CP Pistons SC8705-6 HD Forged Piston & Ring Set 82mm 11:1 CR for BMW/Toyota B58

Vehicle Fitment

• 2020-2026 Toyota GR Supra (A90/A91, 3.0L I6 Turbo B58B30)
• 2019-2026 BMW M340i (G20/G21, 3.0L I6 Turbo B58B30)
• 2021-2026 BMW M440i (G22/G23/G26, 3.0L I6 Turbo B58B30)
• 2022-2026 BMW M240i (G42, 3.0L I6 Turbo B58B30)
• 2019-2026 BMW Z4 M40i (G29, 3.0L I6 Turbo B58B30)
• 2019-2026 BMW X3 M40i (G01, 3.0L I6 Turbo B58B30)
• 2019-2026 BMW X4 M40i (G02, 3.0L I6 Turbo B58B30)
• 2016-2019 BMW 340i (F30/F31, 3.0L I6 Turbo B58B30)
• 2016-2020 BMW 440i (F32/F33/F36, 3.0L I6 Turbo B58B30)
• 2017-2020 BMW 540i (G30/G31, 3.0L I6 Turbo B58B30)
• 2017-2019 BMW 640i GT (G32, 3.0L I6 Turbo B58B30)
• 2016-2019 BMW 740i (G11/G12, 3.0L I6 Turbo B58B30)
• 2019-2026 BMW X5 xDrive40i (G05, 3.0L I6 Turbo B58B30)

Fitment Notes

• Designed exclusively for the BMW/Toyota B58 3.0L inline-6 engine platform
• This is the Heavy-Duty (HD) forging variant - not the standard SC7705 shelf piston
• Not compatible with the BMW B48 2.0L 4-cylinder engine (see SC7706-4 for B48 applications)
• Fits both B58 Gen 1 and B58TU (Gen 2) variants
• 82mm bore is standard bore size - no overbore required
• Requires professional installation and engine assembly by a qualified builder

Features

• Heavy-duty forging designed to support 1,200+ wheel horsepower
• Forged from high-strength 2618 aluminum alloy for superior durability under extreme heat and detonation
• Fully CNC machined to exacting tolerances for precise fitment and optimal combustion
• Accumulator groove reduces ring flutter and improves seal under boost for increased power
• Dual forced pin oilers provide double the oil supply to the wrist pin for enhanced lubrication
• Radiused valve reliefs for compatibility with aggressive camshaft profiles and oversized valves
• Pin lock grooves included as a standard feature for secure wrist pin retention
• Each piston balanced to within one gram for smooth, vibration-free operation at high RPM
• Pin fitting final hone performed at the factory for precise wrist pin bore tolerance
• Matched and balanced set of 6 pistons for consistent cylinder-to-cylinder performance

Specifications

• Part Number: SC8705-6
• Engine Application: BMW/Toyota B58B30 3.0L Inline-6 Turbo
• Bore Diameter: 82mm (standard bore)
• Stroke: 94.6mm
• Connecting Rod Length: 148mm
• Compression Ratio: 11.0:1
• Compression Height: 33.25mm
• Wrist Pin Diameter: 22mm
• Piston Material: 2618 Forged Aluminum
• Ring Set: Included (PVD coated)
• Piston Type: Heavy-Duty Forging
• Power Rating: 1,200+ WHP
• Set Quantity: 6 Pistons

Included Components

• 6x CP-Carrillo Heavy-Duty Forged Pistons
• 6x Matched PVD-Coated Piston Ring Sets
• 6x Lightweight Wrist Pins
• 6x Pin Locks

Product Description

The CP Pistons SC8705-6 is a heavy-duty forged piston and ring set engineered specifically for the BMW/Toyota B58 3.0L inline-6 turbocharged engine. Unlike the standard SC7705 shelf piston, the SC8705 uses a dedicated heavy-duty forging designed to withstand cylinder pressures exceeding 1,200 wheel horsepower, making it the choice for serious race builds, high-boost turbo setups, and methanol-fueled applications where standard pistons reach their structural limits. Forged from 2618 aluminum alloy, these pistons offer the ductility and thermal resistance needed to survive extreme combustion events without cracking or failing.

Every piston in the SC8705-6 set is fully CNC machined and incorporates features that are typically reserved for custom orders. Dual forced pin oilers deliver enhanced lubrication to the wrist pin under high load, while the accumulator groove captures combustion gases behind the top ring to reduce flutter and improve sealing - translating directly to more power and more consistent cylinder pressure. Radiused valve reliefs ensure clearance for aggressive camshaft profiles and oversized valves, and each piston is balanced to within one gram of the others for smooth, harmonious operation across all six cylinders at elevated RPMs.

The SC8705-6 is a direct fit for the B58 engine at the standard 82mm bore size and works with the factory 94.6mm stroke and 148mm connecting rod length. It is compatible with both the original B58 Gen 1 found in 2016-2019 BMW F-chassis models and the B58TU (Gen 2) used in the Toyota GR Supra A90/A91, BMW G-chassis M340i, M440i, M240i, Z4 M40i, and X3/X4/X5 M40i models. This set includes matched ring sets, lightweight wrist pins, and pin locks - everything needed for a professional engine builder to complete a bottom-end assembly built for four-digit horsepower.