I have a Phoenix 46 Sukhoi (55" wingspan ~ about 6-7 lbs). I currently have an OS-46FX on it, but am unhappy with the power. The thing is a slug. Great engine, just want more verticle, more power...and have been thinking about buying the ST-75 to get it. It's about 10oz heavier than the OS. the OS has 1.62 at 16000 and the ST-75 has 2.18 at 15600 and the ST-61 ABC has 1.85 at 16500 rpm and weights about the same as the 75. Curious of your responses to this engine/plane match up. Is the ST-75 just too much? Will the ST-61 give me what I want? Opinions please.

No one uses a 2-stroke at those RPM's. Take a look at the 4-strokes in either a 70 or 80. Dennis

.61 size engines are always a good option for .46 sized planes when more
power is desired. The .75 sized engines are usually about the same weight,
size, and price....so why not go with the .75 ?

Take a look at the Tower .75 engine as well, I believe it is a lot lighter.

FBD.

There is a K&B .61 that weighs almost the same as a .46
http://www.mecoa.com/kb/aero/aircraft.htm
Might be worth considering...

I would buy the .75 and judging by weight and wingspan that sounds just adequate. I have a Twist which is designed for .46 two stroke. I ended up putting a Evo 100 size 2 stroke in it and I'll admit it is way overpowered but the same plane with os 50sx was underpowered in my opinion. .75 sounds like a great size

I had a Black Horse SU31 which is the same as the Phoenix one ... I tried a TT46 and TT61, the TT61 gave me more power and more vertical but wing loading was high, engine weight and tail weight. It added about 12 oz more. So think carefully.

Thanks for your posts. I'll have to check on the wing loading of this plane and the weight of the Tower Hobbies engine. But the ST-75 is still at the top for me.

I used the k&b .61 and it worked grest and didn't add any weight!

finally! somebody running a kb .61. is it a twister? i started a thread a while back and knowbody got where i was trying to go with it- .40 size with .61 power. how about some rpm numbers?

Yes it was a twister and it ran good and throttled well. I have no rpm numbers but it turned a 11x7.5 with authority. Had more rpm than my ringed k&b .61 with the same prop and that one turned the 11x7.5 at around 11500 rpm.

unlimited vertical? the point i was trying to make in the other thread was that the kandb should make more torque in the midrange for better 3d. what's your take on this? plus it's still made in the usa i believe.

I didn't get to fly it alot as the aileron seperated from the wing on the 3rd flight(resulting in an uncontrollable spin) on the suchoi but it had unlimited vertical. It flew the suc well at lower throttle settings. I didn't get to try 3d with it but i think it probably would have pulled out of a hover. It had very good transition and idle. Lots of torque.

I've been running the K&B's continuously for over 30 years. They are wonderful
engines...but I have never yet run one with a K&B carb....always an OS, or now
days with the Magnum carbs. The biggest rub on K&B since the beginning was
the carbs sucked.....the perry's were even worse, but that's just my opinion.

The K&B .61 is the best replacement engine for the weaker .46's, because they
weigh the same, and put out way more power. I always run them on 15% nitro,
an oil blend with 1/3 castor, a K&B 1L plug, and a Master Airscrew 11-7 1/2 prop.

I still have my original 6550 I got in a trade, about '73....it was new, but was
missing the carb....five rebuilds and three crankcases later. I put an OS 7B carb
on it, and never looked back. Most Guys when you mention K&B will turn up their
nose....but I love 'em.

FBD.

I have had some problems with the k&b twin needle carb but the perrys and the new perry type k&b carb work great for me. I replaced the carb on my magnum .61 with a perry cause the magnum carb sucked(just a bad one maybe?). I also think the K&B twister had a little more power than the magnum.

Never thought of the [link=http://www.mecoa.com/kb/aero/aircraft.htm]K&B[/link]. but i'm going to now! Click the [link=http://www.mecoa.com/kb/aero/aircraft.htm]K&B[/link] link for info. on them.I, as long as most are happy with there K&B, might just go with this engine. The 6150 is lighter than the OS-46FX by about 2oz. and has .28 more bhp. The 6150 is about 13oz lighter than the ST-75 and only has .13 less bhp. My goal is to get my 46 Sukhoi to have ULV (unlimited verticle) and great mid-range power. As it is right now with the OS engine i feel like the thing is going to fall out of the sky or slip sideways on takeoffs.

On the weights I listed, they are all including the muffler except that I am unsure about the K&B. The page I linked says "engine weight" so i'm going to assume that is excluding the muffler.

The 6170 is the sport twister and is on special for 100$!

As much as I love the K&B's....the Tower .75 at $95.00 will whoop the
pants off the K&B's. They have massive schnuerle ports, a great twin
needle carb, and comes with a tuned muffler.

If you want vertical....put the Tower .75 in the .46 sized Sukuoi and see
what vertical is all about....it won't even slow down ! [X(]

Dave.

the tower is alot heavier though, right?

The tower .75 is 23 oz with muffler and the K&B is around 17oz with muffler(depending on which muffler). The Tower is very similar to a GMS. The difference in weight of the airplane is more than the amount of difference in engine weight. In this case the difference in airplane weight between these two engines would be around 12oz(more or less depending on where you could stick the weight) for the same cg placement. This can change the flight characteristics. My Phoenix Suchoi was extremely sensitive to cg changes going from fun to fly to spontaneous snap rolls during the fuel burn. The tank size allowed in the suc is also not very large. One would tend to think that the .75 might use more fuel than the .61. [&:]

Tower and GMS build a .75 or .76 in their .61 case, but if you really want power, OS & Magnum build .91s in the same .61 case. All of the .61-.91 engines, except the K&B, weight about the same.

You're not going to tell me the Tower .75 can run with a .91, are you.

As I said in my column a few months back, why would anyone buy a .61 when there are .75s and .91s available in the same crankcase-same weight, loads more power.

I weighed one this morning, still in the bags. Engine alone was .8 pounds. Engine and muffler was 1.1 pounds.

Thanks for your posts everyone. I think I'll go with the Tower 75 engine for 95 bucks. Some of you seem to be pretty happy with yours, so i'll give it a try. Plus it is only about 6oz heavier than my OS-46FX and has about .6 more bhp.

Buy the Tower engine on their "Savers Club" thing an it will double the
warrantee....to four years. Take the muffler apart and Lock-Tite it before
you run it....don't turn the engine over by hand before the first start-up.

Oil the piston and cylinder wall before you install the muffler, and pre-heat
the engine before the first start-up.

FBD.

The K&B barely fits in the cowl. Don't know if the tower will.[&:]