Isuzu 4HK1-TCN Specifications
| Engine Model: Isuzu 4HK1-TCN |
| Engine Type: 4-stroke in-line 4-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 316.9 cu.in (5.19 L) |
| Rated Engine Power: 150-155 Hp (110-114 kW) at 2600 rpm |
| Fuel System Type: Direct injection |
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The Isuzu 4HK1-TCN is a 5.2-liter,
four-cylinder, turbocharged diesel engine from Isuzu's modern "HK"
series. Introduced in the 2005 model year as a replacement for the
4HE1-TC engine, the 4HK1 family was developed to meet advanced exhaust
emission standards, specifically Euro III and Euro IV. The "TCN"
designation refers to a specific power rating calibrated for medium-duty
trucks, including the Isuzu NPR, NQR, and ELF (N-Series) models, as well
as various industrial equipment applications.
The 4HK1-TCN incorporates several significant technological advancements
over its predecessor. The engine features a single overhead camshaft
(OHC) operating four valves per cylinder, a high-pressure common rail
fuel injection system manufactured by Denso, a variable geometry system
(VGS) turbocharger with an intercooler, and a water-cooled exhaust gas
recirculation (EGR) system with an electronically controlled EGR valve.
These features result in increased maximum output and torque, improved
fuel efficiency, and reduced emissions compared to the older 4H series.
The engine produces 150-155 hp (110-114 kW) at 2,600 rpm and 404-419 Nm
(296-309 lb-ft) of torque available from 1,500 to 2,600 rpm. The
4HK1-TCN is recognized for its high torque at low speeds, making it well
suited for stop-start urban driving, longer highway trips, and demanding
industrial operations.
Engine Type: 4-stroke, water-cooled, inline-4, OHC diesel.
Displacement: 5,193 cc (316.9 cu.in), 5.2 L.
Bore x Stroke: 115.0 mm x 125.0 mm (4.53 in x 4.92 in).
Compression Ratio: 17.5:1.
Firing Order: 1-3-4-2.
Max Power (4HK1-TCN): 150-155 hp (110-114 kW) at 2,600 rpm.
Max Torque (4HK1-TCN): 404-419 Nm (296-309 lb-ft) at 1,500-2,600 rpm.
Aspiration: Turbocharged with intercooler and Variable Geometry System.
Combustion System: Direct injection.
Fuel System: High-pressure common rail.
Valvetrain: Single overhead camshaft, 4 valves per cylinder.
Camshaft Drive: Rear-mounted gear train for reduced noise.
Emissions Standard: Euro III or Euro IV.
Electrical System: 24V.
The cylinder block is constructed from high-strength cast iron, a
material chosen for its rigidity, thermal stability, and resistance to
distortion under the high cylinder pressures generated by the common
rail fuel system and turbocharger. The block features a deep-skirt
design providing excellent support for the crankshaft and main bearings.
Five main bearings support the crankshaft to ensure stability across the
engine's broad torque band from 1,500 rpm to 2,600 rpm.
The 4HK1-TCN uses high-durability dry-type cylinder liners pressed into
the block. Unlike wet liners, the dry liner design maintains a direct
metal-to-metal contact between the liner and the block casting, which
provides a rigid structure and efficient heat transfer. The cylinder
bores are finished with a precise honing pattern to promote oil
retention and piston ring sealing.
The block incorporates a full-length water jacket surrounding each
cylinder to maintain uniform operating temperatures under high-load
conditions. Integrated oil galleries are cast into the block to supply
pressurized oil to the main bearings, connecting rod bearings, and the
overhead camshaft. The engine features a rear gear train configuration,
with the camshaft and fuel injection pump driven by gears mounted at the
flywheel end of the block. This design reduces noise compared to
front-mounted chain or belt drives.
The cylinder head is manufactured from cast aluminum alloy and features
a cross-flow design. The intake manifold is positioned on one side of
the head, while the exhaust manifold with integrated EGR cooler is
positioned on the opposite side. This arrangement separates the hot
exhaust gases from the cooler intake charge, improving volumetric
efficiency.
The valvetrain uses a single overhead camshaft (OHC) that operates four
valves per cylinder (two intake, two exhaust) via roller rocker arms.
The four-valve configuration maximizes airflow into and out of the
combustion chamber, improving breathing efficiency and allowing the
engine to produce its peak torque across a wide rpm band from 1,500 to
2,600 rpm. The combustion chamber is a direct injection re-entrant type,
optimized for the common rail fuel system's injection characteristics.
The valve seats are manufactured from heat-resistant alloys to withstand
the high temperatures of turbocharged diesel combustion. The valve stem
seals are constructed from fluoroelastomer material to prevent oil
consumption. The engine requires periodic manual valve clearance
adjustment. The cold valve clearance specification for both intake and
exhaust valves is 0.40 mm (0.016 in). The adjustment procedure uses a
bridge and rocker arm mechanism. The adjusting screw lock nut tightening
torque is 22 Nm (16 lb-ft).
The fuel system on the 4HK1-TCN is a high-pressure common rail (HPCR)
system manufactured by Denso. The system consists of a supply pump
(Denso HP3), a common rail accumulator, and electronically controlled
injectors (Denso G2) with seven injection holes of 0.16 mm diameter
each. The supply pump pressurizes fuel to extremely high levels, storing
it in the common rail where it is available to all four injectors
simultaneously.
The engine control unit (ECU) governs injection timing, rail pressure,
and injection duration based on sensor inputs including crankshaft
position, camshaft position, coolant temperature, intake air
temperature, boost pressure, and accelerator pedal position. The HPCR
system enables multiple injection events per combustion cycle.
This strategy includes pilot injection to reduce combustion noise and
improve cold-start performance and main injection for power delivery. A
cartridge-type fuel filter with an integrated water separator protects
the high-pressure pump and injectors from contaminants and moisture. The
fuel system contributes significantly to the engine's compliance with
Euro III and Euro IV emission standards.
The lubrication system is a fully pressurized, wet-sump design using a
full-flow pressure circulation method. A gear-type oil pump, driven
directly from the crankshaft, draws oil from the oil pan through a
screened pickup tube. The oil is forced through a full-flow spin-on oil
filter before distribution to the main galleries. From the main
galleries, oil is supplied to the five main bearings, four connecting
rod bearings, camshaft bearings, turbocharger bearings, and the valve
train components.
The total oil system capacity is 20.5 L (21.7 qt). This substantial
capacity supports extended service intervals in medium-duty truck
applications by diluting contaminants and maintaining oil viscosity over
longer periods. An oil cooler, integrated with the engine cooling
system, maintains oil temperature within operational limits under
high-load conditions. The oil pressure relief valve prevents
over-pressurization at high engine speeds. A dipstick provides a
convenient method for checking oil level.
The cooling system is a pressurized, water-circulation design with a
cross-flow radiator. A centrifugal water pump with a cast impeller
circulates coolant through the engine block and cylinder head. Coolant
flows from the water pump into the cylinder block water jacket,
surrounding the cylinder liners to extract heat from the combustion
chamber lower regions, then moves upward into the cylinder head to cool
the valve seats, injectors, and combustion chambers before exiting
through the thermostat housing.
A wax pellet-type thermostat regulates coolant flow to maintain the
engine at operating temperature. The thermostat begins to open at 82-85
°C (180-185 °F). The engine block coolant capacity is 14.0 L (14.8 qt).
The total system capacity including the radiator and hoses is larger
depending on the specific vehicle installation. An engine-driven fan
draws air through the radiator core to dissipate heat.
The cooling system also serves the water-cooled EGR cooler, which
reduces the temperature of recirculated exhaust gases before they enter
the intake manifold. The system requires a high-quality Organic Acid
Technology (OAT) antifreeze to prevent corrosion and cavitation.
Electrical System (ECU): The engine control unit monitors crankshaft
position, camshaft position, coolant temperature, intake air
temperature, boost pressure, rail pressure, and battery voltage. The ECU
controls the fuel injectors, rail pressure regulator, EGR valve
position, glow plug operation, and diagnostic systems. For vehicle
applications, the ECU maintains governed engine speed regardless of load
within the engine's capacity.
Exhaust and Emissions System: The exhaust system includes the VGS
turbocharger, a water-cooled EGR system with an electronically
controlled EGR valve. The EGR system recirculates a portion of exhaust
gases back to the intake manifold to reduce combustion temperatures and
lower NOx emissions. The engine achieves Euro III or Euro IV compliance
without requiring a diesel particulate filter (DPF) or selective
catalytic reduction (SCR) system in most configurations.
Engine Mass (Dry): 530 kg (1,168 lb).
Overall Length: 1,033 mm (40.7 in).
Overall Width: 929 mm (36.6 in).
Overall Height: 1,040 mm (40.9 in).
Engine Oil Capacity: 20.5 L (21.7 qt) total system capacity.
Coolant Capacity (Block Only): 14.0 L (14.8 qt).
Coolant Type: OAT (Organic Acid Technology) antifreeze.
Fuel System: Denso high-pressure common rail.
Fuel Filter: Cartridge type with water separator.
Valve Clearance (Cold, Intake): 0.40 mm (0.016 in).
Valve Clearance (Cold, Exhaust): 0.40 mm (0.016 in).
Idle Speed: 650 ± 25 rpm.
Intake Valve Opens: 19° BTDC.
Intake Valve Closes: 53° ABDC.
Exhaust Valve Opens: 48° BBDC.
Exhaust Valve Closes: 14° ATDC.
The Isuzu 4HK1-TCN engine is used across a range of medium-duty trucks
and industrial equipment, primarily in Asia-Pacific, Latin American, and
other global markets.
Isuzu N-Series (Elf) Trucks:
Isuzu NPR 45-155 (Australia, 2022 model year, 114 kW/419 Nm).
Isuzu NPR75, NQR75, and NPS75 models (various global markets).
Isuzu ELF NMR 71 (Indonesia, 150 PS at 2,600 rpm, 404 Nm torque).
Isuzu NPS 4x4 light-duty truck (Philippines Army).
Industrial and Stationary Applications:
Generator drive packages.
Industrial pump units.
Construction equipment.
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