Honda B20A Specifications
| Engine Model: Honda B20A |
| Engine Type: 4-cycle inline 4-cylinder DOHC 16-valve liquid-cooled gasoline |
| Total Displacement: 119.5 cu.in (1.96 L) |
| Rated Engine Power: 110-120 Hp (82-89 kW) at 5800 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Honda B20A engine is one of the earliest
members of Honda’s B-series family, predating the more widely known
B16A, B18A, and B18C variants. Introduced in the mid-1980s, the B20A
powered the third-generation Honda Prelude and certain Japanese-market
Accord and Vigor models. While it differs significantly from later
B-series designs-especially in block geometry, mounting angle, and
internal architecture-the B20A was an important evolutionary step that
paved the way for the high-performance DOHC engines Honda developed
throughout the 1990s.
The B20A is a 2.0-liter, inline-four, dual-overhead-cam, 16-valve engine
available in both naturally aspirated and higher-output variants
depending on market and model year. The engine was designed around
Honda’s philosophy of lightweight construction, smooth high-rpm
operation, efficient combustion, and precise machining standards.
Unlike later B-series engines, the B20A
features a forward-leaning block angle and unique bore spacing, making
it incompatible with later B-series components. Nonetheless, it remains
respected for its reliability, strong midrange performance, and smooth
power delivery.
Despite being overshadowed by later VTEC-equipped engines, the B20A
continues to be appreciated by enthusiasts who value its uniqueness,
solid engineering, and link to Honda’s early DOHC performance heritage.
Its rigid block, efficient DOHC head, and well-balanced rotating
assembly make it a durable and capable engine when properly maintained.
The Honda B20A is a four-stroke, inline-four gasoline engine with a
total displacement of 1,958 cc (119.5 cubic inches). Bore is 81.0 mm
(3.19 inches), while stroke is 95.0 mm (3.74 inches), forming an
undersquare configuration optimized for torque development and stable
midrange power output.
Compression ratio varies by variant:
- B20A (base): approx. 9.4:1
- B20A5 (North America, higher output): approx. 9.3:1
- B20A7 (Europe/JDM): approx. 10.5:1
Power output varies significantly depending
on model:
- B20A (standard): approx. 110–120 horsepower (82–89 kW) at 5,500–6,000
rpm
- B20A5: approx. 135 horsepower (101 kW) at 6,000 rpm
- B20A7: approx. 145–150 horsepower (108–112 kW) at 6,100 rpm
Torque output generally ranges between: 110 lb-ft (149 Nm) and 140 lb-ft
(190 Nm) at 4,500–5,000 rpm. Redline is around 6,500–6,800 rpm,
depending on ECU calibration. Idle speed is usually 750 ± 50 rpm. The
firing order is 1-3-4-2.
The block is a cast-iron design with a forward-leaning orientation of
approximately 18–20 degrees. Cylinder liners are cast integrally into
the block. The crankshaft is forged steel and supported by five main
bearings for smooth rotation and durability. Connecting rods are forged
steel with full-floating wrist pins. Pistons are cast aluminum alloy
with friction-reducing coatings.
The aluminum DOHC cylinder head uses a crossflow layout with four valves
per cylinder (16 valves total). Intake valves measure roughly 33 mm
(1.30 in), with exhaust valves measuring about 28 mm (1.10 in). Valve
actuation is achieved through bucket-over-shim mechanical lifters,
requiring periodic manual adjustment. Camshafts are belt-driven, and
timing belt service is essential to long-term reliability.
The combustion chambers use a compact pent-roof design optimized for
efficient swirl and combustion stability. Port shapes emphasize midrange
airflow characteristics while still permitting strong upper-rpm
breathing for the engine’s era.
The fuel system employs Honda’s PGM-FI multi-point electronic fuel
injection system. Fuel is drawn from the tank by an electric in-tank
pump, passed through a fine paper filter, and delivered to a fuel rail
feeding four solenoid-type injectors.
Fuel pressure is regulated at approximately 40–47 psi (275–325 kPa) via
a vacuum-referenced regulator. Excess fuel returns to the tank to
maintain stable pressure across varying loads.
The fuel system incorporates several
essential sensors:
- manifold absolute pressure (MAP) sensor
- throttle position sensor (TPS)
- intake air temperature (IAT) sensor
- oxygen sensor (closed-loop operation)
- engine coolant temperature (ECT) sensor
- crank and cam position sensors located in the distributor
The ECU uses these inputs to manage injector pulse width and maintain
optimal air-fuel ratios. Premium unleaded gasoline with a minimum of 91
RON (87 AKI) is generally adequate, though higher-octane fuel may
improve performance in higher-compression variants such as the B20A7.
The lubrication system is a full-pressure wet-sump type. A trochoid oil
pump mounted on the crankshaft draws oil through a pickup screen, sends
it through a full-flow spin-on filter, and distributes it through
internal galleries to the crankshaft bearings, connecting rod journals,
camshaft journals, and valvetrain components.
Oil capacity is approximately 4.0 liters (4.2 US quarts). Recommended
viscosity is SAE 5W-30 or 10W-30 depending on climate. Normal oil
pressure at high rpm ranges from 50 to 70 psi (345–480 kPa), with idle
pressure remaining above 10 psi (69 kPa).
The PCV (positive crankcase ventilation) system relieves crankcase
pressure and reduces blow-by contamination by routing vapors into the
intake manifold for controlled combustion.
Cooling is provided by a liquid-based, forced-circulation system using a
belt-driven centrifugal water pump. Coolant flows through the block,
cylinder head, radiator, and heater core. Thermostat operation begins
around 82°C (180°F) and is fully open at approximately 95°C (203°F).
System pressure is regulated by a radiator cap rated near 1.1 bar (16
psi). Coolant capacity is roughly 5.5–6.0 liters (5.8–6.3 US quarts). A
50/50 mixture of ethylene glycol and distilled water is recommended.
An electric cooling fan is activated by a thermo-switch in the cooling
system. The ECU monitors coolant temperature for fuel and ignition
corrections.
| Intake and Exhaust Systems |
The intake manifold is an aluminum casting designed to promote strong
midrange torque while still supporting adequate high-rpm breathing. A
throttle body approximately 58–60 mm in size regulates airflow into the
plenum.
The intake system uses a resonated airbox with a dry paper air filter.
Cold-air intake modifications are common among enthusiasts but the OEM
system is efficient and quiet.
The exhaust manifold is a cast-iron design optimized for durability and
consistent exhaust flow. A catalytic converter and tuned exhaust piping
maintain emissions compliance and reduce noise without excessive
backpressure.
| Ignition and Electrical System |
The B20A uses an electronically controlled, distributor-based ignition
system.
The distributor houses:
- ignition coil
- igniter module
- pickup sensor for crank/cam signal generation
Ignition timing is ECU-controlled but base timing may be manually
adjusted by loosening the distributor housing and rotating it slightly.
Spark plug specification commonly includes NGK ZFR6F or equivalent, with
a gap of 1.0–1.1 mm (0.039–0.043 inches).
The ignition system provides stable spark delivery across the operating
range, ensuring efficient combustion and smooth high-rpm operation.
The engine operates on a 12-volt electrical system. Alternator output
ranges between 70 and 80 amperes depending on year. The starter motor is
a reduction-gear design providing consistent cranking torque. Grounds
between block, chassis, and battery terminals must remain clean to
prevent sensor interference.
| VALVE TIMING AND DRIVE MECHANISM |
The timing belt drives both camshafts and the water pump. Replacement
interval is generally 90,000–100,000 km (55,000–62,000 miles). Belt
tension is controlled by a spring-loaded tensioner.
Valve clearance must be checked periodically due to the shim-over-bucket
valvetrain. Proper lash ensures optimal airflow, reduced valvetrain
noise, and maximum power output. Timing marks are located on the crank
pulley and camshaft sprockets for precise belt alignment.
Length: 640 mm (25.2 inches)
Width: 580 mm (22.8 inches)
Height: 670 mm (26.4 inches)
Dry weight is typically 145–155 kg (320–342 lbs), depending on
accessories.
Recommended service intervals include:
Oil and filter changes: 5,000–7,500 km (3,000–4,600 miles)
Air filter: 20,000–30,000 km (12,000–18,000 miles)
Fuel filter: 40,000 km (25,000 miles)
Spark plugs: 20,000–30,000 km (standard), 60,000–80,000 km
(platinum/iridium)
Valve clearance checks: every 40,000–50,000 km
Coolant: every 2 years or 40,000 km
Timing belt: every 90,000–100,000 km
PCV valve: inspect each major service
Compression pressure: typically 170–200 psi (1,170–1,380 kPa) with <10%
variation
Cylinder head bolts (multi-stage
procedure):
Stage 1: 29 Nm (21 lb-ft)
Stage 2: 59 Nm (44 lb-ft)
Stage 3: additional 90°
Stage 4: additional 90°
Main bearing cap bolts: 65–70 Nm (48–52 lb-ft)
Connecting rod bolts: 40–45 Nm (30–33 lb-ft)
Camshaft cap bolts: 10 Nm (7 lb-ft)
Crank pulley bolt: 180–190 Nm (133–140 lb-ft)
Flywheel bolts: 85–95 Nm (63–70 lb-ft)
Spark plugs: 18 Nm (13 lb-ft)
Oil drain plug: 35–40 Nm (26–30 lb-ft)
The B20A engine was used extensively in:
- 1986–1991 Honda Prelude (various trims depending on market)
- Japanese-market Honda Vigor
- Japanese-market Honda Accord variants
- Select regional models requiring a 2.0-liter DOHC engine
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