Monobloc piston

1. A monobloc piston, comprising:

a piston body fabricated of at least two steel parts joined by a weld joint, said piston body having an outer annular ring belt wall extending between an upper surface of the piston body and a lower region of the ring belt wall spaced from the upper surface;

a plurality of ring grooves formed in said ring belt wall including an upper ring groove having a top edge;

a combustion bowl formed in the upper surface of said body portion and defined in part by a combustion bowl wall;

an inner annular support wall spaced radially inwardly of the outer ring belt wall and joined to said outer ring belt wall at an upper end by said combustion bowl wall and at a lower end by a lower wall and defining an internal oil gallery between said walls, a top of said oil gallery extends above said top edge of said upper ring groove;

a pair of depending pin bosses having pin bores aligned along a pin bore axis;

a piston skirt formed as one immovable piece with the pin bores having upper and lower surfaces; and

said piston having the following dimensional relationships:

ISMD=42-55% of BD, where ISMD is a mean diameter on the inner support wall and BD is an outer diameter of the ring belt wall,

ISW=3-8% of BD, where ISW is a sectional width of the inner support wall,

CH>53% of BD where CH is a compression height measured between the pin bore axis and the upper surface,

TLH>4% of BD, where TLH is a top land height measured between the top of the upper ring groove and the upper surface,

SL=30-80% of BD, where SL is a length of the skirt measured between the upper and lower ends of the skirt,

SW=2.5-6.5% of BD, where SW is a thickness of the skirt, and

GA=150-250% of BD 2 and GV=5-20% of BD 2 ×CH, where GA is the area and GV is a volume of the oil gallery.

2. The monobloc piston of claim 1 wherein said weld joint comprises a friction weld joint.