It’s always better to err on the rich side rather than the lean side. Until it’s well settled (broken in), you will want it to be a bit fatter on top. Use the pinch test on the high speed @ WOT for a noticeable rise in RPM while maintaining clean running.

Propworn

My Feedback: (3)

Yes it was an older .61 new in the box if I remember correctly the prop was a 14X6 or 5 for more tractive effort on the ground. Larger foam wheels for less rolling resistance. Notice it nosed over on the first attempt to take off. That was because the CofG was right on the center of lift allowing the horizontal stab and elevator to be on the small side. This allowed more lifting area for the main wing but was a bit lacking in effort at low rolling speed. Second attempt started with lots of up elevator reducing it as ground speed picked up, rotating at the end of the runway with max gound speed.

The horizontal stab was also a lifting airfoil as I have found it to be more effective in low speed applications. The airfoil used was a selig1223.

Propworn

My Feedback: (3)

Its all good info and some can even be entertaining as well as informative. The op found the information that helped him solve his dilemma. As we can see from the differing answers there is more than one way to work through a problem. Unless you want some sort of acknowledgment that your method is the best and only way to achieve what is desired. Post what you want others should feel free to do the same. I have learned many things from the strangest sources on these forums from experts to raw beginners. No need for the forum police.

I for one have never bothered with the pinch test. For one most of my engines are shrouded in some sort of cowl making pinching the fuel line difficult or impossible. A tach or experienced ear works just fine along with a good eye on how the engine/aircraft is responding. If I can I try to tune and fly the first flights without the cowl. When I am satisfied I install the cowl without changing the settings on the engine and observe if the engine runs differently. If adding the cowl effects the engine to much I attempt to alter said cowl so it runs as close to the uncowled set up.

rcbence

Well guys I have a new issue that I didn't notice during my first flight because my mid-range was too rich and I dead sticked. So I thought everything was perfect as I leaned the low speed out and got the high speed right and ended up dead sticking this last weekend on my second flight. This time I found out because it was too lean just under quarter throttle. Luckily I barely landed the plane safely.

I have a video that I might add here that I'm sending to YouTube. Of course it's kind of difficult to go just by listening to it as someone could think everything is perfectly fine by listening to it.

On my radio there's the white throttle position lines of course as you move the throttle. The first white line above the idle line is the specific throttle area that has a problem. It looks to be just under a quarter throttle. This specific throttle position is leaner than the rest of the throttle range. That much is certain. When I tested it on the ground after the dead stick I found the engine ran extremely smooth and leaned out and sagged out and died. And smooth in a bad way for a two-stroke where it's running lean. Zero crackle or richness to it. I richened up the low speed enough to where it was on the edge but didn't die on the ground and ended up flying the rest of the time. But something's not right with the carburetor because this doesn't seem normal.

Further ground testing today shows me I cannot have the mid-range to be perfectly smooth and crisp without getting too lean in that one throttle position. I have to strike between the two extremes and then neither position is ideal. If I make that low throttle position rich enough to where I'm confident its slightly rich.... After a few seconds at half throttle and accelerating from there it'll cough and die from being too rich. I tested this multiple times. If I make my mid-range nice and crisp and with good throttle transition....... That low throttle position will be too lean and die. The only way I can keep it running is to split the difference. Neither side is ideal. The mid-range is a bit too rich and that low throttle position is on the very edge of lean.

I tried an A6 hot plug, and even an OS F plug with double washers. It did the exact same thing so I put back the OS 8 plug. I don't believe its anything else except the carburetor. But what is wrong if its the carburetor?

It might be true that a slightly bigger prop with more load masked the problem a tiny bit. The problem is still clearly there with an APC 11x7. It's clearly running way leaner at this liw throttle position than anywhere else. The air fuel ratio is definitely leaner and different than everywhere else.

My only guess is that it is the carburetor's fault. And this is very consistent. Does this sound normal for an OS carburetor and engine?

Once again it's 10% nitro 20% oil and the fuel is fresh and good. There's no leaks anywhere in the lines are all new and it'll run consistently all day long. Consistently with this problem that is with one throttle position that's leaner than the rest of the range.

Is this how this carburetor is? Is there something I can do myself to make that throttle position a little richer without screwing up everything else? I don't remember having this problem with my thunder tiger pro 46 which I haven't ran in a long time on another plane. I'm not sure if the carburetor will fit the OS 55 for diagnosis reasons? I have a spare used tt pro .46 in a box also I can steal the carb from.

This is pretty disappointing for an OS. This throttle position is what I would use quite a bit and I refuse to believe it's normal to use the carburetor is strictly an on and off carburetor. I'm constantly throttling back and using the throttle so I need my quarter throttle range for just cruising for a little bit and need it not to be too lean there.

As I move the throttle slightly above this range I can tell it instantly richens up some just by moving the throttle open a little more. It is specifically a specific throttle position that's leaner than everywhere else. A throttle position that I happen to use all the time.

Any ideas on this? I am able to tune the mid-range so it runs incredibly crisp and perfect. I'm also able to tune that low throttle position so it's perfect. But I cannot do both at the same time because the engine will die from either being too rich in one area or too lean in the other. I would call it barely flyable by splitting the difference and I don't like it. Any ideas on what I can do would be greatly appreciated. I'm not willing to try something like 20% nitro so everyone knows. I refuse to believe that it shouldn't run perfectly fine on 10% nitro as the manual states that's right in the middle of what it recommends. Unless this is normal for all OS carbs on this engine? It looks like it uses the exact same part numbers as the OS 46. Looks to be using the same control mixture valve and other parts.

If I have a little booger in the carburetor, boy is it perfectly consistent. Planning to fly this weekend again so I might just have to take it apart. I suspect I won't see anything physically wrong and that's where I won't know what to do to try to get this thing running better in that throttle position. Boy is a new OS carburetor expensive. I don't think I'll be doing that. There's got to be a nugget of gold hiding in new OS parts somewhere.

rcbence

Yes that is what I ran the first run. This last weekend I tried a mas s2 11x6. Today on the ground I had an apc 11x7 on it.

I don't think the engine needing more running in would cause a specific throttle position to be leaner than everywhere else as my new post above?

Thanks for the help, I ran out of ideas to try before I fly this coming weekend again. I thought all was well until I dead sticked again this last weekend 😑 Its runnable but doesn't seem right. I think for some reason the low speed control valve is allowing a little bit less fuel in this one specific throttle position and I don't know why.

Actually I forgot there is one thing I could try which is putting back the baffle in the muffler. I don't believe I ever ran it with the baffle ever since it was new.

Would that really cause my specific problem? If that pressurizes the tank a little more than I would have to lean the needles out a little to compensate. I would feel I would end up with the same problem with the baffle in the muffler with one throttle position being leaner than the rest still.

the Wasp

My Feedback: (1)

Dude; you do NOT adjust the idle screw first! because the Idle screw bleads off the High needle, so you first adjust the High, then adjust the Idle.

I will ask a 3rd time. what glow plug are you using?????? tell us what brand and what heat range!

BTW Propworm shows us in the video on page 1 of an OS 46 running nicely with an 11x6, your engine is a 55, your engine has a longer stroke and a larger bore. keep the 11x7 on it,, please.

Jim

the Wasp

My Feedback: (1)

LOL I knew it was a 14" prop. it looked too long to be shorter than 14". a 61 turning a 14" prop. you had it running nicely. the way your plane lifted off I think it could have carried a bit more weight. but you won anyway.

Jim

Propworn

My Feedback: (3)

Yes It could carry a bit more but the other team could not so there was no reason to do so. I might add that a lower wing on the fuselage though a bit shorter was added with the thought of producing more lifting area. I know this exceeded the 1000 sq inches I just wanted to see if the same engine could lift more weight. I flew it empty but never altered the payload bay to carry more weight. It still hangs from the ceiling in the shop for another day.

rcbence

Why are you being willfully and ignorantly blind? It's been in the first post I made since the very beginning. I already told you a second time that it was in the first post and put it in a second post saying what plug I use. Why are you asking over and over when it's obvious that I have had the answer from the beginning? What's going on there?

And why do you so badly want someone to run a bigger prop? Are you worried I'll make more power with the smaller prop? Because by sight and feel it certainly does. I didn't notice any gaining speed or pull with an 11x6. I don't believe an 11x7 is going to pull harder or faster than a 10x8 either. I'm sure it'll work good though and maybe be better all around. The engine sounds good with a master air screw scimitar 11x7. With an 11x7 APC I can already tell it's revving up slower and working harder. I can't imagine what a 12x7-8 or 13x6-7apc would do. Like the manual recommends. That's not me saying that someone can't use it. This engine is rated at almost the same power at 16,000 RPM as the
.46. Have you looked? At that rated RPM it's barely making more than the .46. Although it probably does have more power throughout the power band and in the middle. I don't doubt that it can swing a slightly bigger prop. But what the OS manual says seems out of place to me. What engine is not rated for where it makes its max power? Clearly the RPM is where it makes its max power. The farther away you go from that RPM the more power you will lose. I'm pretty sure the engine's not making that much power at 9,500 RPMs. That's pretty far away from where it's rated for its max power. I have to believe most of the difference felt would have to be while throttling it and in the mid-range compared to a .46. And what on earth are the secret conditions for the power that's rated at 16,000 RPMs? What on earth was that? You're saying it's not some simple practical thing? That the power rating is only for the .1% that want to take it to the max with a tuned pipe and porting and what not? What?

So the power rating of a Kia Rio is only rated for the .1% that want to turbo it and blow it and take it to the absolute max? It's not the practical, simple and realistic power rating at what RPM it makes its most power? Where do you find that info? Is that in the OS manual?

What cons are there for an engine that is not overloaded and running cooler? I wouldn't care that it's spinning a little bit more RPM. The RC cars are spinning much more RPMs than these airplane engines. Aren't these ABC ABN engines designed to spin high RPMs? We're not even talking about going to its limit, but you sure make it sound like it's a horrible thing to run a 10 or 11 inch prop. A 10x8 won't take this engine to the limit.

I have to agree with others that it's mostly for noise and marketing tactic to suddenly jump up to such a huge prop selection for a .55.

Now just recently I tried putting the baffle in and tested it. My little issue is still exactly the same and it tunes exactly the same and the ratio between the needles is the same. I cannot have my low speed tuned any leaner than it is. My low speed needle was exactly the same with the baffle in and didn't need any change once the high-speed needle was adjusted. Which with the baffle it needed to go at least a half turn leaner to get the same fuel flow without the baffle. Once I did that my low speed needle was the same and fine.

But how the engine tunes did not change at all with or without baffle. If I tune my high speed to 3 to 400 RPMs rich, it's a bit too rich just under half throttle and will stutter and be a bit too rich coming out of it. If I lean my high speed just a little bit it clears up my mid-range just enough to be crisp. But now I don't have my 300 RPM rich setting at wide open.

I cannot tune it that rich to drop the RPMs that much without making the mid-range a bit too rich. I would go leaner on the low speed to clear up the half throttle but I can't go any further. Because my idle and part throttle will sag out and die from being too lean.

Why are you implying that I have no idea to tune the high-speed needle first? As if I don't know that and have not been doing that? At a part throttle setting it doesn't even make that much of a difference anyways. The low speed needle is the main restriction and makes way more of a difference at small throttle openings than the high-speed needle. Once the low speed needle starts coming out of the hole from the mixture control valve the high-speed needle starts making a bigger difference. You automatically imply that I haven't been doing that. It's been awhile since I've been into the airplanes but I've been doing the nitro car stuff pretty consistently for years.

My original post was in part my fault but not completely because I still have somewhat of an issue. The balance between the high and low speed needle seems to be a little bit off to get a perfect tune.

That is unless 300 RPMs rich of peak is too rich? But that's all I've ever read to do. Some say to go even richer than that. If I go even richer than that I'm starting to risk a dead stick for how rich it'll be in the mid-range. I can get it clean enough in the mid-range but I won't have 300 RPMs rich. It'll be pretty close to peak RPMs to clean up the mid-range enough.

I already said that I ran multiple glow plugs and tuned with them. You probably too afraid to go back and read the very first post I made that has what glow plug I use. Once caught in a delusion always in a delusion right? To acknowledge something would mean to have to face self. So someone thinks they're not in it by continuing it! That'll fix it!

Anyways, that's my problem here. I'm not able to richen it to the desired amount of at least 300 RPMs without being rich in the mid-range. I messed with the low speed needle while just under half throttle with engine running and it affects it quite a bit. The high-speed needle effects the half throttle position quite a bit also. If only I could go a little bit leaner on the low speed to lean out that mid-range so that I can run a little richer on the high speed needle. But I can't because it'll sag out and die at part throttle if I turn my low speed to where the mid-range is crisp.

The baffle didn't change this balance issue. I'll probably run it with the baffle and see how that goes anyways though since the power loss was about 2 to 300 RPMs with the 11x7 scimitar. I'm sure it's gaining a good amount of mid-range power and part throttle power throughout the power band with the baffle in. If it's anything like a two-stroke dirt bike pipe..... If you gain a little on the top end you are likely losing throughout the rest of the range below it.

But having the baffle in didn't change that I cannot richen the high-speed needle enough to get that 300 RPM drop without being rich in the mid-range. I would have to do a compromise and lean the high-speed needle a little bit to where it just clears out the mid-range pretty good. Now I'm not 300 RPMs rich at wide open anymore. That's what I'm dealing with.

The glow plug changes had no effect on what I'm talking about. That's not me saying glow plugs make zero difference for all things.

the Wasp

My Feedback: (1)

lets keep in mind that "I am trying to help you" understand these small glow engines better".

go back and read what Propworm said, your engine will run it's best between 10,000-11,000 RPM. with an 11x6 you are turning up your engines RPM higher!! go back and read the 50sx test in my link, the 50sx will twist an APC 11x8 at 11,000 AND an APC 12x6 a 10,950. so with an 11x6 you are turning a good 1,000 RPM higher. so, the smaller you prop is, the higher your Idle should be. because the smaller your prop is the less load the prop has on the engine.
so the longer prop has more momentum. that helps with your engine Idle.

even "Jaka54" (post #10, page 1) told you that an 11x6 is too small for your 55AX!
thank you Jaka54!

go back and read what I told you about prop and the flywheel effect.

I told you to use an APC 11x9 or 12x6. as the RPM numbers for the 50sx show these props are NOT huge!!

what that other guy told you> "shoot for 12,000-13,000 is totally wrong!! both I and Propworm told you to turn between 10,000 -11,000. so if that mean a larger/bigger prop, then use a bigger prop than an 11x6!

forgive me for not seeing you are using the OS 8. you could have simply answered the first time I asked, as I said "I am trying to help".
my new question is>>>> have you pulled your plug and looked at the element to see if it is bent???? I ask this question, because if your plug's element is bent you should throw it away.

bingo; that's the whole idea!!! with the smaller prop (11x6) your engine is accelerating too quick and turning too high of an RPM, and that makes it harder to tune!!!! as Propworm said!!

lets stop talking about 46, no reason to talk about it here..
because as my 50 engine link shows, the 50sx has about 1/3 more power more than a 46. so we understand your 55 has even more power than the 50sx.
sO, because we know if a 46 will twist an 12x6 happily, we know a 55 will happily turn the 12x6 even easier and higher than a 46 will!

a longer prop like a 12x6 has more "momentum", more momentum will help your idle better and midrange.

I already told you. let me say it another way. every engine has a "Power Band", it's peak torque point is where its peak efficacy is. run outside of that powerband you lose efficacy. if you run way outside that efficacy your engine will overheat and lower the life of your engine. sO again, an APC 11x9 or APC 12x6 is NOT too large for your 55ax.

Propworn

My Feedback: (3)

If you watched the video on the 46 the engine was new out of the box. I always do my initial tune and run in on a test stand. My stands allow the engines to be run in any position and the fuel tank to be set with the center of the tank on center of the needle valve. I always start with the engine in the upright position. The engine is always set up in its stock out of the box configuration.
I tune and prop the engine for 10,000 to 11,000 rpm with the best transition i can achieve. I do not use those exhaust deflectors as I find they affect the engine and can make tuning a bear. When I get the engine running to my satisfaction with a nice prolonged idle and good transition to high speed then i will reposition the engine on the test stand to match the instalation in the model including the height of the tank to needle valve. The engine should run the same. If not I attempt to find out why. Usually it is tank height that is the most common problem. Next would be the distance the tank is from the engine. An attempt to duplicate the position that was perfect on the test stand with the fuel tank. Sometimes you can only get it close then duplicate it on the stand and try and retune. Most times it works. Once satisfied install it on the model without the cowl.

Without changing anything tuning wise run the engine. If there is a problem its most likely the instalation. Its easy to kink the fuel line both inside and outside the tank. If you try this on the tank on the stand then on your plane this will tell you if there is a restriction. With fuel in the tank remove the fuel line and pressure line. Blow through the pressure line and observe the amount of fuel streaming out the fuel feed line. It should be the same for both. Work at getting it running satisfactorily with the cowl off. I have even done the first flights without the cowl as it makes working on the engine easier. When your happy then install the cowl. Run it do not touch the tuning. If it runs poorly the cowl configuration is the problem. Usually not enough cooling open up the exit holes. I start with at least 2 times the area of the inlet. If there is not enough exit area in your exit there may be higher pressure inside the cowl at different rpms giving you fits with the tuning. You may have to open up the exit holes even more than twice the intlet. I have even had to install baffles inside the cowl to direct airflow over the engine.

No one has mentioned that adjusting the needles should be in small increments but you need to allow the engine to run for a few seconds before testing as it takes a bit for the fuel air mixture to equalize to the changes you made.

In the case you present you have moved the needles all over the place. Remove the engine from the model, mount on the test stand as in this post, reset the needles as in my previous post, just get it running high speed adjusting the rpm into the 10,000 to 11,000 rpm range by sizing the prop. Forget the dang 16,000 rpm thats bullcrap. Use my two posts to set the motor up. Forget the deflector. The baffle is for sound control it effects performance very little.

I'm not sure but some of your posts seem almost to argue with advice you are asking. As if you are attempting to convice that you think you have determined fault is with the equipment. In my experience that is rarely the case. As you have found replacing parts can be very expensive. A lot of great advice has been given, work through it. Forget what you know from your car days, forget 16,000 rpm, relearn from the advice given.

Good luck

1QwkSport2.5r

I do not recall seeing mention of what muffler the OP is using. If there was mention, I missed it somehow.

Here are some facts. OS engines are known for being incredibly user friendly. They’re not super tight, so they are broken in much quicker; as such, they readily take a good needle setting rather quickly and are generally trouble free unless the liner peels. As mentioned, set the high speed first. Start rich and work leaner on the high speed at WOT. If you lean it and hear the rpm drop, richen back up until it starts to burble a little, and lean it *just* until the burble goes away. High speed should be a few hundred rpm richer than peak. Set your idle mixture at no less than 2,500rpm. Start rich (it’ll burble in the midrange) and work leaner so it will run stable at around 2,500rpm. If you try idling at 2,000rpm or below, you will not get a proper low speed needle setting due to the airspeed in the carb being too slow. You want your idle mixture set so it can idle reliably for a reasonable time (as if coming in for a landing for example). Maybe 15 seconds, and throttle up cleanly or with an ever so slight burble. Remember, lean engines quit. Rich engines burble and miss, and rarely quit.

*** If using a Pitts muffler *** You may need to plug one exhaust outlet to increase tank pressure. Pitts mufflers are notorious for causing engines to run lean. Plugging a tube will usually clear this problem up.

the Wasp

My Feedback: (1)

here is an older OS 50 FSR, turning an APC 12x6 at 10,860 peaked on 5%.

You Tube

OS 55AX, first run , on 5%,,, APC 12x6,,, 10.920.

You Tube

same engine^ same prop^,,,,,,,,,,,,,,,,,,,,,,, 11,190

You Tube

jaka54

That's the way to run in any glow ABC, ABN or AAC engine! You start them at idle and the give full throttle and adjust the high speed needle so that the engine run a little rich , then adjust so it runs nearly at full rpm , then a little rich and then nearly full rpm, the rich again and you do so for one tank. Then you can fly it!
Simple as that!
And 5% nitro is all that it takes to run any OS engine! Why bother with 10 or more??
It seems that some modelers think that the rpm manufacturers say where their engines give their max power is the goal to reach when they (modelers ) prop their engines. This is totally wrong.
You prop the engine to where it gives the best flight performance for that particular airplane! Simple as that!

rcbence

While I wasn't saying that out of an absolute goal to hit. It's just that I believe it does make its max power higher up in the RPM. And that loading it too much will make the engine work really hard and that could end up being wasted thrust. I'm not trying to hit 16,000 RPMs but I do have the engine in a Great plains escapade MX Midwing and it's a sport plane that likes to fly fairly fast. So a giant prop just doesn't fit for me with this setup. I'm really liking the 11/7 master air screw S2 combination. But I do know it screamed with the APC 10x8 if I wanted some more power and speed. There was no lacking in straight up vertical with that 10-in prop. But the 11/7 seems pretty good all around to me. Even with the baffle and it'll hit just about 13,000 RPM on the ground with the 11x7. The engine sounds healthy to my ears. It'll do a little better without the baffle but I've left it in for now.

the Wasp

My Feedback: (1)

let me say it in a 3rd way.

Powerband;
HP (Horsepower) and Torque is NOT RPM. RPM is controlled by what prop you twist. and Horsepower and Torque is controlled by the Nitro Percentage and Muffler type and Glow Plug type.

every engine has a Power Band where it runs and pulls it's best in. over revving an engine higher/over/outside it's powerband will put the engine out where it is most efficient.

what did I tell you? an engine's PEAK Torque point is where any engine is most efficient.
to add, an engine's peak Torque point is LOWER on the RPM scale than it's peak HP (Horsepower) point is.

go back to my OS 50sx link. the 50 turns and APC 12x6 (10. 950) only 50 RPM less than an APC 11x8 (11.000). yet it will only turn an APC 11x7 at 11.200.

Bingo; put an APC 11x9 or 11x8 or 12x6 on it. you will get your engine to run closer to it's peak Torque point!

Jim

rcbence

I really liked how it flew with the 10x8 the first time I got it in the air after a long time. Well for speed anyways and strong pull at wide open. I don't have an 11x8 but I wouldn't mind trying one. How does someone know where the actual peak torque is on any specific glow engine?

I know with two strokes in general that the torque curve looks more like the horsepower curve compared to four strokes as far as what RPM it makes peak torque. I know this is going to vary like all things do, but often the peak torque on a two-stroke is nearly the same RPM as its peak horsepower. And with the torque curve of course there would be an ideal range that you would want to be in when accelerating. Or it would be important if there were gears and we were shifting gears in drag racing. With an airplane you just go to wide open for max power so...... I believe if someone wanted to get the maximum power out of their engine that they would get it to the RPM that it produces most power. That's not saying that it's the ideal prop for anyone...... It's just that if let's say the peak horsepower is indeed around 16,000 RPM....... Then that's where you would want to be if wanting max power and pull from the engine.
You wouldn't want to only go up to 4,000 RPMs on a Yamaha banshee would you before shifting? You would shift right where it makes its peak power or near that.

I don't know what the torque curve or horsepower curve would look like on these engines exactly. But usually HP on a two-stroke is pretty steep and straight up and then it goes down fast after peak HP. So any lower RPM would be making less horsepower than peak obviously. And are you sure the peak torque isn't nearly at the same RPM on these glow engines as the horsepower?

How much power is the .55ax making at only 10,000 RPM max? Let's say that is the max because of a big prop...... Now you'll be accelerating constantly at much lower RPMs than that to get to 10,000 RPM.....where it might start pulling a little bit harder at 7 or 8000 and that's pretty far away from 16000. But of course the engine would tell you if it's really loaded by how it accelerates and how it sounds and how hot it's getting and what it tunes like.

I don't know but it must be quite a bit less power than at 16,000 RPM. I don't know of two strokes in general that have such a broad peak power that stays for thousands of RPMs above a certain horsepower level. I'd have to guess then that it's significantly less at 10,000 RPM. And that actually might be quite a bit lower than peak torque with the above that was said, that they often make peak torque near the same RPM as horsepower. And if that's true with these engines, then a higher RPM would be more efficient.

I'm not saying someone wouldn't like that or that you can't do that or that it won't work for a certain plane. Obviously there's multiple factors. But I don't see any hurt right now with hitting about 13,000 RPMs with an 11x7 mas s2 with baffle in place. So then it probably should be a little bit higher once it's in the air. I don't know how much.

As far as how it's running with an update since I flew it earlier today. It seems to be better. And I didn't change anything except go through more fuel since the first post. Originally if I tuned it only 2 to 300 RPMs rich of peak...... My half throttle would be so rich it would load up and die. Literally unflyable which caused my first dead stick because I thought all was well based on how it ran at wide open throttle tuned slightly rich. Well I didn't realize that it was a lot more than slightly rich at half throttle.

At that time the tuning window was huge. From peak power I could turn the needle almost one full turn before it would sag out from being too lean. Almost one turn of moving the needle and the RPM stayed exactly the same. I turned the needle in a whole bunch until my mid-range was only slightly rich and I flew it that way at that time. It was not set to where it was a little bit rich and dropping some RPMs at all. It just was peaked for almost a full turn.

​​​​​​Then recently all of a sudden the tuning window shrunk and became what I would expect. I cannot do that anymore and crank the needle in almost a full turn in. At some point it suddenly changed and I didn't do anything to make it change. I think my answer is that the engine is still running in. My only guess is that it didn't have very good fuel draw at wide open throttle and now its better? I don't know if thats the case but now the window between slightly rich and too lean is like a quarter turn.

Today was the first run that I mixed my own fuel for this engine. I was using up some powermaster 10/18 that I had sitting for a while that I added 2% castor to make it 10/20.

My own fuel I mixed was 11/20. 50% synthetic 50% castor.

I wasn't ready to pick up 5 gallons of methanol at the drag strip yet so I bought a four pack of the heet gas line antifreeze in the yellow bottles at walmart. It's just methanol. Even the MSDS states 100% methanol. Overpriced methanol of course through the deception of marketing making it sound like it's something else and some special thing.

I have a bunch of nitro left in a 5 gallon pail that's a few years old that I was wondering if it's still okay. Well the nitro seems to be okay because it ran great with my fuel mix. It's tuning more like I would expect it to. I can richen up the high-speed needle some at wot and not have the mid-range suffer and be so incredibly rich. I don't know........ I guess the engine is still running in some because its better now and the Escapade mx flew really nice.

I did do a test the other day on the ground for fun with straight methanol and oil. With the stock shim and os number 8 plug I would never fly it the way it ran. The tuning window was incredibly narrow and the needle was sensitive. It was hard to find a happy middle and the RPMs were down some. But more importantly how it runs in all other throttle positions wasn't as good on zero nitro.

So I got a feel for how it tuned and behaved with the stock engine setup, then I removed the shim and put a hot os plug in it at the same time. The tuning window mostly returned and was pretty decent and it picked up some power and it was only just slightly down from running nitro with the stock shim at WOT. Other throttle positions could be better so I don't know that I would actually fly it with no nitro still. I don't know what the compression is of the engine without the shim installed. I suspect it's not high enough to be ideal with no nitro. Still around .021 squish clearance without the shim on this engine. And I'm not sure what the volume of the head is. I don't know how to calculate the compression by adding or removing shims alone. How much is the compression increased from removing a .007 shim?

I don't know but it seems like this engine stock is set up to handle 25 or 30% nitro based on almost .030 clearance with the shim in place. But maybe not.

I may test how it runs on the ground for fun with 10% nitro and no head shim. If it can handle 30% nitro stock then maybe this is the ideal setup for 5 to 10% nitro without the shim?

My thunder tiger doesn't have any clearance without a shim. I measured it at slightly in the negative so it needs a shim. And even the thunder tiger manual says you can use 5 to 15% nitro for more power with it, and it seems to be a pretty high compression engine stock. I don't think this OS .55ax is as high compression so I'm thinking the OS might handle up to 30% nitro. Not that I'm going to run that much, I don't want to but it would be nice to know what the compression is without the shim.

But its running pretty good now so ill likely continue to use a little bit of nitro.

Propworn

My Feedback: (3)

There are some that go to the field and fly all day never touching their bone stock engines. If you bother to observe these are the same guys who never seem to have a dead stick. Then there are others who are always twisting needles, changimg props, glo plugs, you name it. They never seem to get it right and most flights end up with a dead stick or sagging engine. You seem to be more interested it trying to impress with all the hoops you think will accomplish a good running motor when all that was required in the first place was to pick the right prop for your engine.

Lots of good information has been given which apparently you choose to ignore. Insteas you continue trying to convince everyone you think you have all the answers that obviously are not working for you. The OS line is one of the most user friendly engines out there and any 12 year old can be shown how to get and keep it running properly.

This thread and your posts have turned into more entertainment than a help thread. Should be listed as a how not to do thread. Carry on for entertainment purposes only don't try this at home LOL

the Wasp

My Feedback: (1)

Propworm. a flying friend at the field had a MDS 61 with a gold head. I had seen him fly his plane/engine few times. a good flying friend he was. well this day he could not get the plane off the ground. it took a long take off to get light/make lift. and just before liftoff the engine would stall every time. 3 hours he and another friend work on it, tuning and tuning, changing plugs. every time the engine would stall just before liftoff. well after those 3 hours I waked over and asked if I could stick my nose in,,,, the answer was please do. I saw the problem instantly. it was a 61 engine with a super light Zinger 9x4 prop. I told him he needed a 12x6, he said that he did have a 12x6 on it and it ran great, so he went to his truck and found 12x6, and put it on his engine. his problem was gone instantly..

Jim

the Wasp

My Feedback: (1)

Propworm. I'm starting to get the feeling he is just "screwing" with us!


rcbence!! if you are not playing games here, you have GOT to get the number 16.000 out of your head!!!!!!!!!!

what did I tell you??? to turn 16.000 correctly you need to burn 30% nitro or higher. and use a Tuned Pipe.