A good friend of mine is running the M170 w/ a 17x12 and although the rpm's are not extremely high when tached on the ground, it just has enormous grunt in the air....hard to quantify...
Flyintexan: I was getting 7,750 on the 17x12 and 7,500 on a 17x13. I have the pipe set long (23.5" plug to first baffle) on 10% nitro, so I was´nt expecting much more.