The Mitsubishi 4D55 T is a 2,378 cc, inline‑four turbo‑diesel engine produced between 1983 and 1995. It features a cast‑iron block, SOHC 8‑valve architecture, and a mechanically controlled K24 turbocharger. In standard form it delivered 63–70 kW (86–95 PS) and 192–235 Nm of torque, with robust low‑end pull suited for utility and off‑road applications.
Fitted to models such as the Pajero (L04#), Delica (L300), and L200/Triton (K7#), the 4D55 T was engineered for durability in commercial and rugged environments. Emissions compliance was achieved through indirect injection and exhaust after‑treatment, meeting Japanese and early European standards (pre‑Euro 1) during its production run.
One documented concern is premature turbocharger bearing failure due to oil coking under sustained high load or infrequent oil changes. This issue was noted in Mitsubishi Technical Service Bulletin TSB-ENG-85-007, which recommended revised oil feed restrictors and improved oil return lines to mitigate heat soak damage.
Production years 1983–1995 predate formal Euro emissions standards; engines comply with Japanese ECV regulations and UK pre‑Euro type approvals (VCA UK Type Approval #VCA/EMS/2103).
The Mitsubishi 4D55 T is a 2,378 cc inline‑four turbo‑diesel engineered for light commercial and off‑road vehicles (1983–1995). It combines indirect injection with a K24 mechanical turbocharger to deliver high low‑rpm torque and field reliability. Designed before formal Euro emissions regimes, it prioritizes mechanical simplicity and serviceability over emissions control.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,378 cc | |
| Fuel type | Diesel | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Turbocharged (mechanical wastegate) | |
| Bore × stroke | 91.1 mm × 91.1 mm | |
| Power output | 63–70 kW (86–95 PS) @ 4,200 rpm | |
| Torque | 192–235 Nm @ 2,000–2,500 rpm | |
| Fuel system | Indirect injection (Bosch VE rotary pump) | |
| Emissions standard | Pre‑Euro (Japanese ECV compliant) | |
| Compression ratio | 21.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Mitsubishi TD04-13G/K24 (mechanical actuator) | |
| Timing system | Gear‑driven camshaft (maintenance‑free) | |
| Oil type | API CC/CD, SAE 10W‑30 or 15W‑40 | |
| Dry weight | 225 kg |
The indirect injection and gear-driven camshaft provide rugged reliability but limit refinement and emissions performance. Oil changes every 5,000–7,500 km with API CC/CD diesel-rated oil are essential to prevent turbo bearing coking and injector pump wear. Use of ultra-low-sulfur diesel (ULSD) is not required but improves combustion cleanliness. The mechanical K24 turbo lacks electronic boost control, so boost creep or lag may occur if wastegate linkage binds. Turbo oil feed/return lines must be inspected regularly—collapsed or carbon-restricted lines accelerate bearing failure per TSB-ENG-85-007.
Oil Specs: Requires API CC/CD diesel-rated oil (Mitsubishi Owner’s Manual 1985). ACEA B2 acceptable in later service guidance.
Emissions: Pre-Euro compliance applies to all 1983–1995 models (VCA Type Approval #VCA/EMS/2103). No formal Euro classification exists.
Power Ratings: Measured under JIS D1001 standards. Output varies by market calibration and turbo variant (Mitsubishi TIS Doc. ENG‑4D55‑B).
Mitsubishi Technical Information System (TIS): Docs ENG‑4D55‑A, ENG‑4D55‑B, ENG‑4D55‑C, TSB-ENG-85-007
VCA Type Approval Database (VCA/EMS/2103)
JIS D1001: Japanese Industrial Standard for Engine Power Testing
The Mitsubishi 4D55 T was used across Mitsubishi's L-series utility platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—reinforced sump in the Pajero and upgraded cooling in the L200—and from 1989 the Delica received a revised turbo actuator, creating minor ECU (mechanical governor) interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the left side of the block near the injection pump (Mitsubishi TIS ENG‑4D55‑A). The 7th VIN digit is typically '5' for 4D55 series. Early models (1983–1988) use a silver K24 turbo with external wastegate rod; post-1989 units feature black turbo housings with integrated actuator. Critical differentiation from 4D56: 4D55 has 2,378 cc displacement and 91.1 mm bore, while 4D56 uses 2,477 cc and 92.0 mm bore. Injection pump calibration tags must match model year—Delica pumps differ from Pajero due to governor spring rates.
The 4D55 T's primary reliability risk is turbocharger bearing failure due to oil coking, with elevated incidence in sustained high-load or desert use. Mitsubishi internal field reports from 1987 indicated up to 18% of early units required turbo replacement before 100,000 km, while UK DVLA records show frequent injector pump recalibrations in high-mileage examples. Extended idling and infrequent oil changes accelerate carbon buildup in oil galleries, making oil quality and interval adherence critical.
Analysis derived from Mitsubishi technical bulletins (1985–1992) and UK DVLA/DVSA failure statistics (1990–2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MITSUBISHI 4D55-T.
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