In the very hypothetic case that I would like to replace one of my extremely powerful and reliable 46AX for an OS 4-stroke... what model would give me the same performance? My planes are a Bridi Advance trainer and a low wing design (very similar to a Sig 4* 40) and both have unlimited vertical performance, something that I wouldn't like to exchange.

Additional information: I use MA 11x6 and APC 11x6, with Byron 5% fuel.

All coments helps. Thanks

A OS 70 Surpass II would serve you well.

The Bridi trainer would be a little crowded up front for a 4 stroke? They were designed before the 4 stroke was. It could be set up a little different and made to work.

The engine would fit a 4 Star 40 fine but don't know about your plane?

The OS FL 70 and Ultimate 70 have not been as trouble free as the Surpass II version.

Enjoy,

Jim

Martin:

Consider the Saito FA-72. It's lighter than the OS 70, or if yu want more power go for the FA-82 which is not only more powerful, it's lighter yet.

Bill.

Should it be O.S. only?
O.S. are excellent engines, but if you want a lot more power, reliability and a kind of status, try the supercharged YS 63S FZ, you won´t be dissapointed at all.
Those are really powerfull engines.

RV

Bill, Jim, RV, thanks to all of you.

It is not have to be an OS engine. My question said OS just because originally I posted it in the OS forum, and because I've been happy with my 6 OS's so far....

This would be my first 4-stroke, an my main concern is the compared power. For us "newcomers" is kind of confusing. I buyed the concept of "more torque at low rpm", but, frankly, I don't understand it (and I already read Bax's article on the fact).

Even to make my own numbers is difficult, since not all manufacturers detailed this information, and it is very subjetive anyway. So I figured I could get some help from the forum about this very difficult subject (and I did, thank you very much again).

Jim, you're right, Joe Bridi did not think of a 4-stroke, it would be difficult to get it in there. There is plenty of room in my sport model thou..
Bill, weight is first on the list, so I will consider Saito as well
RV, the YS63 was the first one I noticed, since I read in another forum that it has quite the same power of my 46AX, so from my little knowledge, it looks that I wouldn't be wrong this way...

Keep posting your thoughts, it is great to have you there.

Thanks and regards,

There's a guy at the flying field with a Y-S 63 in a Sig Somthin Extra. Seems to fly fine.Does a fair job on vertical performance.

Enjoy,

Jim