I would like to get more power for my ST 90. There are few alternatives to going bigger than the .90 2 strokes as the next step up significantly adds weight. The only real alternative I have seen is the new O.S. 120 AX, however, I don't think it's worth the money to shell out for 20% more power. I don't do 4 strokes either.
Basic question: What are some basic ways to get more power from a 2 stroke engine? I know a 'tuned' pipe will give you more, but how hard are they to mess with? Any other suggestions would be appreciated.

larger carb with a pump,higher nitro fuel a pipe will add some power but it depends how the engine timing is setup as to how much.usually when using a pipe the exhaust poets are timed to open/close a bit soone and a bit later.material is removed from the top of the exhaust port.

i have 2 friend's at my field that run saito 125's in there's they fly awesome..

What kind of plane?

Actually, believe it or not, I've found that I get better performance with 5% nitro in my ST's. 5% and a #3 plug. And it's the same from my 45 up to my 90. For instance, on my ST 70 mounted on a Katana with a 13X4W prop, I got about 420 more RPM with the 5% than I did with 15%. Both had 18% castor. It pulls out of hovers better, the midrange in the throttle is smoother. As far as the tuned pipe, there are threads on here on building them. Or, you can be lazy and cheap like me and modify an oversized pitts ...

If you want to run a higher nitro fuel in the st you may need to add a shim under the head to lower the compression ratio.They used to be included with the older engines

There are guys in the tach reading forum that had things they did to ST90's . One of the best was a 1.08 Magnum carb for about $39.00,some claimed almost a 1000 rpm increase. My ST90 also ran better on 5 % turned a 14x6 APC 10400 with a pitts muffler. Nothing to brag about. It has since been replaced by a Saito 100 that turns a 15x6. The ST are higher compression and without shims you might not want to go above 15% nitro.

I have the ST .90 with a Saito 125. It's a good Power to weight compromise. It will pull straight-up out of a hover, but it's not a rocket.

The OS 120 is a bit heavier, I think. You might try experimenting with props before you buy a new engine. BUT...if you buy a new engine, don't compromise. Get the best engine you can afford.

I have 13 gallons through this plane...on my second engine now. You'll love it with more power.


OH YEAH....and don't confuse RPM with power.

Ya'll a giving advice and have no idea what kind of plane it is. Your wasting your time

Golden Skies Bampf 3D

doesn't matter what plane it is the question is about how to get more power out of the st 90 engine.the mods will work no matter what plane it's in.

http://www.goldenskiesrc.com/newbampfpage3.html
Here's the plane Happy Feet.

NOW let's hear YOUR sage advice.

that's a nice looking plane.

Jett 90 = more power problem solved.

kc

Nice looking plane. Sorry no sage advice but engines perform differently on different planes. You should know this. A simple 46 fx on a trainer pulls it around just fine for a huge no aerodynamic flying box but put the same engine on a Shrike with a simple prop change and you now have a sweet 100mph plane.

How can you give advice when you don't know what your talking about (meaning the application). I see this here all the time. Some guy innocently asks "hey will this work?" We don't even know what he's talking about but everyone is replying "oh yeh it'll work just fine but make sure you do this and make sure you do that" For all we know the guy is building a boat and your telling him to use a 16/8 prop.

I think this qualifies for Khodges "Dumbing Down" theory

Thanks, "Sage"

Part of his power problem is that Golden Skies recomends minimum engine displacement of 1.08 for this airplane and up to 1.60 based on their video. The booklet says 90 is ok for sport flying.

A Performance Specialties Ultra Thrust Muffler would probably help increase the 90 output.

the question was how to get more power out of a 90 sized glow engine (a Super Tigre) without going to a larger displacement and regardless of the application be it on a boat, plane, car, of bolted to the picnic table in his/her back yard the answer is still going to be the same.

kc

kc pretty well stated what my response would be. You could always say "changing the prop MIGHT give more usable power". But even then you would be dodging the original, and only, question asked.

One more thing. Can you please point out the post in this thread where someone/anyone said "oh yeh it'll work just fine but make sure you do this and make sure you do that"?

IMO you STILL haven't given any usable advice in this thread.

or any other one

not that i'd really notice it anyways

kc

For some reason idk why i thought ST stood for showtime here lol my bad i shouldnt have commented without knowing full details..so yea my commetn was also useless

Me too. ST 90 sounds like um. ST-90. Oh well.

Never mind.........................

There ya go!

Reading through this forum you have at least four ideas - 5% fuel, magnum 1.08 carb, large volume pitts muffler, ultra thrust muffler for more power from your ST90. These suggestions might give the increase your looking for.

I researched going with the larger carb a while back for this same engine. What I found is that the carb gives higher rpm on the ground but in flight doesnt give any drastic performance boost. I am not an engine guru and cant explain why this is so but that is what I came up with after hours of reading through post and PMing other RCers.

On my ST90 I put a jett muffler (similar to the ultrathrust) on it. I went with the 120 sized muffler because I was after more torque rather than top speed. It gave a power boost but not a huge one. The plane really sings on a 13X6APC now but is a little too fast, I was really looking for something to boost my performance on a 14X6. Those mufflers are pretty pricey too.

I am looking into the OS 120 now. Weight wise its almost equal to the ST90 and has gobs more power. If my 120 jett muffler will fit it I think I going to go for it.