SinterCast has historically promoted CGI as a material that can provide environmental benefits. Today, it appears that most producers can satisfy Euro III and Euro IV emissions legislation without CGI and that CGI is primarily being used to achieve higher performance. Is there still an environmental benefit associated with CGI?


Shareholder, name withheld

The potential environmental benefit of CGI was first presented by SinterCast in 1992. At that time, we advocated that the diesel engine could provide improved fuel economy and thus reduced greenhouse gasses. In turn, the stronger material properties of CGI could allow diesel engines to operate at higher loads thus making them more competitive with petrol engines in terms of performance, noise and vibration. The ’link’ is that diesels are good for the environment and CGI is good for diesels. This is still true today and we can be proud that the diesel insight first presented in 1992 has been borne out by the dramatic growth in diesel engine sales over the past decade.

The environmental question has two parts: greenhouse gasses (CO2 and NOx); and, particulates. Unfortunately, the combustion conditions within an engine cannot be set to simultaneously minimise both of these pollutants. A combination of combustion optimisation and exhaust gas after-treatment is therefore required to satisfy future emissions legislations. The stronger properties of CGI can contribute to improving the combustion element by allowing higher pressures and temperatures and thus providing a more complete burn. Of course, higher pressures can also be achieved in grey iron or aluminium engines, however this requires the use of more metal (if the material is not as strong, the designer must use more of it) thus making the engines larger and heavier.

One further environmental benefit of CGI is its recyclability. A CGI engine block can be recycled to become any iron or steel product, with no restrictions. In contrast, aluminium is susceptible to contamination during use and recycling and must frequently be relegated to a product of lesser value after recycling. This ’step-down’ is not regarded as true recycling by strict environmentalists. Finally, the re-melting of a CGI cylinder block also requires less energy than the re-melting of an aluminium cylinder block.

Overall, we believe that a CGI cylinder block provides the best combined solution for, size, weight, performance, NVH and environment in both the passenger car and commercial vehicle sectors.