Yeah.

Those ST.45 ABCs are screamers. Mine was turning around 14,000 with 10~6 IIRC. Gonna put it back on the Lucky Stik when I get it repaired. Haven't run my NIB ST.51 yet but hope to get a couple S90K/G90s back in the air on some semi-scale acro types before too long. Gonna pipe them for 14" props to take advantage of this engine's torque. Using stock or Pitts muffs will only 'clean up' the installation and rob available power from almost any engine.

Terry in LP

JIM...are letting your Grandson 3D that Satio???? Capt,n

It seems very diffcult to make a conclusion when everybody has different ways of measuring the
performance. What it seems more reliable approach is to measure the thurst resulting from the
work of the engine+propeller and leave out the sentiments. Then one can see what the RPM versus
torque are producing also at given fuel, glow-plug, muffler, carb, temperature, humidityetc, all
which have HUGE effect on those simple glow engines. And after all it is very simple, only we
have to agree on the conversion between pounds and kilograms, which is no problem to take
it 2:1 about. Itried measuring the thurst and then I found that Pe Rievers has a pretty exact
Calculator which does the job, if I supply the RPM and propeller data only; try that at:
http://mvvs.nl/
and then go to the left on 'utilities' and download the propeller calculator.

After all most wecare about is thepulling force applied to the airplane at certain speed,
isn't it ?

Cheers,
Nick

Hey guys, I just got home from the field and once again I have failed to get the g-90 right. After sitting in my room for 2 years while at basic training and Tech school. I finally have the plane back. 3 dead sticks later, the plane is still in one piece, thank god. Here is the problem. It idles great, transitions great, and will fly around at anything above 1/2 throttle all day, But when you cut the throttle and try to slow down, it instantly dies. it is on a p-40 and only has maybe 1 gallon through it. I'm ready to throw this thing in the trash, I need help. The fuel tank is on center of the carb, It's not sucking air, But as soon as you lower the throttle, nothing. O.s. type F, 5% cool power, 12x8 graupner 3 blade. Tuned, re-tuned, and tuned again. I'm at a loss, Ready to melt this thing down Here are some pictures how it is mounted, Yeah I know it's dirty, Pulled it out of a wheat field today[&o]

I wander if you have tried 2 blade APC propellers 15x4 or 14x6 and got the same problem ?
(the 3 blade 12x8 looks great but maybe not the right one for G90). Also, it might be good to
get pump for the fuel anyway, or you have it in place already ?

I see you mounted the engine on its side, like I did on my spitfire MK2 using the same engine and bison L-shaped muffler. What I can tell right off from your photos, is that you also 180'd your carb placing the fuel nipple towards the prop, which ends up in a sharp turn to go back to your fueling port? Your hose could be restricting fuel at that sharp bend especially after the heat builds up under the hood and everything starts going limp from the excess heat.

I don't worry too much about getting the absolute most HP or speed from a model airplane engine. More often I am trying to achieve a combination of power/thrust/airspeed for solid control response and good vertical performance on the particular model. This leads to using slower turning, larger diameter props. I have tried some 4 strokes and prefer 2 strokes with tuned exhaust systems allowing the adjustments that are sometimes needed to get this type of performance. I have recently acquired a few liners for ST 90s and plan to do some experimenting with the porting, piping and propping of my engines.

Terry in LP

I have the line arranged so it makes a nice sweep around the engine back to the fuel valve. And how the plane will fly around all day at half to full throttle makes me think it is something else. Not tuning the low speed right? So far I have cut a little more out of the cowl to allow more cooling, replaced all the fuel lines and disassembled the carb and soaked it in alcohol and cleaned it thoroughly, and I have blocked one of the exhaust pipe on the pitts to get some more pressure.

I cannot see the fuel tank location from the pix's, I believe you are flooding out on idle ,because your carb fuel inlet is now lower then your tank. Instead of drawing fuel you are now siphoning. At higher speeds, no problem. My problem is tuning for level fight and in a nose up aditude goes lean.
, tune for nose up aditude and level fight is rich. Reason: In a straight line from clunk to carb is 10 inches add the extra fuel line to attach the fueliging point 2-1/2 more inches for a total of 12-1/2 inches of fuel travel. Even for a G90 thats alot of pulling and thats why I ordered a perry pump. Most manufacturers only recommend no more then 7 inches total to carb.

Mike

Alright guys, I need some help. A little info on my setup- I purchased the G90 second hand on ebay (perhaps the first mistake, I was waiting on getting the funds for an Evo 1.00 but oh well) so I have no history of the engines use or care of the engine. I am using a new SuperTigre Sport Glow Plug Medium Heat Range from towerhobbies.com. The prop on the engine as seen in the below video is a Master Airscrew 14x8. I have also tried and MAS 13x8 and APC 12x6 and all end in the same result. I think that I am not getting a rich mixture at all and the engine overheats and shuts off when I move past 1/2 throttle. It will idle for 5 to 8 minutes and shut off. I am not sure what I need to do. I am hoping that the video will shed some insight from you experts. Also, I am using Cool Power Max 15% as fuel.

[youtube]http://www.youtube.com/watch?v=kBHVuquATDM[/youtube]

Open up the low speed needle valve to where it extends half way across the cutout in the spray bar inside the carb when the throttle is wide open

Then start your set up

So that I am crystal clear that we are talking about the same thing, you mean the screw located in the center of the carb in this picture:

It seems that it all the way in, so I will turn it out and see.

That is correct

5% on the fuel wouldn't hurt either. The st's don't like or need nitro .

The low speed needle will affect running at high speed . Mine had to be set 1/3 the way into the cat eye of spray bar and using the pinch method at idle around 2500 to 3000 rpm adjust so there is no rpm increase when pinching and then adjust high speed again and recheck idle. After adding the perry pump all my problems went away. And said, I use no nitro, this engine does not like it. Running a master airscrew 13x6 K series turning 11,900.

I was wandering if anyone can help me make a choice. I have a 7.5lb Phoenix Extra 330s. I have been running a 15x4 zinger, but am looking for something better in 3d type performance (hovering/slower flying/harrier)

I have been looking at APC 15x4 wide [link]http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXFGW1&P=SM[/link]

and APC 16x4 wide [link]http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXFGW4&P=SM[/link]

or are there any better brands of probs for 3d type flying?

Also what should be the engines max or so temp?

St 90,
80/20 (Medical castor)
14*6 Prop.
Perry Pump.
10,200 Rpm
$8.80/Gal.
Not too bad!!!!!!

Hi!
First of all ...Change the fuel to 5% nitro!
If the Super Tigre is made in Italy (New ones are made in China) you better use 5% nitro as the compression is too high to use 15% nitro.

second: Use a Enya 3 (or 4) or OS 8 glow plug.

Third: Use a 14x6 APC, Graupner Cam-prop (Not the old gray one)or RAM prop! Those are the best plastic props today.
14x8 MA is no good.

Forth: Check fuel tank for leaks and use no more than a 14oz tank. See too that you use two clunks (Uni-flow set-up) for a more even fuel delivery to the carb.

And...Do run that engine first with a regular factory silencer so that you know that it isn't the silencer that is the culprit.

LION
Sounds lean. If you are not getting any change in the engine with the high speed needle you may have a blockage in the fuel system or have the low speed needle in so far the fuel opening in the spray bar is blocked by it.
Oh geez, that was last year.

I have a question for you guys. I have a old kit built Patriot that I am just getting finished up. I am deciding which motor to put in it and have decided to go with a 90 size. The choices available to me are a Supertigre 90 or a ASP 91. I favor the Supertigre but was wondering about prop sizes if I am looking for mild aerobatics but mainly speed. The plane has retracts and will have the fuse glassed so it may be a little on the heavy side but not by much.Any advice on props and also on which pipe or muffler to use as there isn't one on the engine now. I will be pulling it out of retirement but when my dad put it away a while back it was barely broke in good so after a good cleaning I am sure it will be fine.

I have a ST-90 that is not fully broken in yet and made in China. I have it installed into an old Super Kaos 60. I am using a APC 13/6 Prop 2-blade. The engine runs very good, and has unlimited vertical from the time the wheels lift off you can yank it vertical and climb out of sight. The muffler is stock, but I will tell everyone, the original mufflers for the China made ST-61, ST-75, and ST-90 run well but they are junk. After a few flights the internal baffle plate will dislodge and start pinging around inside the muffler and you will definitely hear it from the ground. If you want superior performance and are willing to forget about price, buy a tuned muffler from Jett Engineering. If you have the cash, buy his replacement carburator also and then you will have a real screamer of an engine. Here is why most people say ST Carbs are junk. They do not know about putting a squeeze clamp with rubber jaws like you will find in any hardware store to hold wood on top of the carburator and on the bottom of the engine and squeezing it slightly before you tighten the carburator clamp screw down. If you do this, you will avoid all the varying carburator adjusting and lean burn scenario. This will ensure you will not develope an air leak! Do not use a metal clamp to do this. The low speed adjustment is the hardest to set and get right, but a little minor tweaking of not more than a 1/8 of a turn at a time will get you a good idle and will affect the high speed adjustment also. Lift the model vertical and see if it dies out or slows down, if it does, you have the high speed too lean. If it will not idle and take the throttle opening smoothly, then the low speed adjustment is not right. There is nothing worse than the engine quitting when you advance the throttle for a go-around. Spend a little time on the ground getting the low speed right, and you will save yourself a lot of grief. You will not generally have to touch the low-speed until you get a gallon of fuel through your ST engine. After that you can lean it down or richen it up, whichever will result in a smooth throttle transition and a good idle. What you want to avoid is over propping the engine and getting it excessively hot. I use my fingers to tell me this. I go once around the pattern, quickly land and feel the head. If I can not stick my fingers on the head for a couple of seconds then it is too hot and too much prop, generally too much pitch. The engine should not slow down and labor as your pulling a loop. It should remain fairly consistent throughout the loop. Too much pitch and the engine labors and will get hot very quickly. I have seen more people smoke their engines trying to use too much of a pitch prop and then they wonder why they never run right after that. I am fussy on the fuel I use. I use OMEGA 10% Fuel that has some castor and the rest synthetic and my engines last a long time. The Castor Oil will save you in the event you experience a short lean burn say from a pin hole in a fuel line as long as you land and check it out before trying to continue to fly the plane. If you want a screaming engine, then use a good tuned muffler that is made for RPM increase. I have seen the difference between a MAC tuned pipe and a tuned muffler from Jett Engineering. A Jett Muffler will make your engine really scream in comparison. They may cost you up to $85, but worth every dollar. Well worth it when you keep a US Manufacturer in business that stands behind his product. Super Tigre Engines do not like a lot of back pressure. Back pressure holds in heat. I have pulled out with a lot of patience the baffle plate that came loose in side one of my defective ST Mufflers. Such a tiny hole in the center of it. The engine ran far better without the baffle than the muffler with the baffle. We just do not like the increase in noise level, so a good Tuned Muffler is in order. Now I have tried the MAC Tuned Black Muffler, but that is not where the performance is either. There is too much back pressure even with those mufflers, as MAC recommends reaming out the two holes inside of the muffler for ST Engine use. If they would buy ST Engines and test them before releasing their product to us, we would see far greater gains than the stock Tuned MAC Muffler perhaps. But with JETT Engineering, they buy engines and test them before releasing their final product to the public and we do not have to play Mr. Test Engineer after we buy it. It is ready to use out of the box. I have been running ST Engines for years and I enjoy their performance once broken in and properly tuned.

Many people have their low speed adjustment that is located in the center of the carb on their ST Engines way too lean, and it will quit fast and furious when advancing the throttle quickly to wide open if it is too lean.  Want to burn up an engine fast, just keep running the low speed adjustment too lean.  I adjust mine with the engine running and with a steady hand and fingers, and I have all of them intact and uncut, but I can not recommend this to everyone, but it has worked very well in my success of setting the low speed carburator adjustment correctly and my ST Engines advance smoothly even with a quick wide open throttle from idle.  Of course you can do it by trial and error and shutting the engine down for a safer method, but it takes longer.  Just do not turn the low speed adjustment more than a 1/8 of a turn at a time.  My ST Engines do not quit and will idle very reliably and not quit when advancing the throttle either.  Remember, small changes in the low speed adjustment goes a long way.  More sensitive than the high speed seems to be, I feel.  Personally, I think more people should use a Perry Pump that will maintain constant pressure to the carb no matter what attitude your plane is in and it will do this no matter how low or high the tank is in relation to the engine.  Not all planes allow for the ideal location of the fuel tank and a Perry Pump is the ideal solution for engines running lean after they burn off some of the fuel in the fuel tank.

I bought a 93" unflown Fiesler Storch model (built from robert schweizer plan) and it had a used ST90 in it. Previous owner/builder (who is a nice gent in his eighties and selling up) said he couldnt get it to run properly (it's mounted inverted).

Having some ASP90 two strokes handy, I thought I'd just whip out the ST90 and replace it with an ASP90 - easy peazy lemon squeasy.

But at our club swap meet I came upon a lovely brass (not heavy though) 'in cowl' silencer, not just for an inverted ST90, but specifically for a Storch (with 2 scale exhaust pipes as per full size) and price just £10 (about usd15)

So it seemed worth a try to get the ST90 running and if it seemed reliable actually use it.

To cut a long story short (after some experimentation) it was the ST carb !

Which (to be fair) is old, has been stood inverted in the model for around 10 years, and someone has tried to drill a hole into part of the main needle threaded part (presumably to extend it) but it leaks fuel a tadge in that area.

From what I've read here I thought I may as well try an asp90 carb (have an asp90 engine in bits for spares including a carb) stuck it in and the ST90 fired up straight away. Bit of tuning on the main and idle needle and hey presto.

14x6 apc prop is turning 10500 revs on 5% nitro fuel with asp 90 (2 stroke) carb and incowl silencer (for inverted) . Engine was running right way up on test bed. i.e. not inverted.

Very powerful engine! And it can go back in the storch with the bargain in cowl silencer for maiden flight.

Thanks for everyone posting info here - saved me time & money and a good engine.