I have been flying a Sig Something extra for quite a while and would like to get better vertical performance and like to be able to Hover with it. I currently am running a O.S. .46LA engine and am considering either a .46FX a .61FX or a .91FX. I don't care about the price of these three I just want the biggest engine and have it still fly great. Is a .91 to big or can it work.

Go with the .46 FX. Use a APC 12.25 X 3.75 prop. It'll hover and it will go unlimited vertical.

The Irvine .53 would be the largest engine you want to put on the plane.

If you add the weight of the .61 or .91, you'll ruin the 3D capability of the Somethin Extra.

You might get the performance boost you want just by switching props....

I would say go 4-stroke. i now it's not on your list but a Saito .72 on that bird is perfect. if your stuck on a 2-stroke. think about a high performance 2-stroke . My 1st choice would be a Webra .50. Other good choices might be MVVS or Rossi or Dub Jett. A.60 2-stroke would give it plenty of power, but at a wieght penalty. The .90is to big.later daveo

Still Looking for more suggestions has anyone ever really put on to big of an engine? I would like for it to accerate through the vertical. Is a .61 fx going to do that or how about a O.S. 4 stroke .70 or .90 any more suggestions.

Wagner the Saito .72 will turn a 13/6 APC @ 9,800 in flight tune all day long. The .61 2-cycle will turn a 11/7
about 11,500. The Saito has better throttle response, burns less fuel, and is is lighter. There is no comparison
for fun fly and 3-D type flying. As far as to big an engine I have. I once broke in a SuperTigre .90 were a .60
hsd been. I thought what the hay the bolt pattern and length and weight are the same why not. it did not crash the plane but the negatives outwieghed the positives. The only real plus was the verticle. The drawbacks were
torque off center whenever the throttle was slammed,and the longer prop getting in the grass. In normal flight it really wasn't much faster. Remember it takes ten times the horsepower to double airspeed. It worked to break in the engine, but flew much better when the .60 was back in place. It sounds like you want someone to tell you it's OK to put a .90 on that SIG. Truth is it will fly but all around performance will suck. Narrow you choice to
the .61 fx or the Saito .72 and you will be happy. Both of these will make that .46LA look bad.
later daveo

I built a somethin extra when sig first came out with them,and put an Irvine 53 on mine. Per the recomendation from the guys at SIG. They had been using them on they'rs. 60/90, and 4 strokers too heavy.

hi I have a buddy that got his SE this past summer and put a saito .72 on it and it is super cool to watch !! that satio 72 wieght is just over 16 oz and a ton of tork and power ! I have my SE nearly built and have a Irvine MK III .46 with a tower muffler ready to power it ! I have a 11x4 APC prop on it also but have read many threads on this.. And many guys seem to agree on the 12X3.75 APC !the power to wieght ratio they say the saito 72 has it ! Because of its light wieght ! and its a super easy running engine ! it will be on my list for my nexed project ! Just my $.02-.10 worth ! RJB