RSA 5 vs RSA 10 on IO540

[chazking]

Which is the better fuel servo for an IO 540? RSA 5 (FM200) or RSA 10 (FM300)? I'm told the 540 "breaths" better with the 10 (FM300) & that makes the 540 "more efficient." Where does the truth lie?

[Toobuilder]

Since the RSA-10 and -5 are both found on 540's and 360's, I've often wondered this as well.

[rocketbob]

There is less of a pressure drop across the venturi of the -10 than the -5. That said to take advantage of the additional airflow capability you should go with the cold air sump if you want to go with a -10. The -10 will not bolt to a stock 540 sump.