Yanmar 2V78 Specifications
| Engine Model: Yanmar 2V78 |
| Engine Type: 4-stroke 2-cylinder V-twin water-cooled diesel |
| Total Displacement: 45.7 cu.in (0.75 L) |
| Rated Engine Power: 20 Hp (14.9 kW) at 3600 rpm |
| Fuel System Type: Indirect injection |
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The Yanmar 2V78 is a compact, liquid-cooled
V-twin diesel engine from the "Vengeance" series, introduced to the
North American market in 1997 as an alternative to gasoline engines in
commercial turf equipment. This engine features an 80-degree V-angle
with a vertical shaft configuration, primarily designed for zero-turn
mowers, small tractors, welders, generators, chippers, and industrial
equipment.
The Yanmar 2V78 utilizes indirect injection with an all-new spherical
combustion chamber design, optimized through computer modeling to
achieve complete combustion and reduced emissions. The liberal use of
aluminum in the engine block, gear case, and cylinder head contributes
to a dry weight of only 56 kg (123 lb), targeting gasoline engine
dimensions for tight equipment spaces. The engine meets all current CARB
and proposed EPA requirements from its launch period.
Engine Type: 4-cycle, water-cooled, 80° V-twin diesel
Number of Cylinders: 2
Displacement: 0.749 L (45.7 cu.in)
Bore x Stroke: 78 mm x 78.4 mm (3.07 in x 3.09 in)
Compression Ratio: 23:1
Combustion System: Indirect injection (IDI) with spherical chamber
design
Aspiration: Natural (atmospheric)
Cooling System: Liquid-cooled with radiator and centrifugal pump
Maximum Output: 14.9 kW (20 hp) at 3600 rpm
Fast Idle Speed: 3200-3300 rpm
Slow Idle Speed: 1400-1500 rpm
Max Power: 16.1 hp (12 kW) at 2800
Max Power: 17.2 hp (12.7 kW) at 3000 rpm
Max Power: 18.1 hp (13.4 kW) at 3200 rpm
Max Power: 19 hp (14 kW) at 3400 rpm
Starting System: Electric start, 12V with 1.0 kW starter
Rotation Direction: Counter-clockwise viewed from flywheel side
Fuel Injection Pressure: 11.8 MPa (120 kg/cm2)
The cylinder block is manufactured from die-cast aluminum, a material
choice that directly contributes to the engine's reduced weight of 115
lb without muffler. The open deck design of the block provides more
effective cooling and reduced emissions, while a new metal gasket
improves sealing. The gear case is also die-cast aluminum, integrating
with the block structure.
The engine uses an 80-degree V-angle configuration between the two
cylinders. The liberal use of aluminum extends to major engine
structures, with a 30 percent reduction in reciprocating weight achieved
through aluminum pistons. The block houses the combined fuel injection
pump and governor mechanism within the engine block.
The cylinder head is squeeze-cast aluminum, positioned as individual
heads or a single casting covering both cylinders. The valve arrangement
uses two valves per cylinder, one intake and one exhaust, actuated by a
pushrod and rocker arm system from a camshaft located within the block.
The combustion chamber features an all-new spherical design, which,
combined with a flat crown aluminum piston and higher piston top ring,
results in less dead space in the cylinder and more complete combustion.
The glow plug has been relocated to between the cylinder banks for
improved cold starting. The valve clearance specification when cold is
0.2 mm (0.008 in) for both intake and exhaust valves. The compression
pressure specification is 2.94 MPa (30 kg/cm2) at 250 rpm of cranking
speed.
The fuel system is a mechanical indirect injection system with the fuel
injection pump and injector nozzles built in-house by Yanmar. The pump
and governor mechanism are combined in a single unit and housed within
the engine block, reducing external components and potential leak
points.
A solenoid-operated fuel feed pump and air bleed system are standard
equipment, simplifying fuel system priming. The injection timing is set
to 15 to 17 degrees before top dead center (TDC). The fuel filter is a
paper element type. Fuel injection pressure is set to 11.8 MPa (120
kg/cm2). The governor mechanism is mechanical, designed to maintain
stable engine speeds under varying loads.
The lubrication system is a forced lubrication system using a
trochoid-type oil pump, a design chosen for its compactness and reliable
oil delivery. The oil filter is a spin-on, full-flow cartridge type. The
system uses a replaceable full-flow oil filter as standard equipment.
The total engine oil capacity is 2.3 L (2.4 qt) including the filter.
A lube oil pressure switch is a standard feature, providing warning of
low oil pressure. The recommended oil grade is selected based on ambient
operating temperature. Forced lubrication ensures positive oil delivery
to all critical moving components, including the crankshaft bearings,
connecting rod bearings, and camshaft.
The cooling system is a liquid-cooled, pressurized system with a
centrifugal water pump. A cooling fan is mounted on the flywheel or
crankshaft to draw air through the radiator. The radiator is positioned
above the engine on vertical shaft applications, with the cooling fan
forcing air downward through the radiator core. A thermostat is
incorporated into the system to regulate coolant temperature,
maintaining optimal operating conditions.
A water temperature switch is standard, providing warning of
overheating. The system uses a radiator and a separate sub tank
(recovery tank) available as an option. The engine meets CARB and EPA
emissions requirements through effective thermal management and
combustion chamber design.
| Intake and Exhaust Systems |
Air Intake System: A dry-type paper air cleaner with primary and
secondary elements is used. The air cleaner is available as an optional
component from Yanmar, along with the muffler.
Exhaust System: The muffler is available as an option from Yanmar. When
packaged with the Yanmar-sourced muffler, the engine weight increases to
56 kg (123 lb).
A 12-volt system is standard, using a 1.0 kW starter motor and a 20-amp
dynamo (alternator). An air intake pipe with resonator is standard to
reduce induction noise. A stop solenoid provides electrical engine
shutdown.
Timing Drive: The engine uses composite gears in the gear train, which
has been lightened to reduce rotating mass and vibration. The gear train
drives the camshaft, fuel injection pump, and balance shafts.
Balance System: The engine is designed with reduced moving and static
engine weight, yielding noise and vibration levels more reminiscent of a
three-cylinder engine than a conventional twin.
Dry Weight (without muffler): 52 kg (115 lb)
Dry Weight (with muffler): 56 kg (123 lb)
Length: 468 mm (18.4 in)
Width: 396 mm (15.6 in)
Height: 447 mm (17.6 in)
Engine Oil Capacity (with filter): 2.3 L (2.4 qt)
Recommended Oil Grade: Diesel engine oil meeting API CD/CF
classification
Oil Change Interval: Every 100 operating hours (initial change at 50
hours)
Oil Filter Replacement: Replace with every oil change
Fuel Filter Replacement: Every 200 operating hours or 6 months
Valve Clearance (Cold): Intake: 0.2 mm (0.008 in); Exhaust: 0.2 mm
(0.008 in)
Valve Adjustment Interval: Every 500 operating hours
Injection Timing: 15 to 17 degrees before TDC
Injection Pressure: 11.8 MPa (120 kg/cm2)
Compression Pressure: 2.94 MPa (30 kg/cm2) at 250 rpm
Air Cleaner Service: When restriction indicator shows vacuum or every
100 hours
Cooling System: Check coolant level daily; replace every 1,000 hours or
2 years
Cylinder Head Bolts: 50 to 55 Nm (37 to 41 lb-ft)
Connecting Rod Cap Bolts: 25 to 30 Nm (18 to 22 lb-ft)
Main Bearing Cap Bolts: 60 to 65 Nm (44 to 48 lb-ft)
Flywheel Bolts: 40 to 45 Nm (30 to 33 lb-ft)
Injector Nozzle Holder Nuts: 25 Nm (18 lb-ft)
Rocker Arm Shaft Bracket Bolts: 20 Nm (15 lb-ft)
Oil Pan Drain Plug: 35 Nm (26 lb-ft)
Intake Manifold Bolts: 22 Nm (16 lb-ft)
Exhaust Manifold Nuts: 25 Nm (18 lb-ft)
Turf Equipment: John Deere F735, GX355, and GX355D front-mount mowers;
Exmark zero-turn mowers; Countax D18 and D50 garden tractors.
Industrial Equipment: Small construction equipment; welders; chippers;
sweepers.
Power Generation: Portable generator sets.
Utility Vehicles: All-terrain vehicles (ATVs) and small utility
vehicles.
Marine: Small marine auxiliary applications.
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