Mitsubishi 8M22 Specifications
| Engine Model: Mitsubishi 8M22 |
| Engine Type: 4-cycle 8-cylinder V-block OHV 32-valve liquid-cooled diesel |
| Total Displacement: 1161.4 cu.in (19.03 L) |
| Rated Engine Power: 473-542 Hp (353-405 kW) at 2200 rpm |
| Fuel System Type: Direct injection |
____________________________________________________________________________________
The Mitsubishi 8M22 is a 19.0-liter, naturally
aspirated V8 diesel engine belonging to the high-displacement 8M2 series.
Designed for heavy-duty long-haul trucks and large touring buses, the 8M22 was
produced for applications requiring sustained high torque output without the
complexity of forced induction. The engine employs a 90-degree V8 configuration
with overhead valve (OHV) valvetrain operating four valves per cylinder.
The 8M22 achieved its power and torque figures through substantial displacement
rather than turbocharging, a design philosophy that prioritized durability,
serviceability, and thermal stability in demanding commercial applications. The
engine powered Mitsubishi Fuso Super Great trucks and Aero Queen buses across
multiple generations, establishing a reputation for extended service life under
continuous high-load operation.
Engine Type: V8, 4-cycle, water-cooled, naturally aspirated diesel.
Displacement: 19,031 cc (1,161.4 cu.in).
Bore: 142.0 mm (5.59 in).
Stroke: 150.0 mm (5.91 in).
Compression Ratio: 18.5:1.
Valvetrain: Overhead Valve (OHV) with pushrod actuation, 32 valves (4 per
cylinder).
The valvetrain utilizes a single camshaft located within the cylinder block
V-valley.
Valve clearances are adjusted manually using threaded adjusters.
Firing Order: 1-5-7-2-6-3-4-8.
Maximum Power: 473-542 hp (353-405 kW) @ 2,000-2,200 rpm.
Maximum Torque: 1,770-1,960 Nm (1,305-1,445 lb-ft) @ 1,100-1,300 rpm.
The cylinder block is manufactured from high-strength
cast iron with a 90-degree V-angle configuration. Bore diameter measures 142.0
mm (5.59 in). The block features a deep-skirt design extending below the
crankshaft centerline with cross-bolted main bearing caps to provide exceptional
rigidity under sustained high-load operation. Pressed-in cast iron cylinder
liners are replaceable during major overhauls.
The crankshaft is forged steel with eight counterweights, supported by five main
bearings. The block incorporates an integrated oil gallery system feeding the
main bearings, connecting rods, and camshaft bearings. The V-valley houses the
camshaft, fuel injection pump, and associated drive components. Dry weight is
approximately 1,350 kg (2,976 lb).
Valves: 32 total; 16 intake, 16 exhaust.
Intake Valve Diameter: 48.0 mm (1.89 in).
Exhaust Valve Diameter: 44.0 mm (1.73 in).
Valve Stem Diameter: 10.0 mm (0.39 in) for both intake and exhaust.
Valve Seat Inserts: Press-fit inserts; exhaust valve seats are manufactured from
heat-resistant alloy with stellite facing for wear resistance.
Valve Guides: Cast iron guides pressed into the cylinder heads.
Valve Adjustment: Mechanical adjusters with threaded rocker arms and lock nuts.
Valve clearance is set with the engine cold. Intake clearance: 0.40 mm (0.016
in); Exhaust clearance: 0.60 mm (0.024 in). Camshaft: Chilled cast iron camshaft
with induction-hardened lobes, located within the cylinder block V-valley. The
camshaft is driven by gears from the crankshaft. Pushrods transfer motion to
rocker arms mounted on individual pedestals on each cylinder head.
Combustion Chamber: Direct injection configuration with a shallow bowl in the
piston crown. Fuel is injected directly into the combustion chamber, eliminating
the thermal losses associated with indirect injection systems.
The fuel system employs a mechanical in-line injection
pump with direct injection into the combustion chamber. Injection Pump Type:
Bosch or Zexel mechanical in-line pump with an integral mechanical governor. The
pump is driven by gears from the camshaft or crankshaft. Injectors: Mechanical
multi-hole injectors with an opening pressure of 200-250 bar (2,900-3,625 psi)
depending on calibration. Injectors are connected to the injection pump by
individual high-pressure steel lines.
Fuel Filtration: Dual-stage fuel filtration system comprising a primary filter
with water separator and a secondary fine filter. A manual priming pump is
incorporated for system bleeding. Fuel Pressure: Injector opening pressure
ranges from 200-250 bar (2,900-3,625 psi). A gear-type fuel feed pump supplies
fuel from the tank to the injection pump.
Governor: Mechanical centrifugal governor controlling idle speed and maximum
engine speed. The governor incorporates a variable-speed control for road speed
governing in vehicle applications. Cold Start Device: Manual or automatic cold
start advance mechanism adjusting injection timing for cold engine operation.
The lubrication system is a full-flow, pressurized
design utilizing a gear-type oil pump driven by the crankshaft. Oil Pump Type:
Gear-type pump mounted to the front of the crankshaft within the timing gear
housing. Oil Capacity: 28-35 liters (29.6-37.0 qt) including oil filter
replacement. Capacity varies with sump configuration, which differs between
truck and bus installations. Recommended Oil Viscosity: 15W-40 or 20W-50.
Oil Quality Requirement: API CF, CF-4, CG-4, or later heavy-duty diesel
classifications. Oil Pressure: At warm idle, pressure ranges from 1.0-2.0 bar
(14-29 psi). At rated speed (2,000 rpm), pressure reaches 4.0-5.0 bar (58-73
psi). Oil Cooler: Large-capacity liquid-to-oil plate-type heat exchanger mounted
on the cylinder block, utilizing engine coolant for thermal stabilization.
Oil Filter: Full-flow spin-on or cartridge-type filters in a dual configuration
for increased filtration capacity and redundancy. Bypass valves maintain oil
flow if filter elements become restricted. Oil Jets: Piston cooling jets (oil
squirters) direct lubricant to the underside of each piston crown for thermal
management under sustained high-load operation. Crankcase Ventilation: Closed
system with an integrated oil separator, routing blow-by gases to the engine
intake system.
The cooling system is pressurized and utilizes a
centrifugal water pump driven by the crankshaft through gear drive or accessory
belt depending on installation. Water Pump Type: Centrifugal pump with a cast
iron housing and cast impeller, designed for high-flow capacity. Thermostat:
Dual wax-pellet thermostats located in the coolant outlet housing to manage the
large coolant flow requirements. Opening temperature is 76-82 °C (169-180 °F).
Coolant Capacity: 40-50 liters (42.3-52.8 qt) inclusive of engine block,
cylinder heads, radiator, and heater circuits. Capacity varies with chassis
configuration. Radiator: Heavy-duty cross-flow aluminum or copper-brass core
with a large frontal area. Cooling fan configuration consists of an
engine-driven mechanical fan with a viscous clutch, sized to maintain operating
temperatures under maximum load at low vehicle speeds.
System Pressure: Radiator cap rated at 0.9-1.1 bar (13-16 psi). Coolant
Specification: Ethylene glycol-based coolant with corrosion inhibitors suitable
for cast iron engine construction and aluminum radiator components.
Timing System: Gear-driven timing system with
precision-ground gears transferring drive from the crankshaft to the camshaft,
fuel injection pump, and accessory drives. No belts or chains are utilized for
timing functions, contributing to extended service intervals and reliability.
Exhaust System: Cast iron exhaust manifolds per cylinder bank merging into a
single exhaust outlet. Emissions equipment varies by market and production year;
later variants incorporate a Diesel Oxidation Catalyst (DOC) and, on certain
applications, a Diesel Particulate Filter (DPF).
Intake Manifold: Cast iron manifold with individual runners per cylinder,
designed to provide uniform air distribution across all eight cylinders. The
manifold incorporates an intake air heater for cold-start assistance in
low-temperature conditions.
Air Intake System: Heavy-duty air cleaner with a replaceable paper element,
sized for the engine’s air consumption at rated power. A restriction indicator
provides maintenance notification when element replacement is required.
Starting System: 24-volt electric starter with a heavy-duty solenoid, utilizing
two 12-volt batteries connected in series. The starter motor is gear-reduction
type to provide sufficient cranking torque for the large displacement engine.
Glow Plugs: Not equipped on direct injection diesel engines of this class. Cold
starting is aided by the intake air heater and high-compression ratio.
Engine Mounting: Four-point elastomeric mounting system with heavy-duty
isolators designed to absorb vibration while maintaining alignment with the
transmission.
Overall Length: 1,350 mm (53.1 in) measured from
accessory drive pulley face to flywheel housing mounting flange.
Overall Width: 1,100 mm (43.3 in) inclusive of exhaust manifolds and intake
system.
Overall Height: 1,250 mm (49.2 in) from oil pan bottom surface to valve cover
top surface.
Dry Weight: 1,340-1,360 kg (2,954-2,998 lb) depending on accessory drive
components and sump configuration.
Valve Clearance (cold): Intake 0.40 mm (0.016 in);
Exhaust 0.60 mm (0.024 in). Adjustment interval is 40,000 km (25,000 miles) for
heavy-duty applications. Timing Gear Inspection Interval: Gear backlash and wear
inspection recommended at 200,000 km (124,000 miles). No replacement interval is
specified under normal operating conditions. Coolant Change Interval: 80,000 km
(50,000 miles) or 2 years.
Injection Pump Timing: Static injection timing set to manufacturer
specifications per injection pump model. Timing is adjusted by shim selection on
the pump mounting flange. Injector Opening Pressure: 200-250 bar (2,900-3,625
psi). Inspection interval is 40,000 km (25,000 miles). Drive Belt Tension
(Accessory): 15-20 mm (0.59-0.79 in) deflection under 15 kg (33 lb) of force at
the midpoint of the longest span on belt-driven accessory systems.
Engine Oil Change Interval: 15,000-20,000 km (9,300-12,400 miles) depending on
operating conditions and oil analysis results. Idle Speed (warm, neutral):
550-600 rpm. Fuel Filter Change Interval: 20,000 km (12,500 miles) or as
indicated by water-in-fuel sensor and restriction gauge. Compression Pressure:
Minimum specification per cylinder is 2.8 MPa (406 psi) with maximum variation
between cylinders of 0.3 MPa (44 psi).
Cylinder Head Bolts (cold): Step 1: 100 Nm (74 lb-ft).
Cylinder Head Bolts (cold): Step 2: 200 Nm (148 lb-ft).
Crankshaft Damper Pulley Bolt: 500-550 Nm (369-406 lb-ft).
Connecting Rod Cap Bolts: 180-200 Nm (133-148 lb-ft).
Main Bearing Cap Bolts: 250-280 Nm (184-207 lb-ft).
Main Bearing Cross bolts: 100-120 Nm (74-89 lb-ft).
Camshaft Bearing Cap Bolts: 80-90 Nm (59-66 lb-ft).
Camshaft Drive Gear Bolts: 180-200 Nm (133-148 lb-ft).
Valve Cover Bolts: 20-25 Nm (15-18 lb-ft).
Rocker Arm Shaft Bolts: 80-90 Nm (59-66 lb-ft).
Intake Manifold Nuts: 40-45 Nm (30-33 lb-ft).
Exhaust Manifold Nuts: 50-60 Nm (37-44 lb-ft).
Oil Pan Bolts: 25-30 Nm (18-22 lb-ft).
Oil Pump Mounting Bolts: 40-45 Nm (30-33 lb-ft).
Water Pump Bolts: 40-45 Nm (30-33 lb-ft).
Injection Pump Mounting Nuts: 40-45 Nm (30-33 lb-ft).
Injection Line Fittings: 30-35 Nm (22-26 lb-ft).
Injector Hold-Down Clamps: 80-90 Nm (59-66 lb-ft).
Flywheel / Drive Plate Bolts: 250-280 Nm (184-207 lb-ft).
Engine Mount Bracket Bolts: 120-140 Nm (89-103 lb-ft).
Mitsubishi Fuso Super Great (FP, FV, FS series):
1980s-2000s. The 8M22 powered heavy-duty truck configurations including tractor
heads, rigid chassis, and dump truck variants. Applications included long-haul
freight, construction, and heavy transport operations.
Mitsubishi Fuso Aero Queen: 1980s-2000s. The 8M22 was installed in the Aero
Queen touring bus series, providing the torque required for sustained highway
operation with full passenger loads and luggage capacity.
Mitsubishi Fuso Aero King (Double Decker): 1980s-1990s. The 8M22 served as the
powertrain for the Aero King double-decker bus, where the engine’s high torque
output was essential for the elevated gross vehicle weight of the configuration.
Specialty Heavy-Duty Vehicles: The 8M22 was utilized in specialized applications
including fire apparatus, heavy recovery vehicles, and industrial equipment
where the naturally aspirated design provided simplicity and reliability in
demanding operational environments.
____________________________________________________________________________________
| Car Engines Technical Specifications |
| Small Engines Technical Specifications |
| Industrial Engines Technical Specifications |
| Outboard Engines Technical Specifications |
