Hi i just thought i would post this up to help the people who cant visually tell the difference between factory rb30 turbo pistons and the factory na pistons. As you can see the turbo pistons (from an A8 motor) on the left are dished and this is to bring the compression ratio down to 7.8.1. The pistons on the right are standard non turbo rb30 pistons which are in the majority of vl's and in all R31 skylines except of course those that have had a vl turbo motor conversion. As you can see they have a raised surface that is much the same shape as the vl turbo pistons except that it is raised not dished. In fact when i put the na pistons upside down on top of the turbo piston i think it nearly fit perfectly into the dished area. The comp ratio for rb30 non-turbo pistons is 9.0.1. hope this helps.