GreekGod
06-01-2007, 02:25 PM
Barry Rabtonick posted on the FordFE.com forum, on Cast vs. hyper pistons:
<TABLE cellSpacing=0 cellPadding=1 width="100%" border=0><TBODY><TR><TD style="BACKGROUND-COLOR: #ffffff" align=left bgColor=#ffffff>Cast vs Hyper<!-- google_ad_section_end -->
</TD><TD vAlign=top align=right>June 1 2007, 7:45 AM </TD></TR></TBODY></TABLE><TABLE cellSpacing=0 cellPadding=1 width="100%" border=0><TBODY><TR><TD style="PADDING-LEFT: 15px">
<!-- google_ad_section_start -->You have two inter-related issues at play - manufacturing method and alloy. Forged and cast are the two manufacturing methods. Hypereutectic or eutectic are the rough alloy designations, with innumerable variation of each being available. At this time I am not aware of any commercially available forged hypereutectic pistons - so all hypers are cast, and thus limited to the material density and ductility limits inherent in the process.
Actually a plain eutectic cast piston is less likely to crack than a cast hypereutectic under duress beyond each product's limit.
The hyper's added silicon is in the form of hard nodules - each of which serves as a stress point. The silicon makes the alloy harder, which the OEs like because the ring grooves and skirts will not wear - good for high mileage life and emmission durability.
A hyper will have a higher fatigue and tensile strength limit, but a less desireable failure mode once those limits are reached/exceeded.
Forged pistons are all eutectic (having +/-11% silicon - commonly 4032) or hypoeutectic (no silicon - race oriented 2618). They will be at least equal and usually far better product by all measurements except cost and very long term wear resistance (especially true for 2618).
Barry Rabotnick
Survivalmotorsports.com<!-- google_ad_section_end -->
</TD></TR></TBODY></TABLE>
<TABLE cellSpacing=0 cellPadding=1 width="100%" border=0><TBODY><TR><TD style="BACKGROUND-COLOR: #ffffff" align=left bgColor=#ffffff>Cast vs Hyper<!-- google_ad_section_end -->
</TD><TD vAlign=top align=right>June 1 2007, 7:45 AM </TD></TR></TBODY></TABLE><TABLE cellSpacing=0 cellPadding=1 width="100%" border=0><TBODY><TR><TD style="PADDING-LEFT: 15px">
<!-- google_ad_section_start -->You have two inter-related issues at play - manufacturing method and alloy. Forged and cast are the two manufacturing methods. Hypereutectic or eutectic are the rough alloy designations, with innumerable variation of each being available. At this time I am not aware of any commercially available forged hypereutectic pistons - so all hypers are cast, and thus limited to the material density and ductility limits inherent in the process.
Actually a plain eutectic cast piston is less likely to crack than a cast hypereutectic under duress beyond each product's limit.
The hyper's added silicon is in the form of hard nodules - each of which serves as a stress point. The silicon makes the alloy harder, which the OEs like because the ring grooves and skirts will not wear - good for high mileage life and emmission durability.
A hyper will have a higher fatigue and tensile strength limit, but a less desireable failure mode once those limits are reached/exceeded.
Forged pistons are all eutectic (having +/-11% silicon - commonly 4032) or hypoeutectic (no silicon - race oriented 2618). They will be at least equal and usually far better product by all measurements except cost and very long term wear resistance (especially true for 2618).
Barry Rabotnick
Survivalmotorsports.com<!-- google_ad_section_end -->
</TD></TR></TBODY></TABLE>