CP Piston & Ring Set Bore 99.5mm Size STD Compression Ratio 9.0 WRX / STI Subaru EJ257 2004-2021

Part #: SC7425. CP's forged pistons for WRX and STI are a game - changer. They offer excellent ring seal, higher vacuum, less blow - by, great durability, and more horsepower and torque across the power band. The peak horsepower stays strong throughout the life of the piston rings, thanks to lightweight forgings and CP's unique machining methods. CP is all about top - notch engineering. They use the latest forging techniques and CNC machinery, with strict quality control, ensuring a high - performance and reliable product every time. CP has some of the best quality control standards in the industry. It's part of Pankl Racing Systems, a high - tech racing group supplying parts to big - name teams and companies. You won't find better pistons for your EJ20 or EJ257. CP also offers optional coatings. The top coating reflects heat into the combustion chamber, increasing exhaust gas speed and scavenging ability. The skirt coating provides extra lubrication in extreme heat or heavy wear, reducing friction on the skirt. Coating options are for the whole set and add 4 - 6 weeks to the order time. Piston features include high - strength aluminum forgings, a super - lightweight design, full CNC machining and balancing to +/- 1 gram, an accumulator groove, double pin oilers fed from the oil ring, and wrist pins.

Using your CP piston and ring set is straightforward. First, make sure your engine is clean and ready for installation. Carefully place the pistons in the cylinders, following the orientation marks. When it comes to the rings, install them in the correct order as per the included instructions. Remember, this set is designed for WRX and STI Subaru EJ257 engines from 2004 - 2021, so don't try to use it in other engines. As for maintenance, regularly check the engine oil level and quality. The oil is crucial for lubricating the pistons and rings. If you've chosen the optional coatings, be aware that they add extra protection but may require a bit more attention. If you notice any unusual noises or a drop in performance, it's a good idea to have your engine checked by a professional. Also, follow the normal engine maintenance schedule recommended by Subaru for your specific model. With proper use and maintenance, your CP piston and ring set will give you great performance for a long time.