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The influence of graphite shape, pearlite content and chemical composition have been investigated to determine their effect on the machinability of compacted graphite iron (CGI). In the comparison to gray iron, the reduced sulfur content of CGI prevents the beneficial formation of a protective manganese sulfide layer on the cutting insert. This accounts for much of the difference in tool life during high speed continuous cutting. Beyond this critical mechanism, the machinability of CGI can be optimized by providing a consistent, low nodularity microstructure with a minimum of tramp elements such as titanium and chromium that form abrasive inclusions.

Although the superior properties of compacted graphite iron (CGI) are well known, its application to the series production of complex castings such as passenger car engine blocks has been precluded by the absence of a reliable foundry production technique. Despite the narrow chemistry range over which high quality CGI is stable, recent advances in cast iron foundry process control technology now serve as the starting point for a comprehensive CGI engine development programme at Adam Opel AG. The Opel CGI programme originated with the 2.5 litre V-6 DTM racing engine which now delivers 2.7 times more power and weighs 20% less than the standard grey iron production. Acoustical evaluations where then performed on identically designed 2.0 litre Family II engines to show that the audible noise level of the CGI engine was 1.1 to 1.5 dB(A) less than that of the grey iron engine.