Description Reviews CP Piston & Ring Set for Mini Cooper S N18 1.6L - Bore (77mm) or (77.5mm) - CR (10.5) - Set of 4 w/ w/rings & hardware. Note: The 77.5 mm Bores only come with the Skirt Coating High performance, forged pistons by CP Carrillo for R55, R56, R57, R58, R59 MINI Cooper S models only. Includes a set of 4 pistons, rings, and wrist pins and will be compatible with oversized valves. When building the bottom end of your N18 1.6L engine, it is essential to have a superb piston that can handle boost and maximum horsepower. CP is a division of Pankl Racing Systems, a high-technology racing group supplying engine and suspension components to numerous Formula One, F3000, IRL, CART, World Rally Racing teams and to such elite companies as Ferrari and Porsche. CP forged pistons feature superb ring seal, higher vacuum, lower blow-by, greater durability and increased horsepower and torque through the power band. Better yet, peak horsepower is retained through the life of the piston rings. This is achieved by lightweight forgings and CP's exclusive machining techniques and processes. CP's commitment to racing is reflected in every piston they produce. CP is dedicated to superior engineering, utilizing the latest forging techniques and CNC machinery and backing it up with rigorous quality control; it makes for a top-notch product every time that emphasizes performance and reliability. CP has some of the highest quality control standards in the industry. Coating Options: Skirt Coat / Moly Dry Film Coating: This is the most popular 9and highly recommended) coating. The application of molybdenum to the piston skirt is used to reduce friction between the piston and the cylinder during engine operation. It also helps during cold start ups and high temperature operation where a substandard oil barrier on the cylinder wall could exist. This option will really help with wear and overall engine noise. Ceramic Crown Coating: This coating reflects heat into the combustion chamber and away from the piston crown, while lowering piston temperatures for increased part life. The engine can experience improved combustion and performance as a result of heat being reflected back into the fuel charge. Features and Dimensions: Bore (in): 3.307 in. or 3.327 in. Bore (mm): 77mm or 77.5 mm Piston Style: Dish, with no valve reliefs Piston Material: Forged aluminum Compression Distance (in): 1.043 in. Piston Head Volume (cc): +1.70cc Wrist Pin Style: Press-fit or floating Pin Diameter (in): 0.827 in. Gapless: No File Fit: No Top Ring Thickness: 1.0mm Top Ring Material: Steel Second Ring Thickness: 1.2mm Second Ring Material: Cast iron Oil Ring Thickness: 2.8mm High-strength aluminum forgings Super lightweight design Fully CNC machined and balanced to +/- 1 gram Include wrist pins Accumulator groove included Double pin oilers, force fed from oil ring High performance rings Pick grooves for easy lock removal Custom skirt and barrel design Special noteworthy features: Anti-Detonation Grooves: Grooves that protect the top ring by disrupting detonation waves. These grooves limit the piston/cylinder contact during high temperature and RPM and are also known as contact reduction grooves. Accumulator Groove: A V-shaped groove machined in the second ring land to collect excess blow-by between the top and second ring. This groove collects residual gases during combustion and alleviates top ring flutter while increasing ring seal. CP groove: Stands for Constant Pressure Groove. This groove works as a channel on the lower part of the top land that equalizes pressure to the back of the top ring groove. When used in combination with lateral gas ports, the CP groove helps keep gas ports clear of carbon buildup. In addition, the CP groove prevents the top land from smudging into the top ring if the land rubs the cylinder bore. Double Pin Oilers: In conjunction with their dual fed reservoir add twice the amount of oil from the cylinder wall to the wrist pin. Cam and Barrel:Extensive research and development has been done to find the optimum skirt shape for each piston. Having the correct cam and barrel on a part promotes the following: tighter clearances, less noise, better ring seal, more power, and durability. Depending on the forging and application, different cam and barrel profiles are utilized for maximum performance. For instructions on piston install, please go here. Note: Currently we try to keep 1-2 set in stock with a Skirt coating and/or Top Coating. But other coating can be special order. Lead time can be 5-6 weeks currently, and coating can be an extra 1-2 weeks..