Taken from Towerhobbies.com .....

Engine: .40-.46 (6.5-7.5cc)(2-stroke)
OR .56-.65 (9.2-10.6cc)(4-stroke)


Do you think a Saito .72 or an OS .70 is too much power for a Sig Somethin' Extra? I am currently running a Thunder Tiger .46 Pro on it with an 11 x 3 prop.

The Saito 72 or OS 70 4 strokes will be fine. You will be at the upper end of the power requirements. You will find that the 4 stroke engines of that size MAY be a little over powered for the plane (depending on the weight). You will be running a larger prop, so make sure you have adequate ground clearance (you should be ok on that). You will most likely be running a 13x6 prop on those engines vs an 11x6 you are presently using.

My Saito 72 provides power ABOUT equal to a good running/hot 53 to an average/semi tired 60.

You fuel consumption will be a lot less - figure an additional 25%+ flying time compared to the 46.

Don't forget to rebalance the plane

Good luck. I think you will enjoy the sound of the 4 stroke much more than the 2 stroke. Remember, if the engine is not putting out smoke, you are most likely running it too lean.

Hope this helps.

I have a Saito 56 on mine and love the combination. I think the OS may be a bit heavy for this airframe. The trade off of power may not be worth it. The Saito 72 would be a better choice if you need 3D power. Prop clearance may be an issue.

Difficult to believe you can get that TT .46 to perform very well with a 11X3 prop though. Have you tried a bigger pitch like a 11X5? Or 12.25X3.75?

I did a test yesterday at the field. I put on about 6 different props, ranging from 10x5's up to 11x6, and I liked the 11x3 the best. I am not a speed demon, but do like the vertical pulls from the 11x3 the best.

Rich, the saito .72 is my favorite engine for .40 size planes. They are lighter than most .46's and a heck of a lot more torque. The saito .72 would be perfect for your SE. I have a sig se with an irvine 53 on it. I am running a 12" prop and have only about 1" of prop clearance with the stock landing gear. If I was going to put the saito .72 on this bird, I would check out a new landing gear to give you the required clearance for the 13"-14" props. A good place to get one of these gear is: www.tntlandinggear.com, part number LG-177

Already have the dubro fiberglass gear under it. Same gear that I used for my LT-40 taildragger conversion, but painted it gloss black.

Clearance isnt an issue anymore

Go for it. The Saito would be just peachy in that plane. You'll love it.

Mark Shuman

I think I will start saving up for a Saito 72. Might go with the FA-72 Golden Knight since it does match the colors of my plane.