Stage X Piston Set - Group N Rally 2001-2014 (V7+) EJ20

Forged piston set for EJ20 engines, 2001-2014 (V7+), Group N Rally specification.

Why forged?

Forging is still the best way to make a piston, both from a production point of view 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 within the material and, combined with heat treatment, this is what gives the piston its strength.

Precision and tolerance

• Most of the machining is done on CNC (Computer Numeric Controlled) machines.
• Pistons are measured at a constant 20.5°C, as they can expand by as much as 10 microns in sunlight. This way tolerances can be checked anywhere in the world under the same conditions.
• The piston skirt is designed and machined to give a profile that works most efficiently at full working temperature. The profile is not round but elliptical, and barrelled in length.
• The skirt is machined on extremely accurate machines that hold repeatability down to 5 microns.
• Each piston is individually weighed and batched to within 0.5 grams, so a set of four deviates by no more than 2.0 grams. Sets of four with only 0.1 gram deviation are not unusual.

Features of this set

• 1mm of extra material on the crown, which increases the compression.
• No lettering on the crown, so the piston can be used in a variety of applications.
• An extra 1 thou (0.001") of skirt clearance for high-load / high-power applications.