Hyundai D4AL Specifications
| Engine Model: Hyundai D4AL |
| Engine Type: 4-cycle inline 4-cylinder OHV 8-valve turbocharged liquid-cooled diesel |
| Total Displacement: 201.3 cu.in (3.29 L) |
| Rated Engine Power: 115-120 Hp (85-88 kW) at 3400 rpm |
| Fuel System Type: Direct injection |
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The Hyundai D4AL is a 3.3-liter, inline-4 turbocharged
diesel engine developed for light-duty commercial applications. Based on
Mitsubishi’s 4D31 and 4D32 designs, this powerplant served as the primary
propulsion unit for Hyundai’s medium-duty truck range and passenger bus variants
throughout the 1990s and early 2000s. Engineered for durability under sustained
high-load operation, the D4AL combines a robust overhead valve (OHV)
architecture with mechanical direct injection, prioritizing serviceability and
operational longevity over electronic complexity.
The Hyundai D4AL represents a commercial-grade diesel engine designed for
applications demanding high torque output at low engine speeds and exceptional
service life. Its lineage traces directly to Mitsubishi heavy-duty diesel
architecture, inheriting a fully cast iron construction with gear-driven
valvetrain, eliminating the vulnerability associated with belt or chain timing
systems. The OHV configuration with two valves per cylinder provides a compact
cylinder head design with reduced complexity compared to overhead camshaft
alternatives.
The inline injection pump and mechanical fuel system operate independently of
electronic controls, facilitating repair and maintenance in regions with limited
diagnostic infrastructure. The engine’s torque characteristics peak at 2,000
rpm, delivering the low-end pulling power essential for laden truck operation
and stop-start commercial duty cycles. The robust construction results in
increased mass and physical dimensions relative to passenger car engines,
reflecting its commercial application focus.
Engine Type: Inline 4-cylinder, 4-stroke cycle, water-cooled, turbocharged
diesel.
Displacement: 3,298 cc (201.3 cu.in).
Bore x Stroke: 100.0 mm x 105.0 mm (3.94 in x 4.13 in).
Compression Ratio: 16.5:1 for Euro I and Euro II emission variants.
Firing Order: 1-3-4-2.
Aspiration: Turbocharged. Select variants incorporate an air-to-air intercooler.
Maximum Power: 115-120 hp (85-88 kW) @ 3,400 rpm.
Maximum Torque: 284-294 Nm (209-217 lb-ft) @ 2,000 rpm.
Idle Speed: 750 ± 25 rpm.
Valvetrain: OHV, 8 valves (2 valves per cylinder).
Pushrod-actuated with mechanical valve adjusters.
The cylinder block is constructed from high-strength
cast iron with a deep-skirt design extending below the crankshaft centerline to
maximize rigidity under high cylinder pressures. The block is of monobloc
construction with integral cylinder bores, each bore induction-hardened to
resist wear under extended service intervals. Seven main bearings support the
crankshaft, providing exceptional support for the rotating assembly under
sustained high torque loads.
The block incorporates an integrated timing gear housing at the front face,
housing the camshaft drive gears and injection pump drive gears. Water jackets
are designed with generous coolant passages to manage thermal loads associated
with turbocharged diesel operation in commercial duty cycles. The block features
mounting provisions for the inline injection pump, air compressor, and power
steering pump.
The cylinder head is manufactured from cast iron,
selected for its thermal stability and resistance to distortion under the
elevated cylinder pressures of turbocharged diesel combustion. It employs an OHV
configuration with the camshaft located within the cylinder block. The valve
arrangement consists of two valves per cylinder positioned in a vertical
orientation. Intake and exhaust valves are actuated by pushrods and rocker arms
operating from the block-mounted camshaft.
The combustion chamber is of the direct injection type with a re-entrant bowl
machined into the piston crown. Valve seats are induction-hardened or fitted
with replaceable inserts to withstand the high temperatures of diesel
combustion. The cylinder head incorporates separate intake and exhaust ports on
opposite sides, with the exhaust manifold integrated into the turbocharger
mounting interface.
The fuel system is a mechanical direct injection
configuration utilizing an in-line injection pump, commonly of Bosch A-type or
licensed manufacture. The pump is gear-driven from the timing gear train and
mounted to the cylinder block. Each cylinder receives fuel from a dedicated pump
element, with injection timing and fuel quantity regulated by the pump’s
internal governor system. Injection nozzles are of the multi-hole type,
installed in each cylinder and sealed with copper gaskets.
Nozzle opening pressure is calibrated to approximately 150-160 bar (2,175-2,320
psi). A mechanical governor controls idle speed and maximum engine speed, with a
manual stop cable or solenoid for engine shutdown. Fuel delivery is supplemented
by a lift pump mounted to the injection pump body, drawing fuel through a
primary filter and water separator assembly. Excess fuel returns to the tank via
a spill rail.
The lubrication system is a pressurized, wet-sump
configuration designed for the extended operating cycles of commercial
applications. A gear-type oil pump, driven by the crankshaft timing gear,
circulates oil through a full-flow disposable filter. An integral oil cooler, of
the water-to-oil type, maintains oil temperature within operational limits under
sustained high-load conditions. The system incorporates a large-capacity sump
ranging from 9.0 to 9.5 liters depending on the vehicle application and oil pan
configuration.
Oil galleries within the cylinder block and cylinder head supply pressurized oil
to the seven main bearings, connecting rod bearings, camshaft bearings, and
rocker arm assemblies. The turbocharger receives oil through a dedicated supply
line with a restrictor fitting to regulate flow, returning oil via a gravity
drain to the sump. A pressure relief valve maintains system pressure within
specified limits.
The cooling system is a pressurized, water-cooled
design with capacity to manage the thermal output of a turbocharged diesel
engine operating in commercial duty cycles. A belt-driven water pump circulates
coolant through the cylinder block, cylinder head, and radiator. A wax-type
thermostat, beginning to open at 76-82°C (169-180°F), regulates coolant flow to
maintain operating temperature.
The radiator is a cross-flow type with high-density core construction, often
supplemented by a coolant recovery reservoir. A viscous fan coupling drives the
engine cooling fan, providing variable fan speed proportional to engine
temperature and reducing parasitic losses during low-load operation. The system
is designed to accommodate additional coolant capacity for heater circuits in
bus and passenger configurations.
Glow Plug System: The engine is equipped with a glow
plug system for cold-start assistance. Glow plugs are installed in the cylinder
head adjacent to each injector, controlled by a glow timer or control unit that
modulates pre-heat duration based on coolant temperature. After-glow operation
supports cold-idle stability following start-up.
Timing System: The camshaft, injection pump, and accessory drives are driven by
a gear train housed at the front of the engine. The camshaft is driven directly
from the crankshaft timing gear, with the injection pump and power steering pump
driven via idler gears. This gear-driven arrangement eliminates the need for
timing belt or chain replacement, providing exceptional durability.
Turbocharger System: A fixed-geometry turbocharger provides forced induction.
The turbocharger is mounted to the exhaust manifold, with boost pressure
regulated by a wastegate actuator. Intercooled variants incorporate an
air-to-air charge cooler mounted forward of the radiator to increase charge air
density.
Emission Control: The engine incorporates a positive crankcase ventilation (PCV)
system and, on later variants, an exhaust gas recirculation (EGR) valve to meet
Euro I and Euro II emission standards. A fuel injection timing adjustment
mechanism allows for calibration to specific emission requirements.
Air Compressor: Commercial vehicle variants are equipped with a single-cylinder
air compressor driven by the timing gear train, providing compressed air for
brake and suspension systems on truck and bus applications.
Electrical System: The charging system consists of a 12-volt, 90-110 amp
alternator. The starter motor is a high-torque unit with a 3.0 kW (4.0 hp)
rating, designed to crank the engine against its high compression ratio in cold
conditions.
Dry Weight: 380 kg (838 lb), including turbocharger and
injection pump.
Overall Length (from accessory drive to flywheel housing): 920 mm (36.2 in).
Overall Width: 730 mm (28.7 in).
Overall Height: 880 mm (34.6 in).
Engine Oil Capacity (total system): 9.3 liters (9.8
qt), including filter and oil cooler.
Engine Oil Specification: SAE 15W-40 meeting API CD, CE, CF, or higher
Engine Oil Pressure (at idle): Minimum 0.7 bar (10 psi).
Engine Oil Pressure (at 2,500 rpm): 3.5-4.5 bar (51-65 psi).
Coolant Capacity: 12.0-14.0 liters (12.7-14.8 qt).
Coolant Specification: Ethylene glycol-based antifreeze.
Intake Valve Clearance (Cold): 0.25-0.40 mm (0.010-0.016 in).
Exhaust Valve Clearance (Cold): 0.30-0.45 mm (0.012-0.018 in).
Valve Clearance Inspection Interval: Every 40,000 km (25,000 miles).
Compression Pressure (Standard): 2.55 MPa (370 psi) at 200 rpm cranking speed.
Compression Pressure (Minimum): allowable: 2.15 MPa (312 psi).
Compression Pressure Variation: Maximum 0.20 MPa (29 psi) between cylinders.
Injector Nozzle Opening Pressure: 150-160 bar (2,175-2,320 psi).
Glow Plug Resistance: 0.8-1.2 ohms per plug. Idle Speed: 750 ± 25 rpm.
Turbocharger Boost Pressure: 0.5-0.7 bar (7-10 psi) at full load.
Cylinder Head Bolts (M18): 175 Nm (129 lb-ft).
Main Bearing Cap Bolts: 100 Nm (74 lb-ft).
Connecting Rod Bolts: 39 Nm (29 lb-ft) plus 40°.
Camshaft Thrust Plate Bolts: 20-25 Nm (15-18 lb-ft).
Camshaft Gear Bolt: 80-90 Nm (59-66 lb-ft).
Flywheel Bolts: 123 Nm (91 lb-ft).
Crankshaft Pulley Nut: 586 Nm (432 lb-ft).
Crankshaft Timing Gear Bolt: 250-270 Nm (184-199 lb-ft).
Injection Pump Mounting Nuts: 20-25 Nm (15-18 lb-ft).
Injection Pump Drive Gear Bolt: 55-60 Nm (41-44 lb-ft).
Injector Hold-Down Clamp Bolts: 25-30 Nm (18-22 lb-ft).
Glow Plugs: 25-30 Nm (18-22 lb-ft).
Intake Manifold Nuts: 25-30 Nm (18-22 lb-ft).
Exhaust Manifold Nuts: 35-40 Nm (26-30 lb-ft).
Turbocharger Mounting Nuts: 40-45 Nm (30-33 lb-ft).
Rocker Arm Shaft Bracket Bolts: 30-35 Nm (22-26 lb-ft).
Valve Cover Bolts: 8-10 Nm (6-7 lb-ft).
Oil Pan Bolts: 10-12 Nm (7-9 lb-ft).
Oil Pump Mounting Bolts: 20-25 Nm (15-18 lb-ft).
Water Pump Mounting Bolts: 20-25 Nm (15-18 lb-ft).
Engine Mount (Bracket to Block): 70-80 Nm (52-59 lb-ft).
The Hyundai D4AL engine was utilized across a range of
light-duty and medium-duty commercial vehicles during its production lifecycle.
Hyundai Mighty (HD65, HD72 Series): 1993-2004, the D4AL served as the primary
powerplant for these light-duty trucks in domestic Korean and export markets,
including Southeast Asia, Latin America, and Africa.
Hyundai County (Bus): 1998-2004, this mid-size bus platform utilized the D4AL
engine in both standard and intercooled configurations for passenger transport
applications.
Hyundai HD Series (HD65, HD72): The engine continued in production for
commercial truck applications throughout the late 1990s and early 2000s, meeting
Euro I and Euro II emission standards.
Hyundai H100 (Heavy-Duty Variants): Select heavy-duty configurations of the H100
truck platform in certain markets received the D4AL engine as an upgraded
powerplant option.
Kia Rhino / K-Series Trucks: Licensed variants of the D4AL were utilized in
Kia-branded medium-duty trucks sharing platform architecture with Hyundai
commercial vehicles.
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