Nissan RD28 Specifications
| Engine Model: Nissan RD28 |
| Engine Type: 4-cycle inline 6-cylinder OHV 12-valve liquid-cooled diesel |
| Total Displacement: 172.5 cu.in (2.83 L) |
| Rated Engine Power: 90-100 Hp (67-74 kW) at 4800 rpm |
| Fuel System Type: Indirect fuel injection |
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The Nissan RD28 engine is a 2.8-liter,
inline-six, water-cooled, four-stroke diesel engine that served as one
of Nissan’s core diesel powerplants for heavy-duty passenger vehicles,
commercial fleets, and export-market sedans through the 1980s, 1990s,
and early 2000s. As the naturally aspirated base version of the
RD-series - comprising RD28, RD28T, and RD28Ti - the RD28 emphasizes
mechanical simplicity, long-term durability, smooth operation, and
tolerance for various fuel qualities.
Unlike its turbocharged counterparts, the RD28 is designed for moderate
power output but exceptional reliability under continuous-load
operation. It features a cast-iron block, cast-iron OHV cylinder head, a
gear-driven camshaft, indirect injection via pre-combustion chambers,
and a fully mechanical fuel system. These attributes allow the RD28 to
achieve remarkable longevity in fleet, taxi, and off-road environments
where low maintenance and high durability are required.
Though not a high-performance engine, the RD28 provides strong low-end
torque, smooth idle, and predictable power delivery. Its inline-six
layout contributes to low vibration and quiet running relative to
similarly sized four-cylinder diesels. The naturally aspirated RD28
remains popular in many markets for its ability to function reliably in
harsh climates, hot or cold, and under conditions of minimal
maintenance.
The RD28 engine displaces approx. 2,826 cc (172.5 cubic inches). Bore is
approx. 85.0 mm (3.35 in), and stroke is approx. 83.0 mm (3.27 in),
providing a nearly square geometry optimized for balanced torque and
smooth operation. Compression ratio is 21.0:1 - 22.0:1 depending on
version and emissions calibration. Power output for the naturally
aspirated RD28 is 90-100 hp at 4,800 rpm. Maximum torque is approx.
130-145 lb-ft (approx. 175-195 Nm) at approx. 2,400-2,800 rpm. Idle
speed is approx. 650-750 rpm. The firing order is 1-5-3-6-2-4.
The engine block is cast iron with deep skirts, ensuring structural
rigidity and resistance to cylinder distortion under high thermal and
mechanical loads. The crankshaft is forged steel and supported by seven
main bearings, offering smoothness and durability under prolonged
operation.
The connecting rods are forged steel with robust big-end bearings.
Pistons are cast aluminum alloy with heat-treated crowns and reinforced
ring lands. The bottom end is engineered for extended service life,
especially in fleet use.
The RD28 features a cast-iron OHV (overhead-valve) cylinder head.
Features include:
- Gear-driven camshaft
- Hardened pushrods
- Rocker arms with screw-and-locknut adjustment
- Two valves per cylinder
- Indirect-injection (IDI) pre-combustion chambers
- Glow plugs for cold starting
The gear-driven camshaft improves valvetrain reliability and eliminates
timing belts or chains. Valve lash must be adjusted periodically to
maintain proper operation. The IDI system enhances combustion stability,
reduces engine noise, and improves cold-start performance.
The RD28 uses a fully mechanical diesel fuel system, optimized for
reliability and fuel-quality tolerance.
Components include:
- Mechanical lift pump
- Water-separating sediment bowl
- Primary and secondary fuel filters
- Inline mechanical injection pump (Bosch-type)
- Multi-hole mechanical injectors
- High-pressure steel injector lines
- Fuel-return circuit
Injection timing is set by rotating the pump body. The mechanical
governor maintains stable rpm, idle quality, and throttle response. This
simple design contributes to the engine’s longevity, especially in
remote regions.
The lubrication system is a full-pressure wet-sump design.
Specifications:
- Oil capacity 5.0-6.0 liters (approx. 5.3-6.3 US qt)
- Oil pressure approx. 45-65 psi at 3,000 rpm; approx. 15-20 psi at idle
- Recommended oil grades: 15W-40 or 10W-30 diesel-rated oils (API CF-CI)
A crankshaft-driven trochoid oil pump provides stable lubrication. Oil
is routed to crankshaft bearings, connecting rods, camshaft bearings,
rocker arms, and cylinder walls. A spin-on full-flow oil filter ensures
clean operation.
The RD28 uses a forced-circulation liquid cooling system.
Specifications:
- Thermostat begins opening approx. 82°C (180°F)
- Fully open approx. 95°C (203°F)
- Cooling-system capacity 8.0-9.0 liters (approx. 8.4-9.5 US qt)
Components include:
- Belt-driven centrifugal water pump
- Radiator (copper-brass or aluminum)
- Coolant expansion tank
- Heater core
- Temperature sensors for instrumentation
The cooling system is critical for preventing overheating under
continuous-load conditions.
| Intake and Exhaust Systems |
The RD28 intake system includes:
- Heavy-duty air-cleaner housing
- Replaceable paper air filter
- Intake ducting
- Snorkel option on off-road variants
- Long-runner intake manifold
The system is designed to provide clean airflow in dusty or harsh
environments.
Exhaust system components include:
- Cast-iron exhaust manifold
- Exhaust piping
- Catalytic converter in some markets
- Muffler assembly
The exhaust system prioritizes durability, low backpressure, and low
noise.
The RD28 uses a 12-volt electrical system
including:
- Alternator (approx. 50-80 amps)
- Reduction-gear starter motor
- Glow plugs
- Glow-plug relay and control timer
- Heavy-duty battery (70-100 Ah)
Glow plugs are essential for reliable cold starts due to the IDI design.
- Length 770-820 mm (30.3-32.3 in)
- Width 620-660 mm (24.4-26.0 in)
- Height 690-760 mm (27.2-29.9 in)
Dry weight approx. 210-240 kg (463-529 lb) depending on accessories.
Recommended intervals:
- Oil and filter every 5,000-7,500 km (3,000-5,000 mi)
- Fuel filters every 10,000-20,000 km
- Air filter every 10,000-15,000 km
- Valve lash adjustment every 20,000-30,000 km
- Coolant replacement every 2 years
- Glow-plug testing every 20,000 km
Compression pressure:
- Approx. 360-420 psi
- Cylinder variation less than 10 percent
- Cylinder-head bolts: 110-130 Nm (81-96 lb-ft)
- Main-bearing caps: 110-130 Nm (81-96 lb-ft)
- Connecting-rod bolts: 70-80 Nm (52-59 lb-ft)
- Flywheel bolts: 130-150 Nm (96-111 lb-ft)
- Intake-manifold bolts: 20-25 Nm (15-18 lb-ft)
- Exhaust-manifold nuts: 30-35 Nm (22-26 lb-ft)
- Injector-clamp bolts: 25-30 Nm (18-22 lb-ft)
- Oil-drain plug: 30-35 Nm (22-26 lb-ft)
The RD28 engine appeared in:
- Nissan Laurel (C32, C33, C34)
- Nissan Cedric / Gloria diesel trims
- Nissan Patrol (limited non-turbo diesel markets)
- Nissan Crew (commercial/fleet)
- Taxis and government vehicles in export markets
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