Mitsubishi Cylinder Head

1. The Modern Global 4B & 4J Passenger Group (1.8L – 2.4L DOHC)

These aluminum cylinder heads utilize chain-driven dual overhead camshafts (DOHC) and the Mitsubishi Innovative Valve timing Electronic Control (MIVEC) system.

• 4B11 (2.0L) & 4B12 (2.4L) Heads:
  • Applicable Models: ASX, Outlander / Airtrek, Galant Fortis.

• Technical Specifications: Design elements include high-flow symmetrical intake ports and extended spark plug apertures. The valvetrain employs direct-acting cam-on-bucket lifters.

• Variant Compatibility: The 4B11T turbocharged variant (found in Lancer Ralliart or ASX turbo models) incorporates structural reinforcement within the exhaust port architecture to accommodate increased thermal loads; this component is not compatible with naturally aspirated cylinder heads.

• 4J10 / 4J11 / 4J12 Heads (SOHC MIVEC Alternative):
  • Applicable Models: Late-iteration ASX and Outlander configurations.

• Technical Specifications: For specific efficiency-focused models, Mitsubishi transitioned to a single overhead cam (SOHC) configuration. This system facilitates dynamic variation of valve lift, duration, and timing via a integrated single-shaft rocker assembly.

2. The Heavy-Duty 4×4 Diesel Group (4M & 4N Families)

Designed for commercial and heavy-duty utility applications, these cylinder heads are engineered to maintain structural integrity under high compression ratios and sustained boost pressure.

• 4N15 / 4N16 Clean Diesel Heads (2.4L DOHC):
  • Applicable Models: Montero Sport, current Pajero Sport specifications.
  • Technical Specifications: An all-aluminum DOHC diesel architecture featuring integrated common-rail vertical injector sleeves and intake-side MIVEC implementation.
• 4M41 Turbo Diesel Heads (3.2L DOHC):
  • Applicable Models: Pajero.
  • Technical Specifications: A high-mass, 16-valve DOHC structure. These heads utilize specialized swirl-induction intake ports to optimize air-fuel homogenization at low engine speeds. Failure of the thermal management system under high-load conditions may result in inter-valve seat stress fractures.

3. The 3-Cylinder & Compact Small-Displacement Fleet

Engineered for compact vehicle platforms to optimize space utilization and total assembly mass.

• 3A92 / 3B21 Heads (1.0L – 1.2L Inline-3 DOHC):
  • Applicable Models: Mirage, eK / eK Wagon.
  • Technical Specifications: Lightweight three-cylinder aluminum design featuring a low-friction timing chain drive and integrated mounting points for component consolidation.

4. The Legacy Turbo & MZR Interchanges

• Evolution:
  • Architectural Classification: Models within the Evolution I-IX series utilize the cast-iron block 4G63T DOHC cylinder head (belt-driven, high-volume ports, external intake runners). Conversely, the Evolution X requires the aluminum 4B11T DOHC head (chain-driven). These assemblies represent distinct engineering generations and are not interchangeable.

• Colt & Eclipse:
  • Configuration Matrices: The Colt primarily utilizes the 4A91 (1.5L) aluminum series. The Eclipse architecture varies by production era: earlier iterations utilize the 4G63 / 4G64 series, while contemporary Eclipse Cross models employ the 4B40 (1.5L Direct Injection Turbo) platform.

Technical Considerations:

• Outlander / Airtrek Identification: Identification of Outlander heads requires visual verification of the drive system. Early iterations badged as “Airtrek” or “Outlander” utilize the 4G63/4G64 belt-driven architecture. Subsequent models utilize the 4B12 chain-driven architecture. These systems possess no component commonality.

• Montero Sport Diesel Specification: Verification of the engine code is mandatory: 4D56 (2.5L) versus 4N15 (2.4L). The 4D56 employs a timing belt and flush combustion surfaces. The aluminum 4N15 is chain-driven and features integrated combustion bowls for direct-injection piston compatibility. Incorrect assembly selection will lead to catastrophic mechanical interference during operation.