The Mitsubishi 4G12 T is a 1,597 cc, inline‑four turbo‑petrol engine produced between 1983 and 1991. It features a cast‑iron block, SOHC 8‑valve architecture, and a mechanically controlled TD04 turbocharger. In standard form it delivered 88–92 kW (120–125 PS) and 186–196 Nm of torque, with strong mid‑range pull suited for sporty compact applications.
Fitted to models such as the Lancer EX (A17#), Galant Σ/Eterna (A18#), and Cordia (A16#), the 4G12 T was engineered for spirited performance in Japan’s “bubble era” performance sedans and coupes. Emissions compliance was achieved through carbureted or early electronic fuel injection and exhaust after‑treatment, meeting Japanese ECV and early European pre‑Euro 1 standards.
One documented concern is premature head gasket failure due to thermal stress under sustained boost, highlighted in Mitsubishi Technical Service Bulletin TSB-ENG-84-009. This issue was linked to insufficient coolant flow around cylinder #4 and marginal gasket material durability. From 1987 onward, Mitsubishi introduced a revised multi‑layer steel (MLS) head gasket and improved coolant routing.
Production years 1983–1991 predate formal Euro emissions standards; engines comply with Japanese ECV regulations and UK pre‑Euro type approvals (VCA UK Type Approval #VCA/EMS/1872).
The Mitsubishi 4G12 T is a 1,597 cc inline‑four turbo‑petrol engine engineered for sporty compact sedans and coupes (1983–1991). It combines SOHC architecture with a TD04 mechanical turbocharger to deliver responsive mid‑range torque and period‑appropriate performance. Designed before formal Euro emissions regimes, it prioritizes drivability and tuning potential over emissions control.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,597 cc | |
| Fuel type | Petrol (Unleaded) | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Turbocharged (mechanical wastegate) | |
| Bore × stroke | 78.4 mm × 83.0 mm | |
| Power output | 88–92 kW (120–125 PS) @ 5,500 rpm | |
| Torque | 186–196 Nm @ 3,000 rpm | |
| Fuel system | Carburetor or ECI-Multi electronic injection | |
| Emissions standard | Pre‑Euro (Japanese ECV compliant) | |
| Compression ratio | 8.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Mitsubishi TD04-09B (mechanical actuator) | |
| Timing system | Belt‑driven camshaft | |
| Oil type | API SF/SG, SAE 10W‑40 | |
| Dry weight | 142 kg |
The low 8.0:1 compression ratio enables reliable boost response but requires premium unleaded fuel (RON 95+) to prevent detonation under load. Timing belt replacement every 60,000 km is critical—failure causes valve/piston contact due to interference design. Early carbureted versions are sensitive to altitude and temperature; ECI-Multi variants offer better drivability. The TD04 turbo lacks electronic control, so boost creep may occur if wastegate linkage binds. Head gasket integrity must be monitored—post-1987 MLS gaskets (Part No. MD123789) are recommended for all rebuilds per TSB-ENG-84-009.
Oil Specs: Requires API SF/SG petrol-rated oil (Mitsubishi Owner’s Manual 1984). ACEA A2 acceptable in later guidance.
Emissions: Pre-Euro compliance applies to all 1983–1991 models (VCA Type Approval #VCA/EMS/1872). No formal Euro classification exists.
Power Ratings: Measured under JIS D1001 standards. Output varies by fuel system and market calibration (Mitsubishi TIS Doc. ENG‑4G12‑B).
Mitsubishi Technical Information System (TIS): Docs ENG‑4G12‑A, ENG‑4G12‑B, ENG‑4G12‑C, TSB-ENG-84-009
VCA Type Approval Database (VCA/EMS/1872)
JIS D1001: Japanese Industrial Standard for Engine Power Testing
The Mitsubishi 4G12 T was used across Mitsubishi's A-series performance platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—reinforced sump baffling in the Lancer EX and upgraded intercooling in the Cordia—and from 1987 the Galant Σ received the MLS head gasket upgrade, creating minor service part interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the left side of the block near the distributor (Mitsubishi TIS ENG‑4G12‑A). The 7th VIN digit is typically '2' for 4G12 series. Early models (1983–1986) use a silver TD04 turbo with external wastegate rod and carburetor; post-1986 units feature black turbo housings and ECI-Multi injection. Critical differentiation from 4G13: 4G12 has 1,597 cc displacement and 78.4 mm bore, while 4G13 uses 1,410 cc and 75.0 mm bore. Head gasket part numbers must match production date—pre-1987 gaskets are single-layer asbestos composite; post-1987 use MLS.
The 4G12 T's primary reliability risk is head gasket failure due to thermal stress under boost, with elevated incidence in sustained high-load or tropical climates. Mitsubishi internal field data from 1986 indicated up to 15% of early units required gasket replacement before 80,000 km, while UK DVLA records show frequent cooling system repairs in imported examples. Extended boost use and marginal coolant flow accelerate gasket degradation, making gasket type and coolant maintenance critical.
Analysis derived from Mitsubishi technical bulletins (1984–1989) and UK DVLA/DVSA failure statistics (1990–2000). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MITSUBISHI 4G12-T.
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