The Mazda KJ-ZEM is a 2,255 cc, 60‑degree V6 petrol engine produced between 1995 and 2002. It features a cast iron block, aluminium heads, DOHC per bank, and sequential multi‑point fuel injection. Its defining technology is the Miller cycle, enabled by a Lysholm-type twin-screw supercharger, which optimises thermal efficiency for strong low-end torque and improved fuel economy.
Fitted primarily to the Mazda Millenia (Eunos 800 in Japan) luxury sedan, the KJ-ZEM was engineered for refined, effortless performance with an emphasis on smooth power delivery and quiet operation. Emissions compliance for its era was managed through its advanced electronic fuel injection and exhaust after-treatment, meeting Japanese and international standards (including ULEV in North America) prevalent during its production run.
One documented engineering challenge involves the complex supercharger system, which requires precise maintenance. Service documentation notes potential for supercharger rotor seal wear or coolant leaks in the intercooler circuit over extended periods. Mazda provided specific service procedures to address these concerns, as outlined in Technical Service Bulletin 01-005/98.
Mazda
Production years 1995–2002 meet applicable ULEV and Japanese emissions standards for their respective markets during that period (Mazda Service Manual, Group 2K; California Air Resources Board Executive Order D-344).
The Mazda KJ-ZEM is a 2,255 cc 60-degree V6 Miller-cycle petrol engine engineered for premium sedans (1995-2002). It combines a twin-screw supercharger with variable intake valve timing to deliver exceptional low-rpm torque and smooth, linear power. Designed to meet stringent ULEV standards, it prioritises efficiency and refinement without sacrificing performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,255 cc | |
| Fuel type | Petrol | |
| Configuration | 60° V6, DOHC, 24-valve | |
| Aspiration | Supercharged (Lysholm twin-screw) | |
| Bore × stroke | 78.0 mm × 78.4 mm | |
| Power output | 156–166 kW (210–220 PS) | |
| Torque | 294–300 Nm @ 3,500 rpm | |
| Fuel system | Sequential multi-point fuel injection (SFI) | |
| Emissions standard | ULEV (US), Japanese 1998 regulations | |
| Compression ratio | 8.5:1 (effective); 10.0:1 (geometric) | |
| Cooling system | Water-cooled (separate supercharger intercooler circuit) | |
| Turbocharger | None | |
| Timing system | Chain-driven | |
| Oil type | SAE 5W-30 (API SJ/SL or equivalent) | |
| Dry weight | 195 kg |
The Miller-cycle and supercharger provide exceptional low-RPM torque for relaxed driving but demand strict adherence to maintenance schedules for the supercharger and its dedicated coolant system. Using the specified 5W-30 oil is critical for engine and supercharger longevity. The timing chain is generally robust but should be inspected for wear during major services. The complex intake system requires periodic inspection for vacuum leaks. Supercharger rotor seals are a known wear item and should be checked if boost pressure drops or oil consumption increases.
Oil Specs: Requires SAE 5W-30 with API SJ/SL rating or equivalent specification (Mazda Workshop Manual, Millenia).
Emissions: Certified as ULEV by California ARB (Executive Order D-344) and meets Japanese 1998 emissions regulations (MLIT).
Power Ratings: Measured under SAE J1349 standards. Output figures are for supercharged variants (Mazda PT-1998).
Mazda Workshop Manual, Millenia (Model Year 1995)
Mazda PT-1998 Specifications Document
Mazda Technical Service Bulletin 01-005/98 (Supercharger Service)
California Air Resources Board Executive Order D-344
Japanese Ministry of Land, Infrastructure, Transport and Tourism (MLIT) - 1998 Emissions Regulations
The Mazda KJ-ZEM was used exclusively in Mazda's Millenia platform with longitudinal mounting. This engine received minor ECU and accessory drive adaptations for different model years and markets (notably North America and Japan), creating potential interchange limits for ancillary components. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front face of the cylinder block, near the timing cover (Mazda Workshop Manual, Millenia). The 8th digit of the VIN typically corresponds to the engine type for this era. The KJ-ZEM is visually identified by its 60-degree V6 configuration, prominent Lysholm supercharger mounted atop the intake manifold, and "KJ-ZEM" casting marks on the block. Critical differentiation from the naturally aspirated KL engine: The KJ-ZEM has a supercharger and associated intercooler plumbing, while the KL does not. When sourcing parts, verify the specific model year and market, as ECU calibrations and emissions equipment can vary.
The KJ-ZEM's primary reliability risk is age-related wear in the supercharger system, with elevated incidence in high-mileage or poorly maintained examples. Mazda service documentation highlights supercharger rotor seal failure and intercooler coolant leaks as common causes for drivability complaints. Extended service intervals and use of incorrect oil can accelerate wear on internal engine components, making adherence to the factory maintenance schedule critical.
Analysis derived from Mazda technical bulletins (1995-2002) and workshop manual procedures. Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MAZDA KJ-ZEM.
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