freebird1

Hi all

I have a predator with a O.S. 46 AX. I also have a Viper with a 40 Q-500 Rossi. The Predator is much slower than the Viper. The Predator has a long Mac tune pipe with a APC 8.75x8.75. Should I change prop size, or is the drag of the pipe the problem.

Thanks

Freebird

Crazy4Flight

My Feedback: (540)

change the engine, the OS 46 FX/AX are good sport plane engines for about 100.00. But the are not speed plane engines with or with out a pipe.

As you stated: your Rossi is a Q-500 THAT is the difference between your planes

daven

My Feedback: (1)

I am not sure what your pipe is tuned for, but a stock muffled O.S. AX with a 10x7 prop should be able to take the predator over 120 mph. I would try a couple different props with the muffler to see if you are in the right RPM range.

freebird1

I think you are right Crazy4Flight. Daven, what is a good RPM range for the O.S. I get about 16,5K with the Rossi and an APC 8.75x8.75, and the viper is smoking. The viper in my opinion is the better built of the two, howevery the Predator bleeds off speed better than the Vipor. We do a little pylon to pylon thing at our club and this racer would be perfect for that (500'). We also do a flat out race from the end on the field to the other end for fun.

daven

My Feedback: (1)

I am only familiar with the stock muffler, but from what I have read and seen, the AX develops its best horsepower at roughly 14,200 rpm.