NM2K

My Feedback: (14)

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I would run the engine on the 15% that you have and see if there is a problem. Probably won't be. If it does suffer from preignition, another head gasket will take care of it.

For just accomodating "knock", I don't get involved with miking shims, etc. It isn't that critical. You just don't want to damage the engine, not win a race. <G>


Ed Cregger

buzzingb

My Feedback: (2)

I still haven't burned any 5% or lower fuel in this engine because my fuel supplier is out and will be ordering more in a few months. I routinely run this motor for 20 minutes on one tank (12oz)fuel. It will run for 25 minutes if you are just sport flying with not too many wide open burst and vertical climbs. I love the vertical this engine provides, its alomost as fast as horrizontal flight.

buzzingb

My Feedback: (2)

I want to leave this little engine at home and get some more time in on the 90 but I must say I will have to wait a while till the new wears off so to speak. The power has me under its spell and I am just enjoying playing with this engine too much.

Squinty1

My Feedback: (3)

Now I have a story to tell about the G51 vs OS46ax I`ve read lots of articles on RCU about how much more POWERFUL a G-51 was over a OS46ax. Well, Me and 2 other of my 3d buddies has 3 of these engines and I bought a OS 46ax also. We put these engines on Katana GS40 profiles. After all the engines were run 1/2 gallons of 15% nitro we all put towerhobbies mufflers on all the engines since they give the best rpm increase of any of the stock mufflers. SO they same airplanes the same mufflers the same fuel the same prop apc 11.5x4. We could not get any of the GS51`s to pull out of a hover Although with the OS46AX we had PLENTY of pull out power. NOW THEN, TACH numbers - same fuel same props same mufflers GS51 tachs 12.5k-12.7k maximum OS46ax tachs 13.2-13.6k After many many days of tuning on the 3- GS51`s none of them would tach over 12.7k now we have over 2gallons of fuel through each of the G51`s with no IMPROVEMENTS. Now with the stock muffler on the OS46ax and the G-51`s with the stock the G-51`s is more powerful by a little but when you put the tower hobbies muffler on all of them they really wake up "expecially" the OS. So I can`t understand how people is getting more power out of the G-51.

buzzingb

My Feedback: (2)

Well all I can say is bolt a 12X6 on the OS 46 and see how it pulls it. I won't say that the OS won't out spin the 51 with smaller props because I haven't tried it but with a 12X6 I know what is going on . I had two OS 61FXs that couldn't out pull this 51 in the air with a 12X6. On the ground rpms is very similar with the 61 but in the air the 51 has a slight edge over the 61. The first engine I had was a 46FX and about all I ran on it was a 11X6, 12X4 or 12.25X3.75. I must admit I never mounted a 12X6 on it but I knew it couldn't pull it as I did mount a 11X7 on it once and it like to bogged it down so bad it wouldn't even fly. Don't get me wrong here I have flown OS before (46FX, 61FX, 61FX, 50SX) and I may fly OS again but they are just too pricey for me and the liner and bearing just don't hold up to my expectations. Someone told me to use a small prop on the ST51 but after I have the 12X6 mounted I don't know if I will ever be able to take it off it pulls it so well.

Hobbsy

My Feedback: (102)

Squint, you have to remember that some engines are not happy turning high rpm and the ST .51 is one of them and yet it will turn a Graupner 12x6 at 10,500 rpm all day without a whimper. I suspect your OS .46s will over heat if you try that.

buzzingb

My Feedback: (2)

I get 11,200 on the ground with a 12X6 Master Airscrew K Series but where this engines comes alive is in the air. It will spin this prop as fast or faster that a OS 46 will spin a 12X4 and what I am basing this on is as the prop starts to reach .7 Mach or there abouts depending on air temp and density the tips start to resonaste that sweet sound of super sonic waves (buzzing the Prop). I could just barely get my OS 46FX this fast with a 12X4 useing high nitro fuel. Now OS46FX is in the drawer with a peeled liner and second set of bad bearings.

Hobbsy

My Feedback: (102)

Buzz, I just got a pleasant surprise, I pulled the Davis Diesel head off of my .51, the last time I tached it as a glow was in the early 90s when it was new, it tached 10,500. After all these years as a Diesel it has improved significantly.

SuperTigre .51
Prop Graupner 12x6
Plug=GloDevil 2c
Fuel Fox 5%/20% castor

buzzingb

My Feedback: (2)

That is good to hear as I like to run much fuel thought an engine before I retire it. I have run about 3 gallong thought this one now and only have had it a few months. I may get 30 gallons though this engine this year.

buzzingb

My Feedback: (2)

Most of the people that fly don't burn but 3 or 4 gallons a year. I know the OS line of engies can't burn fuel at this rate and keep flying for long. They just aren't built to take it.

buzzingb

My Feedback: (2)

Does the Super Tiger 51 have a head shim? Has anyone removed this shim with say 5% nitro?

buzzingb

My Feedback: (2)

I was just researching timing in methanol motors and it seems that timing is very critical escecially if the mixture is a little on the lean side.

Harry Lagman

Squinty, that's the same sort of experience we've had at our field. The AX .46 is the stronger engine of the two both in terms of static rpm and in-flight performance in identical airframes.

Buzz, I have seen two separate guys running GMS .47s with MA 12x6s as part of an experiment and they both pulled 11,000 rpm ready to fly, so your engine is performing on a par with the .46 bunch.

buzzingb

My Feedback: (2)

Harry, are you saying the OS46AX will pull a 12X6 better than the Super Tiger 51 in the air? There is a difference in air and on the ground performance and there is a difference in the size of the prop also. So lets clarify what you are saying.

1. Have you flown an OS46AX with a 12X6? Have you flown a Super Tiger 51 with a 12X6? If so were the engines on the same plane, etc?
2. Second engine mentioned GMS47s did you ever fly the engines in the air withe the 12X6?

My ST51 spinning a 12X5 11,200rpms on the ground maynot be that spectacular but where I am really impressed with this engine is in the air. If the engines will spin a 12X6 in the air to the point that the prop tips start to resonate supersonic waves then maybe they are the same if not then there is a difference. Most of my comparisons are based on the previous two OS61FX engines I had. They could come close but not to the point of buzzing the props. Once again I am not speaking of any other size prop other than a 12X6 as I am aware the OS and GMS motors are/may be, capable of higher rpms with smaller props.

Harry Lagman

Buzz,

I have flown two identical models - one with a GMS .47 and MA 12x6 and another with an ST .51 and MA 12x6. I maidened these aircraft for their respective owners. Their performance was similar in the air. If I had to choose a performance "winner" from these two aircraft, I'd choose the ST .51 powered one by the slightest of margins. I didn't tach the ST but the GMS did an even 11k with the MA 12x6.

I have also flown several of these models since, including one with an AX .46 and APC 11x6, another with a TT .46 Pro and APC 11x6 and another with a GMS .47 and MA 11x6. These three models outperformed the two 12x6 equipped models by quite a margin, mainly of course due to the more appropriate prop selection.

I have not tached an AX .46 with the MA 12x6 but the AX seems to slightly outperform the GMS .47 on an APC 11x6 (12,300 rpm versus 12K even) so it's fair to assume that the AX should do at least 11k with the 12x6 if the GMS can. Using the APC 11x6 as a reference, the GMS .47 (12,000) and AX .46 (12,300) both outperform the ST .51 (11,800).

All the .46s seemed well over-propped with the 12x6. I would not recommend such a large prop unless one was trying to greatly reduce noise. The ST .51 seemed a little happier with the 12x6 than the .46 engines though. It seemed to be an OK choice for the ST and therefore if someone asked about a prop for the ST .51, a 12x6 would be among my suggestions in the appropriate airframe application.

buzzingb

My Feedback: (2)

I have the Thunder Tiger 46 now and it presently is on a Patriot but I have flown it on several airplanes with different props and I would dare say it won't run properly with a 12X6. I tried it once with a 11X7 and it didn't like it at all, same is true for OS46FX. I did run both these engines with and without Tower Muffler and neither got up to the rpms with a 12X4 that the Super Tiger can reach the a larger prop (12X6) and to top that off both were flown on the same pane a Ultra Stick 40. I even crashed the Ultra Stick with the OS46 onboare (stripped servo). However, I am not refuting your figures here because I haven't done the test as you say you have but with the engines I have flown (OS46FX, OS61FX, OS50SX) the Super Tiger seemed to have an edge over the other with large props. I will say this, even more than the power I like the price $69 if you consider the $10 rebate and the fact that the 51 won't peel the liner like the OS46 did.

buzzingb

My Feedback: (2)

One thing to consider here if we look at the 51 is that muffler is very restrictive. I wonder if a Tower Muffler would help the 51 like it does OS,Thunder Tiger 46s? I know the bolt patterns aren't the same but could the hole be elongated and use the nut on the backside.

buzzingb

My Feedback: (2)

I can't see myself mounting a Tower muffler at present power levels but who knows down the road it may be a possibility.

XJet

A mousse-can muffler makes a *big* difference to the ST90 so i expect it would do similar great things to the ST51.

As for prop sizes, most 45-47 sized engines are tuned to produce maximum power at around 14K-15K and that means a 12x6 prop is *way* too big if that's your goal. Indeed, SuperTigre claim the 51 produces its peak power at 15,500 RPMs so proping it for 11K is putting it way off that figure. Yes, you gain some benefit from the better efficiency a slower-turning bigger prop produces but it's still not going to see the engine producing its maximum power (unless ST are lying of course

I run most of my TT46Pros on 12x4 APC narrow-bladed props (pulling just over 13K RPMs with 5% nitro with Tower Muffler and Dr Cooper's magic elixor) because they're brilliant for 3D stuff but others in the club get their best results with a 10x7 on faster planes.

And let's not forget that not all props are created equal. It's really easy to get the tips ripping on an MAS prop (particularly the K-series) and a lot harder to do the same on an APC of the same diameter/pitch.

HighPlains

My Feedback: (1)

Did they change the ST carb sometime in the last 30 years? The midrange has always had an adjustment, you loosen the two screws that hold the main needle valve assembly and rotate the entire assembly slightly. Clockwise rotation richens the mid-range, so counter-clockwise will lean it.

XJet

That's the *theory* but I spent an entire day experimenting with the spraybar orientation and re-adjusting the needles to no real effect. My G90 still ran *real* fat in the midrange.

speedster 1919

My Feedback: (3)

Xjet-- Somewhere on the Super Tigre web site says all fat midrange problems are LS needle rich settings. A turn of about 1/16 lean on LS is the fix with a 1/16 rich on the HS needle.

Hobbsy

My Feedback: (102)

Buzz, the .51 has a single copper gasket, it should not be removed as it's there to seal not to shim.

NM2K

My Feedback: (14)

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Yes, they did change the carbs quite significantly some time back, though I'm not sure when this happened. They are grossly oversized for one thing and I am sure that is the main cause of the problem.

Remember the ST carbs of the Seventies and early Eighties? They were perfection personnified. I wish they would return to the older sizes and reduce the CFM capability to enhance fuel draw. I won't miss the two to three hundred rpm the engine develops when peaked flat out, but which you cannot use to fly with anyway because the engine will go too lean while burning off fuel. What the engine manufacturers are doing now is nothing but pure idiocy.


Ed Cregger

HighPlains

My Feedback: (1)

I'll agree to that! The engines were fantastic examples of engineering when World Engines had the line. It seemed like they went down hill rather quickly after they became part of Wallyworld. I haven't bought too many of the funky cast head/cast drive washer series. Thanks to the online auction, I find prime examples of engines like these.