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Doosan D18 Engine

The Doosan D18 is a compact, industrial-grade 3-cylinder, 4-cycle inline diesel engine engineered by Doosan Infracore. Commonly integrated into generator powerpacks, construction machinery, and industrial equipment, it conforms to strict modern emissions frameworks including Stage V and Tier 4 Final mandates. The engine utilizes a heavy-duty architecture characterized by water-cooling, turbocharging, and air-to-air aftercooling to maximize thermal efficiency and structural durability in demanding environments.

The valve mechanism features a overhead configuration controlled via an overhead camshaft or pushrod assembly, built specifically to sustain high-pressure induction. The intake and exhaust valves are precisely timed to manage optimized airflow across the 3-cylinder array, ensuring clean exhaust output and reliable combustion metrics. Bore: 90 mm. Stroke: 94 mm. Total Displacement: 1.794 Liters. Compression Ratio: 17.0:1. The engine uses a full-pressure lubrication loop managed by an internal oil pump. Thermal regulation uses a freshwater forced circulation system driven by a belt-driven centrifugal water pump.

Fuel delivery relies entirely on a high-pressure Bosch common-rail direct injection (CRDI) system. This configuration leverages precise electronic control units (ECUs) to meter multi-stage fuel injection sequences under extreme pressure, maximizing power extraction and ensuring ultra-low emission compliance. The system mandates the strict use of Ultra-Low Sulfur Diesel (ULSD) fuel with a maximum threshold of 15 ppm sulfur content to protect downstream diesel particulate filter elements.

General Technical Data

Engine Specifications

Engine Model ............... Doosan D18 (D18NAP)
Engine Type ............... 4-cycle inline 3-cylinder electronic common-rail liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.54 (90.0)
Engine Stroke, in (mm) ............... 3.70 (94.0)
Displacement, cu.in (L) ............... 109.5 (1.794)
Rated Engine Power, hp (kW) ............... 49-50 (36.6-37.0) at 2800 rpm
Rated Engine Speed, rpm ............... 2400-2800
Peak Torque ............... 165 Nm (122 lb-ft) at 1600 rpm
Idle Speed ............... 800-950 rpm
Aspiration Type ............... Turbocharged and air-to-air aftercooled
Operating Speed ............... 1500-2800 rpm
Compression Ratio ............... 17.0:1
Firing Order ............... 1-3-2
Valve Configuration ............... Overhead valve (OHV) with hydraulic valve lash adjusters
Cylinder Block Type ............... Cast iron
Cylinder Head Type ............... Cast iron
Lubrication System ............... Full-pressure force-feed
Oil Pump Type ............... Gear-driven
Oil Filter Type ............... Full-flow, spin-on cartridge
Cooling System ............... Liquid-cooled with fresh water forced circulation
Water Pump Type ............... Belt-driven, centrifugal
Air Cleaner Type ............... Dry dual-element
Emission Certification ............... Tier 4 Final / Stage V compliant
Aftertreatment System ............... Diesel Oxidation Catalyst (DOC) without DPF
Starting System ............... Electric Starter Motor
Electrical System ............... 12V
Alternator Capacity ............... 110A
Starter Motor Power ............... 2.5 kW

Fuel System

Fuel Injection Pump Type ............... Bosch high-pressure common rail electronic pump
System Fuel Pressure, bar (psi) ............... 250-1800 (3625-26107)
Fuel Injector Type ............... Electronically controlled solenoid injector assembly
Fuel Transfer Pump Type ............... Mechanical gear pump integrated into high-pressure unit
Primary Fuel Filter Type ............... Water separator with manual drain valve
Secondary Fuel Filter Type ............... High-efficiency spin-on micro-filter cartridge
Fuel Return Rate, L/hr (gal/hr) ............... 45.0-60.0 (11.8-15.8) at rated output
Maximum Fuel Inlet Restriction, kPa (in.Hg) ............... 15.0 (4.4)
Maximum Fuel Return Restriction, kPa (in.Hg) ............... 30.0 (8.8)
Governor Type ............... Full electronic engine control unit (ECU)
Recommended Fuel Grade ............... Ultra-Low Sulfur Diesel (ULSD) with 15 ppm max sulfur
Injection Timing Regulation ............... Variable control via electronic map profiles
Minimum Cold Start Pre-heating Duration, sec ............... 5-15
Common Rail Volume, cu.in (cc) ............... 1.22 (20.0)

Dimensions and Weight

Engine Length (DL01-LEE00), in (mm) ............... 26.5 (675)
Engine Length (DL01-LEL00), in (mm) ............... 20.2 (515)
Engine Width (DL01-LEE00), in (mm) ............... 18.8 (475)
Engine Width (DL01-LEL00), in (mm) ............... 21.3 (540)
Engine Height (DL01-LEE00), in (mm) ............... 29.0 (735)
Engine Height (DL01-LEL00), in (mm) ............... 27.4 (695)
Dry Weight (DL01-LEE00), lbs (kg) ............... 365 (165)
Dry Weight (DL01-LEL00), lbs (kg) ............... 375 (170)

Maintenance Data

Service Information

Oil Pressure at Idle Speed, bar (psi) ............... 1.0-1.5 (14.5-21.7)
Oil Pressure at Rated Speed, bar (psi) ............... 3.0-4.5 (43.5-65.2)
Thermostat Opening Temperature, F (C) ............... 180.0 (82.0)
Thermostat Full Open Temperature, F (C) ............... 203.0 (95.0)
Maximum Coolant Temperature, F (C) ............... 221.0 (105.0)

Engine Oil and Coolant

Engine Oil Type .................. SAE 5W-30, SAE 10W-30, or 10W-40
API Service Classifications ......................... CI-4 or CJ-4
Engine Oil Capacity (Maximum Pan), qt (L) ............... 6.65 (6.3)
Engine Oil Capacity (Minimum Pan), qt (L) ............... 3.17 (3.0)
Engine Coolant Capacity (Block Only), qt (L) ............... 3.27 (3.1)
Total Coolant System Capacity, qt (L) ............... 8.87 (8.4)

Service Intervals

Change oil and filter ............... Every 500 hours
Inspect air cleaner ............... Every 250 hours
Replace air cleaner ............... Every 1000 hours
Replace fuel filter ............... Every 500 hours
Valve clearance adjustment ............... Every 1000 hours
Fuel system inspection ............... Every 1000 hours
Change coolant ............... Every 2000 hours
Compression test ............... Every 1000 hours
Clean radiator core ............... Every 250 hours
Inspect belt tension ............... Every 200 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 3.5433-3.5441 (90.000-90.022)
Cylinder Bore Out-of-Roundness, in (mm) ............... 0.0002 (0.005) or lower
Cylinder Bore Taper Limit, in (mm) ............... 0.0004 (0.010)
Crankshaft Main Journal Outer Diameter, in (mm) ............... 2.5976-2.5984 (65.980-66.000)
Crankpin Journal Outer Diameter, in (mm) ............... 1.9677-1.9685 (49.980-50.000)
Main Bearing Oil Clearance, in (mm) ............... 0.0015-0.0035 (0.040-0.090)
Connecting Rod Bearing Clearance, in (mm) ............... 0.0013-0.0031 (0.035-0.080)
Crankshaft End Play, in (mm) ............... 0.0039-0.0118 (0.100-0.300)
Connecting Rod Side Play, in (mm) ............... 0.0059-0.0125 (0.150-0.320)
Connecting Rod Bushing Small End I.D, in (mm) ............... 1.1816-1.1824 (30.013-30.033)
Piston Outer Diameter, in (mm) ............... 3.5393-3.5401 (89.900-89.920)
Piston-to-Cylinder Wall Clearance, in (mm) ............... 0.0031-0.0047 (0.080-0.120)
Piston Pin Bore Inner Diameter, in (mm) ............... 1.1812-1.1815 (30.003-30.010)
Piston Pin Outer Diameter, in (mm) ............... 1.1808-1.1811 (29.993-30.000)
Top Ring Groove Width, in (mm) ............... 0.0807-0.0815 (2.050-2.070)
Second Ring Groove Width, in (mm) ............... 0.0602-0.0610 (1.530-1.550)
Oil Ring Groove Width, in (mm) ............... 0.0801-0.0809 (2.035-2.055)
Top Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.200-0.350)
Second Ring End Gap, in (mm) ............... 0.0137-0.0216 (0.350-0.550)
Oil Ring End Gap, in (mm) ............... 0.0098-0.0196 (0.250-0.500)
Top Ring Side Clearance, in (mm) ............... 0.0023-0.0043 (0.060-0.110)
Second Ring Side Clearance, in (mm) ............... 0.0015-0.0031 (0.040-0.080)
Oil Ring Side Clearance, in (mm) ............... 0.0007-0.0025 (0.020-0.065)
Cylinder Head Flatness Tolerance (Overall Surface), in (mm) ............... 0.0019 (0.050)
Cylinder Block Deck Surface Flatness, in (mm) ............... 0.0020 (0.051)
Valve Stem Outer Diameter (Intake), in (mm) ............... 0.2740-0.2748 (6.960-6.980)
Valve Stem Outer Diameter (Exhaust), in (mm) ............... 0.2728-0.2736 (6.930-6.950)
Valve Guide Inner Diameter, in (mm) ............... 0.2755-0.2763 (7.000-7.020)
Valve Stem-to-Guide Clearance (Intake), in (mm) ............... 0.0007-0.0023 (0.020-0.060)
Valve Stem-to-Guide Clearance (Exhaust), in (mm) ............... 0.0019-0.0035 (0.050-0.090)
Valve Recess Depth Position (Intake), in (mm) ............... 0.0236-0.0354 (0.600-0.900)
Valve Recess Depth Position (Exhaust), in (mm) ............... 0.0236-0.0354 (0.600-0.900)
Valve Seat Angle (Intake and Exhaust), deg ............... 45
Valve Face Angle (Intake and Exhaust), deg ............... 45
Valve Spring Free Length, in (mm) ............... 1.858 (47.20)
Camshaft Main Journal Diameters (Front), in (mm) ............... 1.8496-1.8503 (46.980-47.000)
Camshaft Main Journal Diameters (Center), in (mm) ............... 1.8102-1.8110 (45.980-46.000)
Camshaft Main Journal Diameters (Rear), in (mm) ............... 1.7708-1.7716 (44.980-45.000)
Camshaft Bearing Clearance, in (mm) ............... 0.0011-0.0035 (0.030-0.090)
Camshaft End Play, in (mm) ............... 0.0019-0.0059 (0.050-0.150)
Timing Gear Backlash (Crank-to-Cam), in (mm) ............... 0.0011-0.0043 (0.030-0.110)
Timing Gear Backlash (Cam-to-Pump), in (mm) ............... 0.0011-0.0043 (0.030-0.110)

Tightening Torques

Cylinder Head Bolts (Step One), Nm (lb-ft) ............... 39.22 (28.9)
Cylinder Head Bolts (Step Two), Rotation ............... 90+90 deg
Main Bearing Cap Bolts, Nm (lb-ft) ............... 53.90 (39.7)
Connecting Rod Cap Fasteners, Nm (lb-ft) ............... 19.60 (14.4)
Flywheel Retaining Fasteners, Nm (lb-ft) ............... 85.0 (62.6)
Flywheel Housing Assembly Bolts, Nm (lb-ft) ............... 45.0 (33.1)
Crankshaft Front Pulley Center Nut/Bolt, Nm (lb-ft) ............... 170.0 (125.3)
Camshaft Thrust Plate Screws, Nm (lb-ft) ............... 24.0 (17.7)
Camshaft Drive Gear Mounting Bolt, Nm (lb-ft) ............... 95.0 (70.0)
Timing Gear Case Fasteners, Nm (lb-ft) ............... 24.0 (17.7)
Rocker Arm Assembly Support Shaft Bolts, Nm (lb-ft) ............... 32.0 (23.6)
Cylinder Head Cover Gasket Clamp Screws, Nm (lb-ft) ............... 10.0 (7.3)
Oil Pan Sump Peripheral Mounting Bolts, Nm (lb-ft) ............... 24.0 (17.7)
Oil Pan Sump Bottom Drain Plug Bolt, Nm (lb-ft) ............... 35.0 (25.8)
Oil Pump Internal Gear Carrier Fasteners, Nm (lb-ft) ............... 24.0 (17.7)
Water Pump Backing Plate Screws, Nm (lb-ft) ............... 24.0 (17.7)
Water Pump Outer Pulley Mounting Nuts, Nm (lb-ft) ............... 24.0 (17.7)
Thermostat Cover Inlet Pipe Bolts, Nm (lb-ft) ............... 24.0 (17.7)
Intake Manifold Cylinder Head Intake Ports Bolts, Nm (lb-ft) ............... 24.0 (17.7)
Exhaust Manifold Heat Resistant Mounting Nuts, Nm (lb-ft) ............... 28.0 (20.6)
Turbocharger Housing Mounting Flange Nuts, Nm (lb-ft) ............... 28.0 (20.6)
Turbocharger High Pressure Lubrication Delivery Pipe Bolt, Nm (lb-ft) ............... 18.0 (13.2)
Turbocharger Low Pressure Lubrication Drain Tube Bolts, Nm (lb-ft) ............... 10.0 (7.3)
Common Rail Fuel Block Base Assembly Bolts, Nm (lb-ft) ............... 24.0 (17.7)
High Pressure Fuel Delivery Pipes Swivel Joint Nuts, Nm (lb-ft) ............... 27.0 (19.9)
Fuel Injector Hold Down Clamp Pivot Bracket Bolts, Nm (lb-ft) ............... 22.0 (16.2)
Fuel Injector Leakage Fluid Return Line Fixing Screws, Nm (lb-ft) ............... 12.0 (8.8)
Fuel Injection Pump Mount Stud Fixing Engine Nuts, Nm (lb-ft) ............... 24.0 (17.7)
Fuel Injection Pump Drive Spur Gear Central Nut, Nm (lb-ft) ............... 65.0 (47.9)
Oil Cooler Core Internal Module Screws, Nm (lb-ft) ............... 12.0 (8.8)
Oil Filter Center Threaded Adapter Fitting, Nm (lb-ft) ............... 45.0 (33.1)
Oil Pressure Sensor Signalling Unit Fitting, Nm (lb-ft) ............... 15.0 (11.0)
Coolant Thermal Sensor Signalling Unit Fitting, Nm (lb-ft) ............... 20.0 (14.7)
Electronic Crankshaft Position Timing Sensor Bolt, Nm (lb-ft) ............... 8.0 (5.9)
Electronic Camshaft Position Phase Tracking Sensor Bolt, Nm (lb-ft) ............... 8.0 (5.9)
Electronic Control Module Housing Support Bolts, Nm (lb-ft) ............... 10.0 (7.3)
Intake Air Heating Glow Plug Element Base Core, Nm (lb-ft) ............... 22.0 (16.2)
Intake Air Heating Element Electrical Cable Nut, Nm (lb-ft) ............... 4.0 (2.9)
Electric Starter Housing Main Engine Flange Bolts, Nm (lb-ft) ............... 45.0 (33.1)
Electric Starter Rear Support Frame Bracket Bolt, Nm (lb-ft) ............... 24.0 (17.7)
Alternator Pivot Mounting Support Bolt, Nm (lb-ft) ............... 45.0 (33.1)
Alternator Variable Tensioning Link Bolt, Nm (lb-ft) ............... 24.0 (17.7)
Exhaust Gas Recirculation Cooler Rigid Mount Bolts, Nm (lb-ft) ............... 24.0 (17.7)
Exhaust Gas Recirculation Flow Control Valve Bolts, Nm (lb-ft) ............... 24.0 (17.7)
Exhaust Gas Recirculation Interconnecting Flange Screws, Nm (lb-ft) ............... 24.0 (17.7)
Crankcase Breather Separation Unit Plastic Cover Screws, Nm (lb-ft) ............... 10.0 (7.3)
Main Front Rubber Isolated Engine Mount Brackets, Nm (lb-ft) ............... 85.0 (62.6)
Rear Flywheel Base Chassis Support Brackets, Nm (lb-ft) ............... 85.0 (62.6)

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