I have both of these engines NIB and plan to use a 40 size FS on a future CL stunt/sport build. Probably a profile warbird model. For those that have direct experience with these engines, which one is considered to be more powerful? If I was guessing at this point, the warbird model will weigh in the neighborhood of 48 oz, with a wing loading around 14.

The Saito FA-40a is interesting as it is a full 2 oz lighter that the OS 40 Surpass FS.

Thanks in advance.

I don't have the Surpass 40, but the Saito FA-40a is a lovely engine, very impressive power! Comparable or better than most 46-size two strokers. You are a lucky guy!

I have/had three of each.
The SAITO 40 is a wonderful piece of engineering, perfect for our needs.
I consider the Supass 40s, on the other hand, to be "Reverse Excedrin"* engines.
Of the three I HAD, the performance was  nowhere near that of the SAITO.
Each one was carefully broken in EXACTLY according to OS instructions.
Inconsistent runs, broken crank pin, difficult starting, etc.
One of my close friends had one with which he experienced similar issues.
I've owned over 100 4 cycle engines including ENYA, OS, SAITO, WEBRA and HP and Morton.
I still have well over 60.
In defense of the OS, I've owned every one from the 20 up to the 70 and the only one that had issues was the Surpass 40.

Bob Z.

*doesn't cure headaches, it causes them!