Cluster systems built mainly from commodity hardware components have become more and more usable for high performance computing tasks in the past few years. To increase the parallelism for applications, it is often desirable to combine those clusters to a higher lever, commonly called metacomputer. This class of high performance computing platforms can be understood as a cluster of clusters, where each cluster provides different processors, memory performance, cluster interconnect and external networking facilities. Our project called MetaMPICH provides a transparent MPI-1 implementation for those inhomogeneous cluster systems. While this feature of transparency makes porting existing MPI applications to metacomputers quite simple, the slowest network connection and the slowest processor will dominate the performance and scalability due to the lack of opacity. This paper describes our approaches to adapt iterative, grid based simulation algorithms to the structures of such heterogeneous coupled clusters.