Pistons (See Figure 2-17) are cast aluminum with:
• A ni-resist full top ring groove.
• 2-piece oil control ring.
• “ Full floating piston pin” .
The full ni-resist insert-molded cast iron full groove protector is for high temperature strength and improved fatigue life. Ni-resist is a metallurgical term describing a cast iron consisting of graphite in a matrix of austenite. Austenite is a non-magnetic solid solution of carbon in gamma-iron. This version contains significant amounts of nickel and chromium. It has high resistance to growth, oxidation and corrosion. It has a high bonding ability to aluminum, and thermal ability (high dissipation rate of aluminum).
The “ full-floating ’ piston pin concept is used to eliminate pin-to-boss scuffing and to promote uniform pin loading through pin rotation. This happens by using the film thickness of the oil, that the pin is suspended by, and rotating in to increase loading and surface area. The film thickness is also used to absorb some of the downward thrust.
