pipe length?

Rick · Jul 18, 2003

I have a OS 80 in a cat hull using a Mac 13cc tune pipe and Octura X460 2 blade prop. Any advice on how long the pipe should be set at or a good starting point. Thanks Rick.

missbudpilot55 · Jul 18, 2003

Rick,

A good starting point is around 12 1/4" and work from there making it shorter untill performasnce falls off. Remember to richen your fuel mixture as you get shorter and reset the needle with each adjustment, it souldn't take but a couple of tries reducing the length by 1/8" at a time untill it really comes on song. Didn't say what percentage of fuel you were using, I run 50% in all of my engines from .45 and up.

missbudpilot55 · Jul 18, 2003

Rick

The way I determine my lengths is from the center of the cylinder casing to the weld or wide part of the pipe

rick · Jul 18, 2003

Thanks for the info. What are the popular fuels out their? I have used Red Max in the past. Not sure about 50% would 30% be good enough? Thanks Rick.

nitrotoys · Jul 18, 2003

They say a good starting point is about 12 or so. the higher nitro makes your pipe shorter also.

As far as nitro, Rule of thumb is the bigger the engine, lower the nitro. ANYTHING Over 30% in a .80 is just wasting it. I know some run 50 in there and they love them, it makes needle settings a pain with higher nitro, If you dont race your boat, and just play with it, run 15% in it and dial it in and you will be very happy with just 15%.

I run 10-15% in my 80 and runs just fine.

I ran 25 in it, and it ran faster, but was a pain to get on needle as its modded.

and you might want to just "try" a 462 or a x540. My mono seems to really like them two. May have to cut the leading edge and dia. down a bit. But give them a shot and play some with them, and see what i does for you.