The connecting rods are forged steel: "Again, because of the loads." The pistons are made with a hypereutectic alloy
and designed with a thick crown area and use a special ring pack so that the boost pressure and heat generated by the turbo system can be handled.
The tribological properties can be attributed to the hypereutectic alloy
AlSi17Cu4Mg and the precipitation of primary silicon which protects the cylinder bore surfaces by means of wear-resistant grains.
Silver Anniversary paper, "Progress of 390 Alloy: From Inception Until Now." This hypereutectic alloy
became popular in the mid-century for engine cylinder blocks and has remained so due to its wear resistance, low thermal expansion and good elevated temperature service.
Comparing the results of the fluidity and impact strength tests, the study found that a hypereutectic alloy
containing more than 11% dendrite to ensure good impact strength should contain at least 6.2% aluminum.
At Porsche, a linerless V-8 block of a hypereutectic alloy
is cast by low-pressure permanent molding.
This research has established primary silicon-free hypereutectic alloys
with up to 17wt% silicon can be produced by directional solidifications.
Aluminum alloys with silicon levels above the eutectic point (hypereutectic alloys
) can be modified using phosphorus at an additional level of 0.003-0.006%.
"Semi-Solid Processing of Hypereutectic Alloys
Just as phosphorus (P) refines primary Si in hypereutectic alloys
, Al-P serves as a nucleant for the eutectic Si in hypoeutectic melts.
They also reported that [Al.sub.2][O.sub.3] and SiC inclusions in hypoeutectic Al-Si alloys nucleate pores, while in hypereutectic alloys
the particle is engulfed in the primary silicon phase.