GReddy is offering this JE billet piston upgrade for their VR38DETT engine packages. A properly designed billet piston will be lighter and stronger than a forged piston, it will also cost more. However, if you are looking for more than 1000hp out of a VR38 for your GTR, this would be a good option. They are a $1000 upgrade on the 3.8-4.4 liter engine packages. Check the information below from GReddy.
We have teamed up with JE Pistons and Dynamic to develop the strongest pistons sets possible for extreme monster builds. The design and development took almost a year to complete but it was worth the wait! We took our VR block with our stroker cranks to JE Pistons back in April of last year to start development of forged and billet pistons sets for our engine program and we requested JE to perform Finite Element Analysis (FEA) for development of these pistons to test the stress and fatigue on a computer model before production. Each billet pistons are machined out of a block of high quality 2618-T6 aluminum. 100% CNC machined part means every surface are machined allowing for all unnecessary weight to be removed to keep the piston lighter but stronger. The piston features internal and external struts for improved durability and strength.
These billet pistons are not for everyone, but if you are targeting over 1000HP, you might want to consider these. Why billet over forged? To make forged pistons as strong as these billet pistons, they will be heavier which will affect the response and acceleration. By machining every surface, billet pistons can achieve the highest uniformity of material thickness on skirts and general body, which results in improved heat dissipation caused by stress concentrations experienced in high boost / high power engines. This is not possible with plain shaped forgings on a high production pistons.