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Yanmar 4TN78T Engine

General Technical Data

Yanmar 4TN78T Engine Specs

Engine Model ................ Yanmar 4TN78T
Engine Type ................ 4-Cycle direct injection turbocharger diesel
Number of Cylinders ................ 4
Cylinder Bore, mm (in) ................ 78.0 (3.07)
Piston Stroke, mm (in) ................ 86.0 (3.39)
Total Displacement, L (cu.in) ................ 1.64 (100.05)
Rated Engine Power, kW (hp) ................ 29.0 (39.0)
Fast Idle Speed, rpm ................ 2750
Slow Idle Speed, rpm ................ 800
Aspiration Type ................ Turbocharger
Crankshaft Alignment ................ Horizontal
Compression Ratio ................ 17.75:1
Firing Order ................ 1-3-4-2
Air Cleaner ................ Dry element with precleaner
Lubrication System ................ Full pressure
Oil Filter Type ................ Full flow, replaceable
Electrical System Rating, Volts ................ 12
Charging System ................ Alternator
Alternator Rating, Amps ................ 25

Fuel System

Fuel System ................ Direct injection
Injection Pump Timing, deg ................ 14, BTDC
Governor Type ................ Mechanical
Fuel Injection Nozzle Pressure, kPa (psi) ................ 19600±480 (2843±70)
Fuel Supply Pump Pressure, kPa (psi) ................ 29 (4.3)

Yanmar 4TN78T Maintenance

Service Data

Cylinder bore inside diameter, mm (in) ................ 78.00-78.03 (3.071-3.072)
Cylinder head (max out of flatness), mm (in) ................ 0.05 (0.002)
Intake valve clearance (Cold), mm (in) ................ 0.20 (0.008)
Exhaust valve clearance (Cold), mm (in) ................ 0.20 (0.008)
Cylinder compression, kPa (psi) ................ 2448 (355)
Engine oil pressure, kPa (psi) ................ 214-345 (31-50)
Fan belt tension, N (lbf) ................ 98 (22)
Fan belt deflection, mm (in) ................ 10-15 (0.40-0.60)

Engine Oil and Filters

Engine oil type ................ SAE 10W-30, 15W-40, 5W-30
API service classification ................ CE or CD
Engine oil capacity, L (qts) ................ 7.5 (8.0)
Oil filter part number ................ 129150-35150
Air filter part number ................ 129150-12510
Fuel filter part number ................ 129100-55650

Yanmar 4TN78T Service Specifications

Cylinder Block

Cylinder Bore Clearance, mm (in) ................ 0.22 (0.009)
Cylinder Bore I.D (Std), mm (in) ................ 78.00-78.03 (3.071-3.072)
Cylinder Bore I.D (Wear Limit), mm (in) ................ 78.20 (3.079)
Cylinder Bore I.D (0.25 mm Oversize), mm (in) ................ 78.25-78.28 (3.081-3.082)
Cylinder Bore I.D (0.50 mm Oversize), mm (in) ................ 78.50-78.53 (3.091-3.092)
Crankshaft End Play, mm (in) ................ 0.090-0.271 (0.004-0.011)
Connecting Rod Journal O.D (Std), mm (in) ................ 42.952-42.962 (1.6910-1.6914)
Connecting Rod Journal O.D (Wear Limit), mm (in) ................ 42.91 (1.689)
Connecting Rod Bearing Clearance, mm (in) ................ 0.16 (0.006)
Connecting Rod Bearing I.D (Std), mm (in) ................ 43.00-43.042 (1.693-1.695)
Connecting Rod Bearing I.D (Wear Limit), mm (in) ................ 43.07 (1.696)
Main Bearing Journal O.D (Std), mm (in) ................ 46.952-46.962 (1.8485-1.8489)
Main Bearing Journal O.D (Wear Limit), mm (in) ................ 46.91 (1.847)
Main Bearing Clearance, mm (in) ................ 0.15 (0.0059)
Main Bearing I.D (Std), mm (in) ................ 47.00-47.045 (1.850-1.852)
Main Bearing I.D (Wear Limit), mm (in) ................ 47.10 (1.8541)

Cylinder Head and Valves

Cylinder Head (Max Out of Flatness), mm (in) ................ 0.05 (0.002)
Valve Clearance (Cold), mm (in) ................ 0.20 (0.008)
Intake Valve Seat Width (Std), mm (in) ................ 1.36-1.53 (0.054-0.060)
Intake Valve Seat Width (Wear Limit), mm (in) ................ 1.98 (0.078)
Exhaust Valve Seat Width (Std), mm (in) ................ 1.66-1.87 (0.065-0.074)
Exhaust Valve Seat Width (Wear Limit), mm (in) ................ 2.27 (0.089)
Intake and Exhaust Valves Faces, mm (in) ................ 0.51 (0.020)
Exhaust Valve Face Angle, deg ................ 45
Intake Valve Face Angle, deg ................ 30
Valve Stem O.D (Std), mm (in) ................ 6.94-6.96 (0.2732-0.2740)
Valve Stem O.D (Wear Limit), mm (in) ................ 6.90 (0.2717)
Valve Guide I.D (Maximum Clearance), mm (in) ................ 0.20 (0.008)
Valve Guide I.D (Std), mm (in) ................ 7.00-7.02 (0.275-0.276)
Valve Guide I.D (Wear Limit), mm (in) ................ 7.08 (0.279)
Valve Springs Free Length, mm (in) ................ 40.00 (1.575)
Exhaust Valve Seat Angle, deg ................ 45
Intake Valve Seat Angle, deg ................ 30
Camshaft End Play, mm (in) ................ 0.05-0.20 (0.0020-0.0079)
Cam Lobe Height, mm (in) ................ 38.635-38.765 (1.521-1.526)
Camshaft Journal O.D (Gear Housing), mm (in) ................ 44.92-44.95 (1.769-1.770)
Camshaft Journal O.D (Flywheel), mm (in) ................ 44.92-44.95 (1.769-1.770)
Camshaft Journal O.D (Intermediate), mm (in) ................ 44.91-44.94 (1.768-1.769)
Camshaft Bushing I.D, mm (in) ................ 44.990-45.055 (1.771-1.744)
Camshaft Bushing Clearance, mm (in) ................ 0.20 (0.0078)
Camshaft Bore I.D, mm (in) ................ 45.00-45.025 (1.772-1.773)
Rocker Arm Shaft O.D (Std), mm (in) ................ 15.97-15.98 (0.6286-0.6293)
Rocker Arm Shaft O.D (Wear Limit), mm (in) ................ 15.95 (0.6280)
Rocker Arm and Shaft Support Clearance, mm (in) ................ 0.13 (0.005)
Rocker Arm and Shaft Support I.D (Std), mm (in) ................ 16.00-16.02 (0.630-0.631)
Rocker Arm and Shaft Support I.D (Wear Limit), mm (in) ................ 16.09 (0.633)

Pistons and Piston Rings

Piston O.D (Std), mm (in) ................ 77.895-77.925 (3.067-3.068)
Piston O.D (Wear Limit), mm (in) ................ 77.81 (3.063)
Piston O.D (0.25 mm Oversize), mm (in) ................ 78.15-78.18 (3.076-3.077)
Piston O.D (0.50 mm Oversize), mm (in) ................ 78.40-78.42 (3.086-3.087)
Piston Pin O.D (Std), mm (in) ................ 22.991-23.00 (0.905-0.906)
Piston Pin O.D (Wear Limit), mm (in) ................ 22.90 (0.902)
Piston Pin Bore Clearance, mm (in) ................ 0.045 (0.0018)
Piston Pin Bore I.D (Std), mm (in) ................ 23.00-23.009 (0.9055-0.9059)
Piston Pin Bore I.D (Wear Limit), mm (in) ................ 23.02 (0.906)
Piston Pin Bushing Clearance, mm (in) ................ 0.110 (0.0043)
Piston Pin Bushing I.D (Std), mm (in) ................ 23.025-23.038 (0.9065-0.9070)
Piston Pin Bushing I.D (Wear Limit), mm (in) ................ 23.10 (0.909)
Top Ring Groove Clearance, mm (in) ................ 0.075-0.105 (0.0030-0.0041)
Second Ring Groove Clearance, mm (in) ................ 0.035-0.070 (0.0014-0.0028)
Oil Ring Groove Clearance, mm (in) ................ 0.030-0.060 (0.0012-0.0024)
Top Ring End Gap, mm (in) ................ 0.20-0.40 (0.008-0.016)
Second Ring End Gap, mm (in) ................ 0.20-0.40 (0.008-0.016)
Oil Ring End Gap, mm (in) ................ 0.20-0.40 (0.008-0.016)

Tightening Torques

Rocker Arm Cover, Nm (lb-ft) ................ 18 (13.3)
Rocker Arm Assembly, Nm (lb-ft) ................ 26 (19.3)
Cylinder Head, Nm (lb-ft) ................ 69 (51)
Exhaust Manifold, Nm (lb-ft) ................ 26 (19.3)
Intake Manifold, Nm (lb-ft) ................ 26 (19.3)
Piston and Connecting Rod, Nm (lb-ft) ................ 39 (29)
Flywheel Housing Screw, Nm (lb-ft) ................ 49 (36)
Crankshaft Rear Oil Seal, Nm (lb-ft) ................ 26 (19.3)
Crankshaft and Main Bearings, Nm (lb-ft) ................ 79 (58)
Flywheel, Nm (lb-ft) ................ 83 (61)
Flywheel Housing, Nm (lb-ft) ................ 49 (36)
Camshaft, Nm (lb-ft) ................ 26 (19.3)
Timing Gear Cover, Nm (lb-ft) ................ 26 (19.3)
Crankcase Housing, Nm (lb-ft) ................ 22 (16.3)
Crankshaft Pulley, Nm (lb-ft) ................ 115 (85)
Oil Pump, Nm (lb-ft) ................ 25 (18)
Thermostat Cover, Nm (lb-ft) ................ 20 (14.8)
Water Pump, Nm (lb-ft) ................ 26 (19.3)
Fan Mounting, Nm (lb-ft) ................ 11 (8.1)
Fuel Injection Pump, Nm (lb-ft) ................ 26 (19.3)
Fuel Injection Nozzles, Nm (lb-ft) ................ 43 (31)