Hi,
Finally, got the rotor in the mail. Thanks to Paul. (Is it RX8 rotor? I remember that You mentioned that pocket and faces are machined. On this one pockets a left as cast.)
I agree totally with what Paul and Rob are suggesting.
Next steps:
1) Disassemble it.
2) Cut in two halves.
3) Scan it.
4) Create a valid 3D model of standard Mazda rotor.
Here I will need help from Rob.
Rob, as I understand You've got all the math to model the rotor faces. If I remember correctly You're working with Pro/E. Is it possible that You model outer geometry (faces) and send me the file (native Pro/E or any common - Parasolid, Step or IGES). Modeling the faces out of scan data is not the best idea IMHO.

5) As Rob mentioned "Cast Ti has anywhere
from a 1/2 to a 1/3 less thermal conductivity versus cast irons. 40
percent less density, half the expansion rate, double to triple the
tensile strength but anywhere from equal to half the modulus of
elasticity. If i were just looking at it, without changing any
dimension(based on modulus vs. tensile) it would be about 40 percent of
the weight of the rotor."

If I remember it right Mazda rotor is made out of ductile iron. Its properties:
Elastic Modulus    120000    N/mm^2
Poissons Ratio    0.31   
Shear Modulus    77000    N/mm^2
Thermal Expansion Coefficient    1.1e-005   
Density    0.0071    g/mm^3
Thermal Conductivity    75    W/m K
Specific Heat    450    J/kg K
Tensile Strength    861.695    N/mm^2
Yield Strength    551.485    N/mm^2


Now for the Ti cast rotor I'm planning to use VT20L which was designed for extended work at 500C.
  Fe     C      Si       Mo    V    N       Al    Zr       O         H
<0.3   <0.1  <0.15    2     2.5 <0.05    6     2    <0.15  <0.012

Elastic modulus    123000    N/mm^2
Poisson's ratio    0.33   
Shear modulus    46000    N/mm^2
Thermal expansion coefficient    9e-006   
Mass density    0.00465    g/mm^3
Thermal conductivity    7.8    W/m K
Specific heat    500    J/kg K
Tensile strength    1160    N/mm^2
Compressive strength    1170    N/mm^2
Yield strength    1070    N/mm^2
Hardening factor (0.0-1.0; 0.0=isotropic; 1.0=kinematic)    8.5e-007    N/mm^2

Advantages that we may have:
Strength =   134.6%
E modulus = ~ 100%
Density =  65.5%
Thermal conductivity =  10.4%
Thermal expansion =  82%

More than that at high temperatures  mech. prop. advantages will be higher.

Anyway as Bob mentioned we can  safely assume 30% weight reduction of rotor assembly. I agree with Rob that revving the engine 20000RPM may cause all sorts of problems. But revving the  3 rotor engine to 12 - 13,000 RPM sounds realistic to me.

Now, what's the current thinking about feasible price for a 7 - 6.5lb Titanium rotor? We're not talking about mass production but high power applications.

Thank You
Ted