What does '+0.5mm oversize' mean for these piston rings?

This means the rings are slightly larger in diameter than the standard size. They are intended for use when the engine's cylinder bores have been machined out by 0.5mm to account for wear or to achieve a specific clearance during an engine rebuild.

What is the purpose of the different ring thicknesses (1.2mm, 1.2mm, 2.8mm)?

The top and second compression rings are typically thinner for better heat transfer and sealing in performance applications. The oil control ring, at 2.8mm, is designed to scrape excess oil from the cylinder walls, preventing it from entering the combustion chamber.

Specifications

Brand: Manley Performance
Part #: 46925-1
UPC: 807298041209

Manley Subaru WRX EJ205/WRX STi EJ257 92.5mm Bore +0.5mm Bore 1.2mmx1.2mmx2.8mm Single Ring Set

Name: Manley Subaru WRX EJ205/WRX STi EJ257 92.5mm Bore +0.5mm Bore 1.2mmx1.2mmx2.8mm Single Ring Set
Brand: Manley Performance
SKU: manley-performance-manley-subaru-wrx-ej205-wrx-sti-ej257-92-5mm-bore-0-5mm-bore--t14-31125
Price: 48.65 USD
Availability: BackOrder

$48.65

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Manley Subaru WRX EJ205/EJ257 piston ring set. This +0.5mm oversize set is for a 92.5mm bore, crucial for engine rebuilds.

Key Features

Fits Subaru WRX EJ205 and WRX STi EJ257 engines.
Designed for a 92.5mm cylinder bore.
This is a +0.5mm oversize ring set.
Features a 1.2mm top ring, 1.2mm second ring, and 2.8mm oil control ring.
Manley Performance is a well-known brand for internal engine components.

⚠️ CA WARNING: This product can expose you to chemicals known to the State of California to cause cancer and/or birth defects or other reproductive harm. Learn more

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About this part

Product Details

These Manley Performance piston rings are built for a 92.5mm bore, specifically sized at +0.5mm oversize. This makes them a key component when you're rebuilding the engine in your Subaru WRX with an EJ205 or WRX STi with an EJ257 engine. Getting the right ring size is critical for proper cylinder sealing, which directly impacts compression and oil control.

The ring set features a specific configuration: the top ring is 1.2mm thick, the second ring is also 1.2mm, and the oil control ring is 2.8mm. This combination is chosen to work with the piston design and cylinder wall to ensure a good seal. Manley is known for making well-built internal engine components, and this set is designed to meet the demands of these performance Subaru engines.

Keep in mind that this ring set is not CARB approved and cannot be shipped to California. Always refer to your engine's specific service manual for installation procedures and recommended clearances.