Isuzu RZ4E Specifications
| Engine Model: Isuzu RZ4E |
| Engine Type: 4-stroke inline 4-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 115.8 cu.in (1.89 L) |
| Rated Engine Power: 120-163 Hp (88-120 kW) at 3600 rpm |
| Fuel System Type: Common Rail Direct Injection |
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The Isuzu RZ4E, marketed as the 1.9L Ddi Blue
Power, is a modern downsized 4-cylinder turbodiesel engine replacing the
larger 2.5-liter 4JK1 unit. Developed over four years of research, this
power unit prioritizes reduced weight, lower friction, and enhanced fuel
efficiency without sacrificing power delivery. The engine achieves a
mass of approximately 195 kg, representing a 56-60 kg reduction compared
to its predecessor.
Key innovations include Diamond-Like Carbon (DLC) coatings on piston
pins and injector needles, a fracture-split connecting rod design, and a
water-cooled Variable Geometry System (VGS) turbocharger. The RZ4E
complies with Euro 4 and stringent China 6b emission standards,
utilizing a high-pressure common rail system with a clothoid curve
combustion chamber. This engine primarily serves in the Isuzu D-Max
pickup, Isuzu MU-X SUV, and specific light commercial N-Series trucks.
Engine Type: Inline 4-cylinder, 4-stroke, water-cooled, turbocharged
diesel
Displacement: 1898 cc (115.8 cu.in)
Bore x Stroke: 80.0 mm x 94.4 mm (3.15 in x 3.72 in)
Compression Ratio: 16.5:1 (15.9:1 on generator or commercial variants)
Valvetrain: DOHC, 16 valves total (4 per cylinder)
Firing Order: 1-3-4-2
Maximum Power (Automotive): 110-120 kW (148-163 hp) at 3600 rpm
Maximum Power (N-Series Commercial): 88 kW (120 hp) at 3000-3200 rpm
Maximum Torque (Automotive): 350-360 Nm (258-266 lb-ft) at 1800-2600 rpm
Maximum Torque (N-Series Commercial): 320 Nm (236 lb-ft) at 1600-2000
rpm
Aspiration: Variable Geometry Turbocharger with air-to-air intercooler
Emission Standard: Euro 4 / China 6b
The cylinder block features a dual-material construction strategy. An
upper crankcase section is manufactured from cast iron for structural
rigidity and noise suppression. A deep aluminum lower oil pan reduces
overall weight. The bores utilize "melt-in" liners induction-hardened
directly into the parent metal instead of thick, replaceable steel
liners, optimizing heat transfer and bore roundness under load.
The block incorporates a stiffened bedplate design to support the five
main bearings, reducing vibration at the engine's rated speeds. An
integrated oil gallery supplies the piston cooling jets. The cylinder
block casting includes mounting points for the cartridge-style oil
filter housing and the single engine accessory drive belt tensioner.
The cylinder head is manufactured from high-pressure die-cast aluminum
to minimize mass over the front axle. It houses dual overhead camshafts
driven by a maintenance-free steel timing chain. The intake ports are
designed to generate high tumble flow, promoting air-fuel mixing within
the combustion chamber. The valvetrain utilizes Hydraulic Valve Lash
Adjusters (HVLA).
This system automatically maintains zero clearance across all 16 valves,
eliminating periodic manual adjustment. The rocker arms are roller-type
to reduce friction at the camshaft lobe interface. The injector needles
and piston pins receive a Diamond-Like Carbon (DLC) coating, reducing
reciprocal friction by approximately 37% compared to uncoated steel
components. Valve stem seals are positive-type on both intake and
exhaust valves.
The fuel system is a high-pressure common rail direct injection (Ddi)
system. A high-pressure pump supplies the common rail accumulator with
fuel pressures exceeding 2000 bar (29,000 psi). The system delivers up
to five injection events per combustion cycle, including pilot,
pre-main, main, and post injections. The injectors feature DLC-coated
needles for improved durability and consistent flow rates.
The combustion chamber geometry incorporates a "clothoid curve" profile
on the piston crown. This specific curvature accelerates the fuel-air
mixture preparation, reducing particulate formation. An integrated fuel
cooler prevents vapor lock in the high-pressure system. The fuel system
is fully controlled by an engine control unit utilizing inputs from
crankshaft, camshaft, boost pressure, and fuel rail pressure sensors.
The lubrication system uses a gear-type oil pump driven from the
crankshaft nose. A cartridge-type oil filter eliminates the metal
canister; only the paper element requires replacement during service,
reducing workshop waste. The system includes piston cooling: oil jets
directed at the underside of each piston crown manage thermal loads
during high-speed driving.
A water-cooled oil cooler, integrated into the oil filter housing, uses
engine coolant to regulate oil temperature. Oil pressure relief valve
limits maximum pressure to prevent seal damage during cold starts. The
engine oil capacity including filter ranges from 6.6 to 7.0 liters (7.0
to 7.4 qt) depending on the oil pan variant used in 4x2 versus 4x4
vehicle configurations.
The cooling system is a pressurized liquid-cooled design with a
belt-driven centrifugal water pump. A wax-pellet thermostat begins
opening at 82°C (180°F) and is fully open by 95°C (203°F). The system
features a separate circuit for exhaust gas recirculation (EGR) cooling.
The turbocharger center housing is water-cooled, utilizing a
thermosiphon circuit that continues coolant flow after engine shutdown
to prevent coking of the bearing journal.
The primary cooling fan is an electrically controlled viscous clutch
unit. Coolant capacity for the engine and radiator circuit is 7.5 liters
(7.9 qt) for D-Max applications. Coolant specification requires ethylene
glycol phosphate-free Organic Acid Technology (OAT) antifreeze. Isuzu
recommends a complete coolant replacement interval of 24 months.
Aspiration: Variable Geometry System (VGS) turbocharger. Adjustable
vanes in the turbine housing alter exhaust gas flow velocity onto the
turbine wheel. The VGS actuator is electronically controlled by the
engine control unit. The turbine wheel is manufactured from
high-temperature resistant steel alloys.
Exhaust System: Cooled Exhaust Gas Recirculation (EGR) circuit reduces
nitrogen oxide emissions. An exhaust gas recirculation cooler lowers the
temperature of recirculated gases before reintroduction to the intake
manifold. A Diesel Particulate Filter (DPF) is fitted for Euro 4 and
China 6b compliant variants. Post-injection fuel events regenerate the
DPF by raising exhaust temperatures.
Timing Drive: The camshafts are driven by a single-stage steel roller
chain. This chain operates in an oil bath and is sealed behind a pressed
steel cover. The design requires no routine replacement under normal
driving conditions. A separate chain drives the oil pump from the
crankshaft.
Electrical System: 12 V negative ground. Starter motor power rating is
1.8 kW (M12 mounting bolts at 97 Nm / 72 lb-ft). Alternator output
ranges from 90 A to 150 A depending on vehicle specification. Glow plugs
operate at 12 V with ceramic heating elements for rapid temperature
rise.
Length (flywheel to front pulley): 635 mm (25.0 in)
Width (overall, exhaust manifold to injection pump): 580 mm (22.8 in)
Height (oil pan rail to rocker cover): 670 mm (26.4 in)
Dry Engine Weight (fully dressed without fluids): 195 kg (430 lb)
Dry Engine Weight (basic, no alternator or starter): 175 kg (386 lb)
Engine Oil Change Interval: 10,000 km (6,200 miles) or 12 months.
Engine Oil Capacity (including filter): 6.6-7.0 L (7.0-7.4 qt).
Engine Oil Grade: API CJ-4, CK-4, or ACEA E9. SAE 5W-30, 10W-40, or
0W-20.
Engine Oil Pressure at Rated Speed: 2.5-4.5 bar (36-65 psi).
Engine Oil Pressure at Low Idle (min): 0.8 bar (12 psi) at operating
temperature.
Coolant Capacity (engine + radiator): 7.5 L (7.9 qt).
Coolant Specification: Phosphate-free OAT, ethylene glycol base.
Coolant Replacement Interval: 24 months.
Thermostat Opening Temperature: 82°C (180°F).
Fuel Filter Replacement Interval: 20,000 km (12,400 miles).
Fuel Filter Water Separator: Drain every 5,000 km (3,100 miles).
Air Filter Replacement Interval: 40,000 km (25,000 miles).
Cartridge Oil Filter Element Replacement: Every oil change.
Valve Clearance: Hydraulic Valve Lash Adjusters (HVLA).
Drive Belt (single accessory belt) Tension: Automatic spring tensioner.
Drive Belt (single accessory belt) Replacement: Every 100,000 km (62,000
miles).
Glow Plug Resistance (cold): 0.6-0.9 ohm per plug.
Compression Pressure (standard): 2.9-3.5 MPa (420-508 psi) at 250 rpm.
Compression Pressure (minimum): 2.4 MPa (348 psi).
Compression Pressure Maximum variation between cylinders 0.2 MPa (29
psi).
Cylinder Head Bolts (Stage 1): 30 Nm (22 lb-ft)
Cylinder Head Bolts (Stage 2): 90 Nm (66 lb-ft)
Connecting Rod Cap Bolts: 30 Nm (22 lb-ft)
Main Bearing Cap Bolts: 40 Nm (30 lb-ft)
Main Bearing Bedplate Bolts (M8): 25 Nm (18 lb-ft)
Flywheel Bolts (to crankshaft flange): 50 Nm (37 lb-ft)
Flywheel Housing Bolts (to block, M10): 52 Nm (38 lb-ft)
Flywheel Housing Bolts (to block, M12): 97 Nm (72 lb-ft)
Camshaft Bearing Cap Bolts: 12 Nm (9 lb-ft)
Camshaft Timing Gear Bolt: 100 Nm (74 lb-ft)
Injector Clamp Bolt: 25 Nm (18 lb-ft)
High-Pressure Pump Mounting Bolts: 40 Nm (30 lb-ft)
Common Rail Mounting Bolts: 22 Nm (16 lb-ft)
High-Pressure Fuel Line Nuts: 35 Nm (26 lb-ft)
Crankshaft Pulley Bolt (center): 180 Nm (133 lb-ft)
Oil Pan Drain Plug: 83 Nm (61 lb-ft)
Oil Pan Bolts (M8): 25 Nm (18 lb-ft)
Oil Filter Cartridge Cap: 25 Nm (18 lb-ft)
Oil Level Gauge Guide Tube Nut: 25 Nm (18 lb-ft)
Water Pump Mounting Bolts: 22 Nm (16 lb-ft)
Thermostat Housing Bolts: 12 Nm (9 lb-ft)
Starter Motor Mounting Bolts (M10): 52 Nm (38 lb-ft)
Starter Motor Mounting Bolts (M12): 97 Nm (72 lb-ft)
Starter Motor B-terminal Nut: 10 Nm (89 lb-in)
Alternator Mounting Bolt: 45 Nm (33 lb-ft)
Alternator Pivot Bolt: 55 Nm (41 lb-ft)
Glow Plug: 18 Nm (13 lb-ft)
Exhaust Manifold Nuts: 35 Nm (26 lb-ft)
Turbocharger Mounting Nuts (to manifold): 45 Nm (33 lb-ft)
Engine Mount Bracket Bolts (to block): 70 Nm (52 lb-ft)
Isuzu D-Max (2018-present): Single Cab, Space Cab, and Crew Cab body
styles. 4x2 and 4x4 drivetrain configurations. Six-speed manual or
six-speed automatic transmissions. Markets include Philippines,
Thailand, Australia, China (Jiangling Motors joint venture), and Latin
America.
Isuzu MU-X (2018-present): Mid-size SUV with three-row seating. LS,
LS-A, and top-tier trim levels. Introduced initially in Philippines
before global rollout.
Isuzu N-Series (NHR models): Light-duty commercial trucks rated at 3.5
tonnes GVWR. RZ4EER-T variant rated at 120 PS (88 kW) for urban delivery
applications. Available primarily in Asian markets including Hong Kong
and Japan.
Commercial Variants: Stationary generator sets (20-30 kVA range).
Agricultural irrigation pump drives. Marine auxiliary power units for
small vessels.
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