Stage X EJ22 Piston Set - 2.35 Stroker

Forged pistons for the EJ22, built for a 2.35 stroker setup.

Why forged?

Forging is still the best way to make a piston, both for production and for strength. In some areas a piston machined from solid is marginally better, but the strength benefits of a forging far outweigh them. A correctly forged piston has an excellent grain structure. A fully machined piston has no true grain flow, because the material is used as it is cut from the bar. Forging creates optimal molecular alignment in the material, and combined with heat treatment this is what gives the piston its strength.

Precision

• Most of the machining that turns the forging into a piston is done on CNC (computer numerically controlled) machines.
• Pistons are measured at a constant 20.5°C, because they can expand by as much as 10 microns in sunlight. Tolerances can then be checked anywhere in the world, provided the same 20.5°C conditions are replicated.
• The skirt is designed and machined to give a profile that works most efficiently at full engine operating temperature. Skirt profiles are not round but elliptical, and barrelled along their length.
• The skirt is machined on extremely accurate machines that hold repeatability down to 5 microns.
• Every piston is individually weighed and batched to within 0.5 grams, so a set of four deviates by no more than 2.0 grams. On large orders, sets of four with only 0.1 gram deviation are not unusual.