Isuzu 6SD1T Specifications
| Engine Model: Isuzu 6SD1T |
| Engine Type: 4-stroke in-line 6-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 600.5 cu.in (9.8 L) |
| Rated Engine Power: 270-316 Hp (201-235 kW) at 2000 rpm |
| Fuel System Type: Direct injection |
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The Isuzu 6SD1T is a heavy-duty, 9.8-liter
inline-six cylinder diesel engine from Isuzu’s S-Series family, produced
from the late 1990s through the 2000s. This engine utilizes a
turbocharged induction system with an overhead camshaft (OHC) design,
offering improved valvetrain precision and reduced maintenance compared
to older pushrod configurations. The 6SD1T was engineered for
severe-duty applications including heavy trucks such as the Isuzu Giga
and C-Series, large buses, and industrial machinery like excavators and
generator sets. A variant designated 6SD1-TC adds a turbocharger with an
intercooler for increased power density and thermal efficiency.
The 6SD1T combines a large displacement architecture with modern direct
injection to achieve high torque at reduced engine speeds. The bore and
stroke dimensions of 120 mm by 145 mm produce a bore/stroke ratio of
0.83:1, a distinctly undersquare configuration favoring torque
production over high-rpm power. The compression ratio of 16.5:1 to
16.8:1 enables efficient cold starting and stable combustion under
turbocharged boost pressures.
Dry-type chrome-plated cylinder liners provide exceptional wear
resistance and field replaceability. An inline mechanical fuel injection
pump (Bosch design) with a variable-speed mechanical governor ensures
fuel delivery precision, while later electronic variants offer enhanced
emissions control. With a dry weight of 693 kg (1,528 lb) for the
industrial version, the engine provides necessary structural rigidity
for frame-mounted installations.
Engine Type: 4-stroke, inline, turbocharged, diesel
Engine Code: 6SD1T (AA-6SD1T industrial variant)
Configuration: Vertical inline, water-cooled, 6-cylinder, overhead
camshaft
Displacement: 9.839 L (9,839 cc / 600 cu.in)
Bore: 120 mm (4.724 in)
Stroke: 145 mm (5.709 in)
Bore/Stroke Ratio: 0.83:1 (undersquare, long-stroke configuration)
Compression Ratio: 16.5:1 - 16.8:1 depending on variant
Firing Order: 1-5-3-6-2-4
Aspiration: Turbo (6SD1T) or Turbocharged and Intercooled (6SD1-TC)
Maximum Power (6SD1-T): 201 kW (270 hp) at 2,200 rpm
Maximum Power (6SD1-TC): 235 kW (316 hp) at 2,000 rpm
Maximum Torque (6SD1-T): 980 Nm (723 lb-ft) at 1,400 rpm
Maximum Torque (6SD1-TC): 1,177 Nm (868 lb-ft) at 1,400 rpm
Governed Speed: Mechanically governed, variable speed type
Combustion System: Direct injection
The cylinder block is constructed from cast iron with a deep-skirt
design, providing rigidity for the seven main bearing supports. Dry-type
chrome-plated cylinder liners are pressed into the block, offering high
wear resistance and allowing replacement during overhaul without block
machining. The liners do not contact coolant directly; instead, heat
transfers through the liner wall to the surrounding block water jacket.
An integral gear train housing at the front contains the camshaft drive,
injection pump drive, and auxiliary equipment mounts. The crankcase
incorporates piston cooling oil jets directed at the underside of each
piston crown. The block includes mounting provisions for a water-cooled
oil cooler mounted internally on the side.
The cylinder head is a cast iron cross-flow design utilizing an overhead
camshaft (OHC) with valve actuation via bucket tappets or rocker arms
depending on production revision. Each cylinder employs four valves: two
intake and two exhaust.
This configuration enhances volumetric efficiency and permits central
injector placement within the combustion chamber. Valve lash adjustment
is performed manually. The combustion chamber is a re-entrant type
direct injection design optimized for swirl generation. Valve seats are
induction-hardened for extended service life.
Intake Valve Clearance (cold): 0.40 mm (0.016 in)
Exhaust Valve Clearance (cold): 0.40 mm (0.016 in)
Valve Timing (AA-6SD1T)
Intake Valve Opens: 15° BTDC
Intake Valve Closes: 39° ATDC
Exhaust Valve Opens: 40° BTDC
Exhaust Valve Closes: 14° ATDC
The fuel system employs an in-line mechanical injection pump
manufactured by Bosch, mounted to the engine timing gear housing. The
pump is a plunger-type design with one plunger and barrel assembly per
cylinder. A variable-speed mechanical governor of the RSV type controls
fuel delivery based on engine speed and load demand. Injection timing is
set at 7° BTDC.
High-pressure injection lines route fuel from the pump to multi-hole
injection nozzles. Nozzle opening pressure is set between 17.7 and 22.1
MPa (180-225 kg/cm2 / 2,570-3,200 psi). Later TC variants may
incorporate electronic governor control or common rail systems. A fuel
transfer pump mounted to the injection pump body draws fuel from the
tank through primary and secondary filters.
The lubrication system operates as a forced circulation, full-flow
filtered system with a gear-type oil pump. The oil pump, mounted at the
front of the crankshaft, draws oil through a screened pickup tube. Oil
passes through a full-flow spin-on filter mounted on the cylinder block.
Pressurized oil routes to the seven main bearings, connecting rod
bearings, camshaft bearings, and valve gear. Internal piston cooling
jets receive pressurized oil for piston crown cooling. A water-cooled
oil cooler, mounted internally on the cylinder block, regulates oil
temperature. A pressure relief valve maintains system pressure.
Oil Capacity (oil pan only): 25.0 L (26.4 qt) min, 30.0 L (31.7 qt) max
Total System Capacity: 30.0 L (31.7 qt) min, 35.0 L (37.0 qt) max
Recommended Oil: API Service Classification CD or Isuzu Besco S-3
The cooling system is pressurized and liquid-cooled, utilizing a
belt-driven centrifugal water pump. Coolant circulates from the radiator
bottom tank through the water pump, into the cylinder block water
jacket, upward through the cylinder head, and back to the radiator top
tank.
A wax-type thermostat in the coolant outlet housing maintains operating
temperature. A six-blade sucker-type fan, 850 mm diameter, is
belt-driven from the water pump pulley. The internally mounted oil
cooler uses engine coolant as the heat exchange medium.
Coolant Capacity (engine only): 19.0 L (20.1 qt)
Coolant Type: Ethylene glycol-based with supplemental coolant additives
Thermostat Opening Temperature: 82-88°C (180-190°F)
Turbocharging System: Single exhaust-driven turbocharger mounted to the
exhaust manifold. The TC variant includes an air-to-air or air-to-water
intercooler between the turbocharger compressor outlet and intake
manifold.
Electrical System: 24-volt direct current, standard for heavy-duty Isuzu
trucks.
Starting System: Electric starter motor, 24V - 5.5 kW rating.
Charging System: Alternator, 24V - 50A rating.
Air Intake System: Dry-type replaceable element air cleaner with
restriction indicator.
Crankcase Ventilation: Closed system with breather.
Exhaust System: Cast iron exhaust manifold with turbocharger mounting
flange.
Overall Length: 1,379 mm (54.3 in)
Overall Width: 859 mm (33.8 in)
Overall Height: 1,158 mm (45.6 in)
Dry Weight: 693 kg (1,528 lb) for AA-6SD1T industrial variant
Marine Variant Weight: 1,195-1,220 kg (2,635-2,690 lb)
Engine Oil Capacity (oil pan only): 25.0-30.0 L (26.4-31.7 qt).
Total Lubrication System Capacity: 30.0-35.0 L (31.7-37.0 qt).
Coolant Capacity (engine only): 19.0 L (20.1 qt) .
Engine Oil Type: API CD, CE, CF-4, or Isuzu Besco S-3.
Coolant Type: Ethylene glycol-based anti-freeze with corrosion
inhibitors.
Oil Change Interval: 500 hours or 25,000 km (15,500 miles).
Fuel Injection Pressure (nozzle opening): 17.7-22.1 MPa (2,570-3,200
psi).
Fuel Injection Timing: 7° BTDC.
Compression Pressure (warm, 200 rpm): 2.84 MPa (412 psi).
Valve Clearance Adjustment Interval: 1,000 hours.
Valve Clearance (cold, intake): 0.40 mm (0.016 in).
Valve Clearance (cold, exhaust): 0.40 mm (0.016 in).
Cylinder Head Bolts (Stage 1): 68 Nm (50 lb-ft)
Cylinder Head Bolts (Stage 2): 88 Nm (65 lb-ft)
Connecting Rod Bolts: 38 Nm (28 lb-ft)
Main Bearing Bolts (Stage 1): 98 Nm (72 lb-ft)
Main Bearing Bolts (Stage 2): 147 Nm (108 lb-ft)
Flywheel Bolts (to crankshaft flange): 180 Nm (133 lb-ft)
Flywheel Housing to Block Bolts: 65 Nm (48 lb-ft)
Camshaft Bearing Caps: 25 Nm (18 lb-ft)
Injector Clamp Nuts (mechanical): 40 Nm (30 lb-ft)
Injector Hold-down Bolts (common rail): 15 Nm (11 lb-ft)
High-pressure Fuel Lines (fitting nuts): 30 Nm (22 lb-ft)
Valve Cover Bolts (rubber gasket): 12 Nm (9 lb-ft)
Valve Cover Bolts (cork gasket): 9 Nm (7 lb-ft)
Oil Pan Bolts (M8): 22 Nm (16 lb-ft)
Oil Pan Drain Plug: 50 Nm (37 lb-ft)
Thermostat Housing Bolts: 20 Nm (15 lb-ft)
Intake Manifold Bolts: 35 Nm (26 lb-ft)
Exhaust Manifold Nuts (turbo version): 45 Nm (33 lb-ft)
Turbocharger Mounting to Manifold: 60 Nm (44 lb-ft)
Front Crankshaft Pulley Bolt: 450 Nm (332 lb-ft) or 250 Nm (184 lb-ft)
The Isuzu 6SD1T and 6SD1-TC engines were installed in the following
equipment.
Isuzu CXZ Series: Heavy-duty trucks.
Isuzu CYZ Series: Heavy-duty trucks.
Isuzu EXZ Series: Heavy-duty trucks (Giga).
Isuzu LV132 / LT423: Large buses.
Isuzu LV4 / LV1: Bus chassis.
Sumitomo Excavators: Large hydraulic excavators.
Case Heavy Excavators: Construction machinery.
JCB JS460: Hydraulic excavator (AA-6SD1T variant).
Marine Propulsion: UM6SD1TCZ, UM6SD1TCXG, UM6SD1TCV2, UM6SD1TCG2.
Generator Sets: Stationary power generation.
Industrial Power Units: Stationary industrial applications.
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