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Forged Piston Kits

Cosworth forged pistons are engineered and manufactured in the UK using the same processes developed for their Formula 1 engines. Features include xylan anti-scuff skirt coatings, ultra-strong pins, polished domes, and anti-detonation bands. Each application uses a unique forging to minimize weight and ensure the strongest possible piston. Most applications use a proprietary Cosworth alloy similar to 4032, a high silicon alloy with a low expansion rate and high wear resistance making it ideal for extreme street performance as well as dedicated track applications. Piston kits are priced with rings. Replacement ring sets are also available separately.

Usually ships in 2 to 3 days.

Manufacturer: Cosworth

Applications:

  • Mitsubishi EVO 4-9 (4G63)
  • Mitsubishi EVO X (4B11)

What is the difference between the 4032 and 2618 alloys commonly used for forged pistons? 4032 is an aluminum alloy with a high silicon and nickel content. It has excellent wear and abrasion resistance and maintains its dimensional integrity over a longer life cycle. Additionally, it has a lower coefficient of thermal expansion allowing pistons to be installed with smaller piston to cylinder clearance resulting in a tighter combustion seal with less noise. These characteristics make it most suitable in high performance street driven applications.

2618 is an aluminum alloy with moderate copper and magnesium content but no slicon. It is a denser alloy with higher thermal conductivity and expansion rate. While these properties require it to be installed with increased piston clearance, it is beneficial in terms of reducing crown temperatures. 2618 has greater strength and ductility making it more forgiving to extreme conditions and detonation. Tensile strength of 2618 is approximately 64ksi vs. around 52ksi for 4032. However, its wear resistance and ring groove dimensional integrity suffers over the long term making it more stuiable for racing applications where shorter life cycles are anticipated and expected.

Which compression ratio should I choose? Higher compression ratios improve off-boost responsiveness and efficiency. However, raising the compression ratio increases the likelihood of engine knock and therefore fuel selection and tuning becomes very critical. Longer duration cams can allow the use of higher compression ratios because of the delayed intake valve closing reduces the dynamic compression ratio.