Cast Iron Cylinder Blocks: Same Weight as Aluminum; Lower Emissions



WCX SAE World Congress Experience
Authors Abstract
In comparison to aluminum, Compacted Graphite Iron (CGI) iron has superior mechanical properties, enables the use of parent bore running surfaces and fracture split main bearings, and provides advantageous NVH, package size, cost, and manufacturing CO2 profiles. Despite these advantages, aluminum blocks have leveraged density, and therefore weight, differentials to make considerable gains in the small, in-line passenger vehicle sector over the last 30 years.
In order to demonstrate the potential benefits of CGI for small, in-line spark-ignition engines, the present study converted the cylinder block of a series production 1.2 litre three-cylinder engine from aluminum to CGI. Leveraging a novel design concept, with the running surface and load path constructed from high-strength CGI and the outer crankcase housing fabricated from durable, lightweight plastic, the assembled cylinder block achieved the same weight as the original aluminum block.
NVH analyses showed that the global flexural modes of the CGI cylinder block were 5% higher than aluminum block while the four main bearing cap modes were 18~40% higher, indicating potential NVH advantages for the CGI engine. It is further noted that the design of the CGI cylinder block was constrained by the need to maintain outer dimensions and bore-centers to facilitate engine assembly for durability testing. It is estimated that a clean-sheet design could have enabled a further 5% reduction in the weight of the CGI block.
With weight parity, and the successful completion of a 100-hour durability test, CGI has established a new benchmark for small, in-line passenger vehicle engines.
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Dawson, S., Ferrarese, A., and Marquard, R., "Cast Iron Cylinder Blocks: Same Weight as Aluminum; Lower Emissions," SAE Technical Paper 2023-01-0439, 2023,
Additional Details
Apr 11, 2023
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Technical Paper