Pipe length

[LarryConrad]

A few more pieces of the puzzle have arrived. Headers, pipes, and pressure fittings for my twin project. Those of you that run them, what is a good starting length for the CMB/AB .67 muffled pipe on a CMB VAC 91 ? Boat is a Eagle SGX 2. Props are 1667's from Andy's shop S/B and cupped to 5.8" Engines were prepped by Steve Wood, 50% Nitro fuel.

Larry

 

[JeremyEdge]

I ran 10-1/2" on that pipe with a 91 vac in my MicroBurst with a 1667 at .013 clearance.

But this was a single.

 

[Tom Foley]

I would run it at 11 - 11.5 with those props to break in then bump to 6.2 - 6.6 " on the props and you should see some great performance !! I'm not saying the 5.8"'s won't work as everyone's props are different but the VAC's will pull some prop !! I would also run 60 % but thats with my boat and I realize things change .

 

[Elias Vazquez]

Follow Tom's recommendations, as he runs 91VAC's on his twin "very" successfully.

Good luck with your new twin,

Elias

 

[JeremyEdge]

Yup Tom's twin is smokin.

 

[ALLAN YUEN]

better set up 11.5" on telescope CMB/AB .67 at your local then will play adjust -/+ .25" start " rich" use 50% because your new CMB91VAC need to break in five time out of tanks then look at "shine little wet" on glow plugs Good Luck!

 

[LarryConrad]

Thanks.