Some recent information has suggested that diesel engine performance may also be improved by reducing the compression ratio and operating at lower peak firing pressures. Does this affect the need for stronger materials such as CGI?


Shareholder, name withheld

The primary approach to improved diesel engine performance is through increased peak firing pressure. However, this approach puts considerable stress on the engine block, the cylinder head and internal components such as pistons and connecting rods. As the peak firing pressure exceeds approximately 170 bar, the durability of the aluminium cylinder heads becomes critical. Throughout the industry, designers are asking “where will the trend toward increasing P-max end?”

For SinterCast, we see the increasing P-max trend as a CGI opportunity, not only for cylinder blocks, but possibly also for cylinder heads, particularly for engines in the 3.0 to 7.0 litre size class which are typically used in larger vehicles that are less sensitive to weight increase.

For some other companies, the dilemma presented by increased firing pressures may present an opportunity to investigate alternative approaches to the diesel engine performance and emissions challenges. One such alternative is a combination of reduced compression ratio and lower peak firing pressure. This concept has the potential to reduce the mechanical loading and thus simplify the durability challenges. Other alternatives to solve emissions challenges include hybrid vehicles and fuel cells, or internal combustion engines that are based on a combination of petrol and diesel combustion concepts. These concepts use high compression pressures plus spark ignition to generate high specific performance (and high mechanical loading on the engine block) with relatively lower thermal loading on the cylinder head.

The demands on the automotive industry continually increase and novel ideas and proposals are constantly generated to meet the new demands. The trend toward higher peak firing pressures will continue for the next generation of high performance diesel engines, and many of the longer term prospects such as mixed petrol-diesel combustion cycles will also benefit from the superior properties of CGI.