I am stuck on 1 7/8 [ID] runners. Sames as the Lemans engine.
Why reinvent the wheel. I know it rolls :)

Paul Lamar ...No rotor no motor.

*****
Hi Paul,
I can't find my torque/power figures for the LeMans engine; what rpm
was it getting max figures at?
I'm thinking 1.75 in runners might suit our rpm better.
Ta, Dave McC

There is a big difference in the port area.
1.75 OD is  is really 1.625 ID. Area is 2.07 square inches.
2 inches OD is 1.875 ID. Area is 2.76 square inches.
My guess is HP would be less than 200.

Here are the Lemans curves.
-- 
Paul Lamar ...No rotor no motor.

Paul

Are you sure about that 1 7/8" figure?  A drawing and test results I
received from the engineer that actually designed the Leman's manifold shows
the ID at 50mm. or 1.968 inches or 20 square centimeters.  His report was
done at on 2-22-1989.

Max power is about 664 PS at 9,000 rpm. This four rotor engine slightly pre
dated the wining Lemans engine but I can't imagine Mazda decreasing the
manifold size diameter and getting more power out of the next version
engine.


DougFir

I would like to have a copy of that report Doug if it is in English.

1.968" - 1.875" is .093 or 93 thousands. We could go to .035 wall SS tube
which has an ID of 1.91 or only 1.968" - 1.91" or .058'"or 58 thousands
difference. I got it as close as I could at the time.

Burns Stainless now offers 2-1/8" OD .065" wall
6061 same center line radius so that would give us 2" ID. Perhaps
its worth a try.  We would wind up with a little less support for
the apex seal as it passes over the intake P-port.

We got about 243 HP with a Weber 58 mm carb at 7000 RPM and they
got 295 HP with a slide throttle at 7000 RPM. The p-port engine
with two 48 MM (1.889") Mikunis might do better than the Weber as there
is less obstruction in the runners however the throats are smaller.

It remains to be seen what HP we will get with our slide throttle.
We are about to find out as Mark Suspinski should have his engine
running this coming week end.