Kubota D782-E

Kubota D782-EThe Kubota D782-E is a 0.78 L (778 cc, 47.5 cu·in) straight-three, water-cooled naturally aspirated diesel engine manufactured by Kubota.

The Kubota D782-E engine has a spherical type сombustion сhamber with glow plug, Bosch MD mini fuel injection pump, and Bosch throttle type injection nozzle.

The compression ratio rating is 24.0:1. Cylinder bore is 67.0 mm (2.64 in) and the piston stroke is 73.6 mm (2.9 in).

The D782-E diesel engine produced 18.4 PS (13.5 KW; 18.1 HP) at 3,200 rpm of net (intermittent) horsepower and 15.9 PS (11.7 KW; 15.7 HP) at 3,200 rpm of net (continuous) horsepower.

The breakdown of the engine code is as follows:

  • D – 3-cylinders
  • 78 – Approximate displacement 780 cc
  • 2 – Super-Mini series
  • E – EPA/CARB Tier 1 level

General information

Engine Specifications
Engine code D782-E
Layout Straight-3, vertical diesel engine
Fuel type Diesel fuel No.2-D
Production
Displacement 0.78 L, 778 cm3 (47.5 cu in)
Max. Horsepower Net (intermittent): 18.4 PS (13.5 KW; 18.1 HP) at 3,200 rpm
Net (continuous): 15.9 PS (11.7 KW; 15.7 HP) at 3,200 rpm
Torque output
Injection type Indirect injection
Cooling system Liquid-cooled
Fuel injection pump Bosch MD type mini fuel injection pump
Fuel nozzle Bosch throttle type
Starting system Electric starting with 12V (0.8 kW) starter
Starting support device Glow plug in combustion chamber
Governor Centrifugal ball mechanical governor
Power adder None
Firing order 1-2-3
Dimensions (L x W x H): 426 x 398 x 519 mm (16.8 x 15.7 x 20.4 in)
Weight 63.5 kg (140.0 lbs)

Cylinder block

Cylinder block
Compression ratio: 24.0:1
Cylinder bore: 67.0 mm (2.64 in)
Piston stroke: 73.6 mm (2.9 in)
Number of piston rings (compression / oil): 2 / 1
Cylinder inner diameter: 67.000-67.019 mm (2.6378-2.6385 in)
Piston skirt diameter
Piston ring side clearance: Second 0.085-0.112 mm (0.0033-0.0044 in)
Oil 0.020-0.060 mm (0.0008-0.0024 in)
Piston ring end gap: Top 0.150-0.300 mm (0.0059-0.0118 in)
Second 0.300-0.450 mm (0.0118-0.0177 in)
Oil 0.150-0.300 mm (0.0059-0.0118 in)
Piston pin outer diameter 20.002-20.011 mm (0.7875-0.7878 in)
Crankshaft main journal diameter: Flywheel side: 43.934-43.950 mm (1.72969-1.73032 in)
Other: 39.934-39.950 mm (1.5722-1.5728 in)
Crankpin diameter: 33.959-33.975 mm (1.337-1.3376 in)

Cylinder head

Cylinder head
Valve Arrangement: OHV, gear drive
Valves: 6 (2 valves per cylinder)
Valve timing: INTAKE
EXHAUST
Valve seat width: INTAKE 2.120 mm (0.0835 in)
EXHAUST 2.120 mm (0.0835 in)
Valve stem diameter: INTAKE 5.968-5.980 mm (0.2349-0.2354 in)
EXHAUST 5.968-5.980 mm (0.2349-0.2354 in)
Valve spring free length: INTAKE 31.6 mm (1.2441 in)
EXHAUST 31.6 mm (1.2441 in)
Camshaft lobe height: INTAKE 26.88 mm (1.0583 in)
EXHAUST 26.88 mm (1.0583 in)
Camshaft journal diameter: 32.934-32.950 mm (1.2966-1.2972 in)

Tightening torque

Tightening torque specs
Head cover cap nuts (M6x1.0): 3.9-5.3 Nm (0.4-0.6 kgf-m, 2.9-4.3 lb-ft)
Head bolts (M8x1.25): 39.2-44.1 Nm (4.0-4.5 kgf-m, 28.9-32.5 lb-ft)
Main bearing case bolts 1 (M6x1.0): 12.7-15.7 Nm (1.3-1.6 kgf-m, 9.4-11.6 lb-ft)
Main bearing case screw 2 (M7x1.0): 26.5-30.4 Nm (2.7-3.1 kgf-m, 19.5-22.4 lb-ft)
Flywheel bolts (M10x1.25): 53.9-58.8 Nm (5.5-6.0 kgf-m, 39.8-43.4 lb-ft)
Connecting rod bolts (M7x0.75): 26.5-30.4 Nm (2.7-3.1 kgf-m, 19.5-22.4 lb-ft)
Rocker arm bracket nuts (M6x1.0): 9.81-11.28 Nm (1.0-1.15 kgf-m, 7.23-8.32 lb-ft)
Idle gear shaft bolts (M6x1.0): 9.8-11.3 Nm (1.00-1.15 kgf-m, 7.2-8.3 lb-ft)
Idle gear shaft screws (M6x1.0): 9.8-11.3 Nm (1.00-1.15 kgf-m, 7.2-8.3 lb-ft)
Glow plugs (M8x1.0): 7.8-14.7 Nm (0.8-1.5 kgf-m, 5.8-10.8 lb-ft)
Nozzle holder assembly (M20x1.5): 49.0-68.6 Nm (5.0-7.0 kgf-m, 36.2-50.6 lb-ft)
Nozzle holder and nozzle retaining nut: 58.8-78.5 Nm (6.0-8.0 kgf-m, 43.4-57.9 lb-ft)
Injection pipe retaining nuts: 24.5-34.3 Nm (2.5-3.5 kgf-m, 18.1-25.3 lb-ft)

Maintenance data

Valve clearance
Intake valve 0.145-0.185 mm (0.0057-0.0073 in)
Exhaust valve 0.145-0.185 mm (0.0057-0.0073 in)
Compression pressure
Standard 2.84-3.24 MPa, 29-33 kgf/cm2, 412-469 psi
Oil system
Recommended engine oil CD or CE
SAE Viscosity Number SAE 10W-30, 10W-40
Engine oil capacity 3.6 L (3.8 US. qt, 3.17 Imp. qt.)
Fuel system
Injection timing: 20°
Fuel injection pressure 13.73-14.71 MPa (140-150 kgf/cm2, 1991-2133 psi)
Cooling system
Coolant capacity 3.1 liters (3.3 US.qts, 2.7 Imp. qts)
Thermostat’s valve opening temperature: 69.5-72.5°C (157.1-162.5°F)
Temperature at which thermostat completely opens: 85°C (185°F)
Electrical system
Battery: 12V, 35Ah or equivalent
Starter mica undercut: 0.5-0.8 mm (0.0197-0.0315 in)
Starter brush length: 16.0 mm (0.6299 in)
Alternator (no-load voltage): AC 20V at 5,200 rpm
Glow plug resistance: Approx 0.9 Ω
Alternator stator resistance: Less than 1.0 Ω
Alternator rotor resistance: Less than 2.9 Ω
Alternator slip ring: 14.4 mm (0.567 in)
Alternator brush Length: 10.5 mm (0.413 in)
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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3 Comments

  1. Kubota rates this engine at 17 hp sometimes and 21hp at other times …. So what is true ?? IN there GR2120 lawn tractor ???

    • On my ZD-21 ZTR mower the difference is due to the governed RPM. The ZD-21 engine is governed to run at 3200 RPM. At this speed, it produces about 18 HP. But Kubota labels the mower a ZD-21 because 1) that is the engine power when governed at 3600 RPM. A bit of a scam, but not one that bothers me. The ZD-21 title simply sounds a bit better and might help sell what is already a truly excellent mower. I’ve had mine for going on 24 years now and the little engine has never needed repairs–not even a glow plug. It is usually run wide open. Truly amazing.

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