Under the Hood: DodgeSRT-4
The turbo pistons, cast by Mahle from a eutectic aluminum alloy, have a shorter pin height (the distance from the wrist pin to the top of the piston) than the naturally aspirated piston on the left, lowering compression to 8.1:1. The turbo pistons also use full floating wrist pins, where the naturally aspirated pins are pressed into the piston. Full floating pins cause less friction and better handle the higher cylinder pressures. The skirts are coated with Mahle's Grafal low-friction coating for, well, less friction. The top compression ring groove is hard anodized (that's the gray band) to prevent the hot top ring from microwelding itself to the piston.
As with all modern engines, the top ring land has been made as short as possible to reduce emissions caused by unburned fuel hiding in the crevice between the ring land and the cylinder wall.
The smaller ring lands (4mm in this case, compared to 8mm on the old 1990 2.5-liter Chrysler turbo) can't survive as much detonation, but modern engine management makes that detonation much less likely anyway.
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