Paul,
Sorry, the actual engine ports were 18 percent less area

than the tubes,

you know the other end of the manifold !
These figures were taken from the info/drawings given

with the exercise

to have the lower manifold cast - the one still in progress.
George (down under)

A lot of people open up the ports including Bruce Turrentine that
built Tracy's engine. Ed Anderson also ported his engine. Probably
others but those I know about for sure.

Paul Lamar

Paul,
Yep and they have 18 percent to play with except I'm now

wondering if

they have evn more - has anyone looked at the inside port area
facing the Rotar. I sure would like to know if this are is

identical to the

outside port area - I sure would like to know if ther is

some venturi

Also what do you consider appropriate for interference and

parasite drag

for the manifold tubes - I notice you are considering this ! say In
percentage terms ie. educated guess.
Also (in percentage termes) the restriction of the

butterfly in the Throttle

Body.
The reason I ask is that by my calculations the throttle

body can be 2.75 "

with an 18 Percent reduction  (port area) which = 2.25 "

plus the other

factors such as mentioned above plus opening -up the inside

port ares.

This approach might give a better understanding to everyone on what
theThrottle Body dimensions are for each configeration.
Also it might explain why some people are getting away with

less than

a 3" Throttle Body. Excepting the other reasons you metioned in
specific cases.

Sorry to be a pain, it's just something I've been wondering about,
BTW what size Throttle Body does Mecanair run.
George (down under)

Here is a drawing I made up of a 6-port 13B intake ports. The center housing
port is in red, end housings in black. Drawing was made on Turbocad using
graph paper as a "digitizer" and transferring coordinates to CAD. Turbo cad
computed the area.
I come up with 5.07 sq. in total port area for 2 rotors, about the same area
as a 2 1/2" throttle body. Of course the throttle body does not need to
match the port area, it's just that the velocity and pressure loss would be
lower if it is larger than the port area.

Chuck Dunlap

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