OpenFOAM 2.1.1 GGI / AMI Parallel Efficiency Test

A 2D incompressible turbulent transient simulation featuring rotating impellers was performed on a varying number of processors to test the parallel capability of the AMI feature in OpenFOAM. The size of the case was small, about 180,000 cells total. This ensures that memory would not be a bottleneck. The exact same case was run on different numbers of processors. The computer used had 2 x AMD Opteron 2378 (2.4 MHz), for a total of 8 cores. I am not sure what CPU specs are relevant in this case, so you can look it up. Let me know what other specs are relevant and why in the comments.
The following are the results:

 The efficiency is the most revealing metric here. There seems to be a serial component to the AMI bottle necking the performance. I will post some more results done on a different computer shortly.