Nissan NA20 Specifications
| Engine Model: Nissan NA20 |
| Engine Type: 4-cycle inline 4-cylinder OHV liquid-cooled gasoline |
| Total Displacement: 121.9 cu.in (1.99 L) |
| Rated Engine Power: 82-100 Hp (61-74 kW) at 5000 rpm |
| Fuel System Type: Single-barrel or twin-barrel carburetor |
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The Nissan NA20 engine is a 2.0-liter,
inline-four, four-stroke, water-cooled gasoline engine developed for use
in Nissan’s commercial vans, trucks, and multipurpose utility vehicles.
As part of the NA-series engine family, the NA20 was engineered with
reliability, longevity, and ease of service as primary objectives. It is
widely recognized for its durability in harsh operating conditions,
including extended idling, heavy stop-and-go driving, and continuous
load cycles typical of commercial environments.
The NA20 features a cast-iron engine block,
cast-iron overhead-valve (OHV) cylinder head, carburetor-based or LPG
fuel systems (depending on version), a mechanical ignition distributor,
and minimal electronic components. Nissan designed the NA20 to operate
with low maintenance costs and stable performance in markets where
service infrastructure may vary.
The NA20 family includes several versions:
- NA20 (standard gasoline variant)
- NA20S (carbureted with emissions adjustments)
- NA20P (LPG version for taxis and commercial fleets)
These versions share core architecture but differ in carburetor
calibration, combustion chamber design, compression ratios, emissions
equipment, and fuel-system components. Regardless of version, the NA20’s
reputation is built upon simplicity, long service intervals, and high
mechanical tolerance under demanding workloads.
The NA20 engine displaces approximately 1,997 cc (121.9 cu in). Bore is
approximately 86.0 mm (3.39 inches), and stroke is approximately 86.0 mm
(3.39 inches), giving it a perfectly square configuration that balances
torque and smoothness across the rpm range.
Compression ratios vary by version:
- NA20: approx. 9.0:1
- NA20S: approx. 8.8:1
- NA20P (LPG): approx. 10.0:1
Maximum power output depends on market and
calibration:
- NA20: approx. 90-100 hp at approx. 4,800-5,200 rpm
- NA20S: approx. 85-95 hp at approx. 4,800-5,200 rpm
- NA20P: approx. 82-90 hp at approx. 4,600-5,000 rpm
Maximum torque:
- Approx. 105-112 lb-ft (142-152 Nm) at approx. 2,400-3,000 rpm
Idle speed is approx. 700-750 rpm. The firing order is 1-3-4-2. Redline
is usually near 5,500 rpm due to OHV valvetrain limitations. The NA20’s
square bore-stroke layout supports smoother operation than the smaller
NA16 and provides improved mid-range torque.
The block is cast iron with thick walls and extended coolant passages
for thermal stability. The crankshaft is forged steel with five main
bearings. Connecting rods are forged steel with precision-machined
bearing surfaces and bushed small ends. Pistons are cast aluminum with
three-ring sets. The rotating assembly is engineered for high
reliability rather than high performance.
The crankshaft journals are machined to tight tolerances to reduce
friction and vibration. The block incorporates main-bearing caps secured
by high-strength bolts to ensure stability under load.
The cylinder head is cast iron with an overhead-valve configuration. The
camshaft is located in the block and operates valves through hardened
pushrods and rocker arms. Each rocker arm includes a screw-and-locknut
adjuster for valve-lash adjustment. The combustion chambers are
wedge-type, supporting consistent fuel-air mixing and reliable ignition.
The intake and exhaust ports are shaped to increase mixture velocity at
low speeds. Valve seats are hardened for durability. The head is highly
resistant to warping when coolant is maintained properly.
The NA20 uses a carburetor-based fuel system in most versions.
Variants include:
- Single-barrel carburetor
- Two-stage progressive carburetor (for improved power and economy)
- Feedback carburetor with oxygen sensor and mixture-control solenoid
(emissions-regulated markets)
Fuel is supplied by a mechanical diaphragm pump delivering approx. 3-5
psi.
Carburetor circuits include:
- Idle circuit
- Main metering circuit
- Secondary throttle circuit (two-barrel versions)
- Accelerator pump
- Automatic or manual choke
The NA20P (LPG version) uses:
- Vaporizer/regulator
- LPG mixer unit
- Solenoid fuel shutoff valve
- Dedicated ignition timing calibration
The lubrication system is a full-pressure wet-sump type.
Specifications:
- Oil capacity: approx. 3.8-4.2 liters (4.0-4.4 US qt)
- Normal oil pressure: approx. 45-55 psi at 3,000 rpm; approx. 10-15 psi
at idle
- Recommended oil: SAE 10W-30 or 10W-40
A crankshaft-driven trochoid oil pump provides pressurized lubrication
to all major components. A full-flow spin-on oil filter captures
contaminants. The valvetrain is lubricated through pushrod passages and
rocker arms.
The cooling system is liquid-cooled with a belt-driven centrifugal water
pump.
System includes:
- Radiator (aluminum-core or copper-brass)
- Thermostat
- Expansion tank
- Heater core
- Engine-driven or electric fan
Specifications:
- Thermostat begins opening: approx. 82°C (180°F)
- Fully open: approx. 95°C (203°F)
- Cooling-system capacity: approx. 6.0-7.0 liters (6.3-7.4 US qt)
- Radiator cap pressure: approx. 13-15 psi
Routine coolant replacement prevents buildup of scale and rust.
| Intake and Exhaust Systems |
The induction system includes:
- Air-cleaner assembly
- Replaceable paper-air filter
- Intake snorkel
- Hot-air valve for cold-start improvement
The intake manifold is cast aluminum or iron depending on market. Runner
length is tuned for improved torque.
The exhaust system employs:
- Cast-iron exhaust manifold
- Single-downpipe configuration
Emissions-equipped variants include:
- EGR valve
- Catalytic converter
- Oxygen sensor (feedback carburetor versions)
The ignition system is mechanical with limited electronic components
depending on production year.
System includes:
- Distributor with centrifugal advance
- Vacuum advance diaphragm
- Single ignition coil
- Optional electronic ignition module (later versions)
- High-tension spark-plug leads
Spark-plug gap typically ranges 0.8-1.0 mm (0.031-0.039 inches). Base
ignition timing is approx. 8-12 degrees BTDC at idle with vacuum
disconnected. Correct timing ensures smooth idle, proper torque, and
controlled emissions.
- Length: 650-700 mm (25.6-27.6 in)
- Width: 550-600 mm (21.6-23.6 in)
- Height: 700-750 mm (27.6-29.5 in)
Dry weight:
- NA20 gasoline: 135-150 kg (298-331 lb)
- NA20P LPG: 140-155 kg (308-342 lb)
Recommended intervals:
- Oil and filter: every 5,000 km (3,000 mi)
- Air filter: every 20,000 km (12,000 mi)
- Fuel filter: every 20,000-30,000 km
- Spark plugs: every 20,000-30,000 km
- Valve-lash adjustment: every major tune-up
- Carburetor cleaning: as required
- Cooling-system flush: every 2 years
Compression pressure:
- Approx. 160-180 psi
- Variation: less than 10 percent
- Cylinder-head bolts: 65-75 lb-ft (88-102 Nm)
- Main-bearing-cap bolts: 55-65 lb-ft (75-88 Nm)
- Connecting-rod bolts: 30-35 lb-ft (40-48 Nm)
- Flywheel bolts: 70-80 lb-ft (95-108 Nm)
- Intake-manifold bolts: 16-18 lb-ft (22-25 Nm)
- Exhaust-manifold nuts: 20-25 lb-ft (27-34 Nm)
- Spark plugs: 13 lb-ft (18 Nm)
- Oil-drain plug: 25-30 lb-ft (34-40 Nm)
The NA20 engine was installed in:
- Nissan Vanette Cargo
- Nissan Caravan (select trims)
- Nissan Atlas (light-duty)
- Nissan trade vans and utility trucks
- Industrial and agricultural equipment
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