Still A Possibility For Light Duty Diesels
At this years' ASME Internal Combustion Engine Division 2013 Fall Technical Conference, the idea of using steel pistons was spotlighted as a very real possibility for use in light duty diesel engines...
Thanks to OE and aftermarket piston supplier Mahle, a number of papers were presented regarding engine design, one of which suggested steel pistons could become commonplace for light-duty diesel engines. Although (the paper went on to say), the primary driver behind engine design is fuel consumption and emissions, rather than component strength. According to an article published on dieselnet.com, the Mahle paper re-stated the advantages you may or may not have already read about in the magazine (here, and/or here).
It went on to read: "Steel has some advantages such as a lower coefficient of thermal expansion that can be exploited to reduce friction—especially if the alternative aluminum piston goes into an overlap condition (i.e., the maximum radius of the piston exceeds the radius of the cylinder bore). Other benefits of steel pistons include the potential for smaller compression height and lower reciprocating mass, a reduced top land crevice volume that can yield lower cold start CO emissions and lower rates of deformation that can allow piston rings to seal better and reduce blow-by."
Another paper from Mahle stated that a new wrist pin design with an oval wrist pin bore could serve as a way to solve wrist pin joint ticking (which often occurs during engine warm-up).