Nissan TD25 Specifications
| Engine Model: Nissan TD25 |
| Engine Type: 4-cycle inline 4-cylinder OHV 8-valve liquid-cooled diesel |
| Total Displacement: 152.2 cu.in (2.49 L) |
| Rated Engine Power: 81 Hp (60 kW) at 4300 rpm |
| Fuel System Type: Indirect injection |
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The Nissan TD25 is a 2.5-liter, naturally aspirated
inline four-cylinder diesel engine that represents the culmination of Nissan’s
TD series development, serving as an enlarged version of the TD23 while sharing
the same heavy-duty architecture. Produced throughout the late 1980s and into
the early 2000s, this engine was engineered for commercial applications where
reliability, durability, and serviceability in challenging operating conditions
were paramount.
The TD25 features a cast iron cylinder block and cylinder head, an overhead
valve (OHV) valvetrain with eight valves, and an indirect injection fuel system
- a configuration that prioritizes mechanical simplicity and longevity over
power output. The engine’s most notable characteristic is its gear-driven timing
system, which eliminates the timing belts or chains found on contemporary
engines, providing exceptional reliability in commercial service where
maintenance intervals may be extended or where operating environments are harsh.
The TD25 is a strictly mechanical engine with no electronic controls, relying on
a mechanical injection pump and simple electrical system. This absence of
complex electronics makes the engine highly valued in markets with limited
maintenance infrastructure, where vehicles often operate in remote locations or
where diagnostic equipment is unavailable. The engine found widespread
application in Nissan commercial vehicles, including the Datsun Truck and Navara
pickups, Atlas and Cabstar light trucks, and Caravan and Urvan vans,
establishing itself as a dependable workhorse in Nissan’s commercial vehicle
lineup.
The TD25 is a four-stroke, water-cooled diesel engine operating on the
compression-ignition principle. The engine architecture is an inline
four-cylinder configuration with a total displacement of 2,494 cc (152.2 cu.in),
derived from a bore of 92.9 mm (3.66 in) and a stroke of 92.0 mm (3.62 in). This
nearly square bore-to-stroke ratio provides a balanced combination of torque
production and engine responsiveness. The compression ratio is set at 22.2:1, a
relatively high value characteristic of indirect injection diesel engines,
ensuring reliable cold-start performance and efficient combustion.
The valvetrain utilizes an overhead valve (OHV) configuration with a camshaft
located in the cylinder block. The camshaft is driven directly by the crankshaft
through a gear train, a system that eliminates timing belts or chains and
provides precise valve timing without the need for tensioners or periodic
replacement. Each cylinder utilizes two valves - one intake and one exhaust -
actuated via pushrods and rocker arms.
Valve clearances require periodic mechanical adjustment using an adjusting screw
on the rocker arm. The firing order for this inline four-cylinder engine is
1-3-4-2, ensuring even firing intervals of 180 degrees of crankshaft rotation.
The redline is set at 4,500 rpm, with maximum power and torque peaks occurring
at lower engine speeds to preserve longevity in commercial applications.
Performance outputs reflect the engine’s focus on durability rather than power.
Maximum power is rated at 60 kW (81 hp) at 4,300 rpm. Maximum torque is rated at
160 Nm (118 lb-ft) at 2,200 rpm, a low engine speed that provides strong pulling
power for laden vehicles in urban and off-road conditions. The idle speed is set
at 650 rpm to 700 rpm when the engine is at operating temperature.
The cylinder block is manufactured from cast iron, a
material chosen for its exceptional rigidity, wear resistance, and durability
under the high compression pressures characteristic of diesel operation. The
block features a deep-skirt design that extends below the crankshaft centerline,
providing structural stiffness essential for commercial vehicle applications
where sustained high loads are common.
The cylinder bores are cast directly into the block and are finished with a
plateau honing process that optimizes oil retention and piston ring sealing. The
block incorporates replaceable dry-type cylinder liners in certain variants,
allowing for overhaul and bore restoration without replacing the entire block.
The crankcase is reinforced with heavy webbing between cylinder bores to
minimize distortion under thermal and mechanical stress.
The main bearing caps are manufactured from nodular cast iron and are secured
with two bolts per cap, with the center main bearing featuring four bolts on
certain variants for additional strength. The cylinder block incorporates the
gear train housing at the front, which houses the crankshaft timing gear,
camshaft drive gear, and injection pump drive gear. The block includes
provisions for the mechanical fuel injection pump mounting, oil filter mounting,
and engine mounting points specific to each vehicle application.
The cylinder head is manufactured from cast iron,
matching the cylinder block material to ensure uniform thermal expansion and
sealing integrity. The head features an overhead valve (OHV) configuration with
the camshaft housed in the cylinder block. The combustion chambers are of the
indirect injection (IDI) design, incorporating pre-combustion chambers or swirl
chambers that promote thorough mixing of fuel and air before ignition.
Each cylinder utilizes two valves - one intake and one exhaust - arranged in a
cross-flow configuration that separates the intake and exhaust passages. The
valves are actuated by rocker arms mounted on a rocker shaft, with pushrods
transmitting motion from the camshaft to the rocker arms. Valve clearances
require periodic adjustment using an adjusting screw and locknut on the rocker
arm.
The intake valves have a diameter of 38.0 mm (1.50 in), while the exhaust valves
have a diameter of 34.0 mm (1.34 in). The exhaust valves are equipped with
hardened tips and chrome-plated stems for wear resistance. The valve seat
inserts are manufactured from high-cobalt or nickel-based alloys to withstand
the thermal and mechanical stresses of diesel operation. The cylinder head
gasket is a composite or multi-layer steel (MLS) design, providing robust
sealing under the high cylinder pressures generated by the compression ignition
process.
The TD25 is equipped with a mechanical indirect
injection (IDI) fuel system. A mechanical in-line injection pump, mounted on the
side of the cylinder block and driven by the front gear train, pressurizes fuel
and delivers it to injection lines leading to each cylinder. The injection pump
is a Bosch or Zexel design depending on production date, featuring a mechanical
governor that controls fuel delivery based on engine speed and accelerator pedal
position. The pump includes a manual cold-start advance mechanism that adjusts
injection timing for improved cold-start performance.
The injection lines are high-pressure steel tubes routed individually from the
injection pump to the injectors mounted in the cylinder head. The injectors are
of the nozzle-and-holder type, incorporating a spring-loaded pintle nozzle that
opens at a predetermined pressure, atomizing the fuel into the pre-combustion
chamber. The injection pressure is 12.0 MPa (1,740 psi) to 13.0 MPa (1,885 psi)
depending on engine speed and load. The fuel filtration system includes a
primary water separator and a secondary replaceable fuel filter to protect the
injection pump and injectors from contamination. A manual primer pump is
incorporated into the fuel system to facilitate bleeding of air after filter
replacement or fuel system service.
The lubrication system is a forced-feed, full-flow
filtration design utilizing a gear-type oil pump mounted at the front of the
engine and driven by the crankshaft through the gear train. The oil pump draws
lubricant from the sump through a strainer and delivers it to the main oil
gallery. The system maintains stable oil pressure across the operating range,
with a pressure relief valve calibrated to open at approximately 3.5 bar (51
psi) to 4.0 bar (58 psi).
An oil cooler is not fitted in standard applications, though the engine design
accommodates one for certain heavy-duty vehicle configurations. The engine
employs a full-flow spin-on oil filter mounted on the cylinder block. The oil
pan is constructed from stamped steel and has a capacity of 5.5 liters (5.8 US
qt) to 6.0 liters (6.3 US qt) depending on the variant and vehicle application.
The engine requires 10W-30, 15W-40, or 20W-50 diesel engine oil meeting API CD
or higher specification.
The cooling system is a pressurized, water-cooled
design utilizing a centrifugal water pump driven by the accessory drive belt.
The system maintains engine operating temperature within a range of 80°C to 90°C
(176°F to 194°F) under normal conditions. The coolant circuit includes a
thermostatic bypass that facilitates rapid warm-up and reduces internal friction
during cold starts. The water pump is mounted on the front of the engine block
and is driven by the same belt that drives the alternator.
The cast iron cylinder block and cylinder head provide robust thermal mass,
contributing to stable operating temperatures under varying loads. A cross-flow
radiator with a mechanical or electric cooling fan supplements the system at low
vehicle speeds and during idle conditions. The total coolant capacity for the
engine and cooling system is 7.0 liters (7.4 US qt) to 8.0 liters (8.5 US qt)
depending on the vehicle application.
| Intake and Exhaust Systems |
Intake System: The intake system incorporates a cast
iron intake manifold designed for durability. Air is drawn through a heavy-duty
paper element air cleaner before entering the intake manifold. The engine does
not utilize turbocharging or intercooling in its standard naturally aspirated
configuration.
Exhaust System: The exhaust system incorporates a cast iron exhaust manifold
merging into a single exhaust pipe. The system includes a muffler but does not
utilize catalytic converters on the majority of applications, reflecting the
engine’s design for markets with less stringent emissions regulations.
Engine Management: The TD25 utilizes no electronic
engine management system. Fuel delivery is controlled mechanically by the
injection pump governor. The electrical system consists of a starter motor, glow
plugs for cold-start assistance, and basic sensors for the instrument cluster
including oil pressure, coolant temperature, and charge warning lights.
Glow Plug System: The engine is equipped with glow plugs installed in each
cylinder head to assist with cold starting. The glow plugs are energized through
a glow controller that activates them for a predetermined duration based on
coolant temperature. The glow plug system includes a dash-mounted indicator
light that extinguishes when the plugs have reached operating temperature.
The engine length, measured from the front gear cover
to the flywheel housing face, is 750 mm (29.5 in). The width, measured at the
widest point including the injection pump and exhaust manifold, is 650 mm (25.6
in). The height, measured from the oil pan bottom to the top of the cylinder
head cover, is 800 mm (31.5 in).
The dry weight (without fluids, starter, alternator, or clutch or transmission)
is 250 kg (551 lb). The fully dressed weight for a vehicle application,
including the alternator, starter, injection pump, and fluids, is 285 kg (628
lb).
The service life of the TD25 under proper operating
conditions is engineered to exceed 400,000 km (250,000 mi) in commercial
applications, with many units reaching 500,000 km (310,000 mi) before major
overhaul. Oil change intervals are recommended at 5,000 km (3,100 mi) for severe
service conditions or 7,500 km (4,700 mi) under normal operating conditions. The
engine requires diesel engine oil meeting API CD or higher specification in
viscosities of 10W-30, 15W-40, or 20W-50.
Valve clearance inspection and adjustment is mandated every 20,000 km (12,400
mi). The intake valve clearance is set at 0.30 mm (0.012 in) cold, while the
exhaust valve clearance is set at 0.35 mm (0.014 in) cold. Replacement of the
fuel filter is required every 10,000 km (6,200 mi) or 12 months.
The air cleaner element requires replacement every 10,000 km (6,200 mi), with
more frequent servicing in dusty environments. The coolant must be replaced
every 2 years or 40,000 km (25,000 mi), using a nitrite-free, long-life coolant
formulation. The accessory drive belt requires inspection at each service
interval, with replacement recommended every 40,000 km (25,000 mi) or sooner if
cracking or wear is evident.
The cylinder head bolts follow a multi-stage torque
procedure. The M12 cylinder head bolts receive an initial torque of 50 Nm (37
lb-ft), followed by a 60-degree angle, and a final 60-degree angle in a
specified sequence. The main bearing cap bolts are torqued to 80 Nm (59 lb-ft).
The connecting rod bolts are tightened to 45 Nm (33 lb-ft). The
flywheel-to-crankshaft bolts receive a torque of 100 Nm (74 lb-ft).
The rocker arm shaft pedestal bolts are torqued to 25 Nm (18 lb-ft). The
injection pump drive gear bolt is torqued to 80 Nm (59 lb-ft). The injector
hold-down nuts are torqued to 30 Nm (22 lb-ft). The intake manifold bolts are
torqued to 20 Nm (15 lb-ft). The exhaust manifold bolts are torqued to 25 Nm (18
lb-ft). The glow plugs are torqued to 15 Nm (11 lb-ft).
The TD25 was utilized across a broad range of Nissan
commercial vehicles throughout the late 1980s, 1990s, and early 2000s. In the
light truck segment, the engine powered the Nissan Datsun Truck and Navara
pickups (D21 and D22 generations, produced from 1988 to 2001), where its
durability and mechanical simplicity made it suitable for agricultural,
construction, and utility applications. The engine was also installed in the
Nissan Atlas (F23 generation, produced from 1995 to 2007) and the Nissan Cabstar
(F22 and F23 generations, produced from 1988 to 2007), serving in flatbed, box
truck, and chassis cab configurations for urban delivery and light commercial
transport.
In the van and passenger transport segment, the TD25 powered the Nissan Caravan
and Urvan (E24 generation, produced from 1988 to 1996) and the Nissan Homy (E24
generation, produced from 1988 to 1996), where the engine’s torque
characteristics and reliability were valued for passenger transport, ambulance,
and cargo van applications.
The TD25 was gradually phased out in the early 2000s as Nissan introduced the
more modern QD and ZD diesel engine families featuring direct injection and
turbocharging. However, the TD25 remains in service in substantial numbers
across markets in Southeast Asia, the Middle East, Africa, and South America,
where its mechanical simplicity and robust construction continue to be valued in
regions with limited access to specialized diagnostic equipment and advanced
maintenance facilities.
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