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Diamond’s new, comprehensive range of nitrous pistons comes with all the bells and whistles.
Obviously, they are not designed to compete on price with entry-level conventional pistons. However, for those who need an entry-level piston today but may be considering adding nitrous or forced induction later, choosing the nitrous piston now might be the wiser plan.
The essential differences between the two are material type; the thicknesses of the crown, wall, skirt, and piston pin; the provision of gas ports; the depth of the top ringland, and the materials of which the top ring and oil control rings are made.
Though visually indistinguishable, Diamond’s conventional piston is made of 4032 aluminum while its nitrous counterpart is forged from 2618, a superior material when subjected to the higher cylinder pressures and temperatures of nitrous oxide. The difference in thickness of piston crowns, walls, skirts, and piston pins is more obvious—often ranging from 33 to 53 percent greater mass for nitrous use. Piston pins destined for nitrous engines are made of premium tool steel, H-13, rather than alloy steel, 8620, a favorite in naturally aspirated engines. Moreover, nitrous pistons are often endowed with a stiffening rib under each pin bore to fortify the skirts.
An important feature of a nitrous piston that doesn’t usually appear on a conventional street-strip piston is the adoption of gas ports. Characterized by a circle of small-bore holes, they penetrate to the depths of the first ring groove from the piston crown. Their purpose is to pressurize the inner edge of the top ring, forcing it out and making a tight seal on the cylinder wall.
Like the conventional piston, its nitrous mate uses a three-ring pack, but the top ring on the Diamond nitrous piston is placed further down from the piston crown (typically .300in compared with .200in conventional piston), to protect it from greater heat and higher pressures.
Finally, the top ring of a nitrous piston is often .020in thinner and .020in to .030in narrower and always made of a superior material than that of a naturally aspirated piston. Similarly the oil control ring has greater radial tension to prevent crankcase oil from entering the combustion chamber, particularly harmful to nitrous oxide engines.
Tags: DIAMOND, NITROUS, PISTONS
