Wiseco K590M84 Forged 84.00 mm Pistons for 1994-2005 Mazda Miata/Protege 1.8L

Vehicle Fitment

• 1994-2005 Mazda Miata / MX-5 (BP-ZE / BP-VE, 1.8 L, 16V)
• 1999-2000 Mazda Protege (BP, 1.8 L, 16V)

Features

• Forged from high-strength 2618 aluminum alloy for durability
• ArmorGlide® skirt coating to reduce friction and resist seizure
• Strutted forging design for strength under heavy load
• Precision-machined crown with valve reliefs
• Anti-detonation groove to minimize knock risk
• Forced pin oiling for improved lubrication at wrist pin
• Pre-gapped plasma-moly ring set for good sealing and performance
• Designed for severe-duty performance applications

Specifications

• Bore Diameter: 84.00 mm
• Stroke: 85 mm
• Compression Height: 30.50 mm
• Dome Volume: ~7.00 cc
• Compression Ratio: ~10.0-10.3 :1
• Wrist Pin Diameter: 20 mm (0.787 in)
• Piston Material: 2618 forged aluminum
• Piston Weight: ~293 g
• Ring Set Part: 8400XX

Included Components

• 4x Forged pistons
• 4x Wrist pins (20 mm)
• 1x Pre-gapped ring set (plasma-moly)
• Piston locks / circlips

Product Description

The Wiseco K590M84 is a forged piston set engineered for Mazda's 1.8 L BP-series engines (Miata / MX-5 and Protege). With a bore of 84.00 mm and a compression height of 30.50 mm, these pistons are built to deliver a high-performance compression ratio of around 10.0-10.3:1 using their ~7 cc dome design. The pistons are forged from 2618 aluminum, offering both strength and lightweight characteristics.

The ArmorGlide® coating on the skirts reduces friction, improves reliability, and minimizes the risk of piston seizure under stress. The strutted forging and anti-detonation groove help the pistons handle high loads and resist knock, while forced pin oiling ensures proper lubrication of the wrist pins. This set is ideal for performance builders working on naturally aspirated or mildly tuned BP engines who want a durable, race-ready piston solution.

Installation is straightforward, with included 20 mm wrist pins and a pre-gapped plasma-moly ring set (8400XX). These forged pistons are a reliable upgrade over stock components, especially for those seeking long-term durability and better high-RPM performance.