Paul,
In your opinion, which is the better install, 20b or a 13b?
I'm building a 3500 gvw Murphy moose. Eventually I'll put it on floats.
I'm looking for about 300 to 350 hp. I am brand new to rotaries but in the
last few weeks I have tried to absorb info from many different web sites.
Here is what I think I know.
The 13b would need to be far more modified; ported, turbocharged. It would
have more available parts for a rebuild.
The 20b, stock is at 280 hp. The apex seals are taller? And may not be as
good as some aftermarket 13b seals? 20b has more torque given the same hp
as a 13b. I've also read about aftermarket 3 rotor renisis builds with non
Mazda e-shafts (homemade).
There are so many different variables, I was hoping to get advice to gain
knowledge to eliminate some choices. Up to now I was vacillating between an
io-540 and a m-14.
Thanks, Paul lennemann.
The apex seals are interchangeable.
For that application a 20B would be much better. You can not have too much
power for a heavily loaded float plane. Ken Welter effectively uses
NOS to get his 3000 pound Coot on the step and out of the water in
less than 10 seconds with a 2 rotor.
I would use a 375 HP P-port 20B and use NOS for a few seconds to get it
on the step and out of the water. That should give you around 450 to
500 HP. Won't hurt the engine. Ken has burned hundreds of pounds
of NOS so far. Don't waste your time with a side port engine.
Paul Lamar
I couldn't agree more. ;-)
Mark S.
Lancair ES, N/A PP-20B
I came up with an answer for the higher force on a three rotor
slide throttle.
Due to three 2 inch holes the area of the intakes tubes is about
9 or 10 square inches. On over run (prop driving the engine) the engine
can develop as much as 15 psi in the intake runners. That puts a force
on the slide throttle plate of 150 pounds. The coefficient of friction of Teflon
is about .06 so the force on the cable can be up to 9 or 10 pounds.
Rather high.
If you use a 3 rotor slide throttle it might be a good idea
to use a throttle quadrant and give yourself a 2 or 3 to one
mechanical advantage. This will cut the knob force by up to a third.
The knob travel will be 4 to 6 inches instead of only 2.
Paul Lamar
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