Honda G20A Specifications
| Engine Model: Honda G20A |
| Engine Type: 4-cycle inline 5-cylinder SOHC 20-valve liquid-cooled gasoline |
| Total Displacement: 121.8 cu.in (1.99 L) |
| Rated Engine Power: 153-163 Hp (114-118 kW) at 6700 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Honda G20A represents a distinct engineering
chapter for Honda, positioned as a premium powerplant for luxury sedans such as
the Honda Inspire and Vigor. Its slanted inline-five architecture inherently
provides better primary and secondary balance than a four-cylinder engine,
contributing to a high degree of operational smoothness and a distinctive
exhaust note. The engine employs a single overhead camshaft (SOHC) operating 20
valves via rocker arms, a design chosen to reduce mechanical complexity while
maintaining high volumetric efficiency.
The use of an aluminum cylinder block with cast iron liners reduced overall
mass, aiding vehicle dynamics. The G20A delivered a broad torque curve suitable
for sedate cruising, with a sharp power increase at higher engine speeds,
culminating in a 6,800 rpm redline. It remained in production for nearly a
decade, undergoing incremental refinements to emissions control and power output
before its discontinuation.
Engine Type: 5-cylinder, inline, naturally aspirated, 4-stroke, gasoline.
Engine Code: Honda G20A.
Configuration: Longitudinal, slanted (20 degrees from vertical) front-engine,
front-wheel drive.
Displacement: 1,996 cc (121.8 cu.in).
Bore: 82.0 mm (3.228 in).
Stroke: 75.6 mm (2.976 in).
Bore/Stroke Ratio: 1.08:1 (oversquare).
Compression Ratio: 9.3:1 to 9.7:1 depending on model year and emissions
specifications.
Early variants utilized 9.3:1, while later iterations increased to 9.7:1.
Valvetrain: SOHC (Single Overhead Camshaft), 4 valves per cylinder, 20 valves
total.
Valve actuation via belt-driven camshaft, rocker arms, and hydraulic lash
adjusters.
Fuel System: Honda PGM-FI (Programmed Fuel Injection), multi-point, sequential
fuel injection.
Ignition System: Fully electronic, distributor-type with integrated ignition
coil.
Firing Order: 1-2-4-5-3.
Power Output: 114-118 kW (153-163 hp) at 6,700 rpm.
Torque Output: 186.3 Nm (19.0 kgfm / 137 lb-ft) at 4,000 rpm.
Maximum Engine Speed: 6,800 rpm (redline)
Engine Oil Capacity: 5.2 liters (5.5 US qt) including oil filter.
The cylinder block is constructed from cast aluminum
alloy to reduce overall engine mass. Cast iron cylinder liners are permanently
cast into the block to provide a durable, low-friction surface for the piston
rings. The block features an open-deck design, where the cylinders are not fully
enclosed by the block’s upper structure, which enhances cooling efficiency
around the bore centers.
The longitudinal mounting orientation dictated a unique engine mount
configuration and a slanted axis to lower the vehicle’s center of gravity. The
crankcase is of a skirted design, providing rigidity for the main bearing caps,
which are secured with four bolts each. The block incorporates a rear-mounted
oil filter housing and a water jacket designed for uniform thermal distribution
across all five cylinders.
The cylinder head is a cast aluminum cross-flow design,
with the intake manifold positioned on the engine’s right side and the exhaust
manifold on the left. The SOHC configuration uses a single camshaft driven by a
toothed timing belt. The camshaft actuates 20 valves through a system of rocker
arms.
Each rocker arm incorporates a hydraulic lash adjuster (HLA), which maintains
zero valve clearance automatically, eliminating the need for periodic valve
adjustments. The four valves per cylinder are arranged in a pent-roof combustion
chamber. Intake valves are larger in diameter than the exhaust valves to
optimize volumetric efficiency. The valve seats are manufactured from a sintered
alloy to withstand high combustion temperatures and provide longevity.
The engine utilizes the Honda PGM-FI system, a
multi-point electronic fuel injection. A high-pressure electric fuel pump,
located within the fuel tank, supplies fuel to a set of injectors mounted
directly in the intake manifold runners, one per cylinder. Fuel delivery is
sequential, meaning each injector fires once per engine cycle in time with its
cylinder’s intake stroke.
The system is managed by an Electronic Control Unit (ECU) that receives inputs
from sensors including a mass airflow sensor, throttle position sensor, engine
coolant temperature sensor, crankshaft position sensor, and oxygen sensor. The
ECU calculates the precise fuel injection duration and ignition timing to
maintain a stoichiometric air-fuel ratio for optimal combustion efficiency and
emission control.
The lubrication system is a fully pressurized, wet-sump
type. A gear-type oil pump, driven directly by the crankshaft, draws oil from a
baffled aluminum oil pan. The pump delivers oil through a full-flow, spin-on
canister filter located on the rear of the cylinder block. From the filter, oil
is routed through a main oil gallery to supply the crankshaft main bearings,
connecting rod bearings, and camshaft bearings.
A dedicated oil circuit feeds the hydraulic lash adjusters in the cylinder head
via passages through the rocker shaft assembly. An oil pressure switch mounted
on the block signals the ECU and activates a warning light if pressure falls
below a specified threshold.
The cooling system is a pressurized, thermosiphon-type
system with a water pump driven by the timing belt. Coolant circulation begins
with a centrifugal water pump that forces coolant through the cylinder block’s
water jacket, around the cylinder liners and into the cylinder head. The
cross-flow radiator is mounted ahead of the engine.
A wax-type thermostat, located in a housing at the water pump inlet, regulates
coolant flow to maintain an operating temperature of approximately 82°C to 88°C
(180°F to 190°F). An electric cooling fan, controlled by the ECU via a coolant
temperature sensor, provides additional airflow through the radiator during
low-speed operation or idle conditions. A separate expansion tank allows for
coolant recovery and maintains system pressure through a pressure-rated radiator
cap.
| Intake and Exhaust Systems |
Intake System: A cast aluminum intake manifold features
long, tuned runners to enhance low- to mid-range torque production. The throttle
body is a single, cable-actuated butterfly valve with an integrated idle air
control (IAC) valve to manage idle speed under varying engine loads.
Exhaust System: A stainless steel exhaust manifold collects gases from five
cylinders into a single downpipe. The system includes a primary catalytic
converter located near the manifold for rapid light-off and a secondary
underfloor converter. An oxygen sensor (O2 sensor) is positioned before the
primary converter to provide feedback for closed-loop fuel control.
The system employs a distributor driven by the exhaust
camshaft (in relation to the belt-driven cam). The distributor houses a
crankshaft position sensor (CYP) and a camshaft position sensor (TDC) for ECU
synchronization. Spark timing is controlled entirely by the ECU, which adjusts
the advance curve based on engine load, speed, and coolant temperature. Spark
plugs are resistor-type.
Overall Length: 695 mm (27.4 in)
Overall Width: 615 mm (24.2 in)
Overall Height: 680 mm (26.8 in) measured from the crankshaft centerline to the
top of the intake manifold.
Dry Weight: 165 kg (364 lb), inclusive of intake and exhaust manifolds but
exclusive of transmission and ancillary components such as the alternator and
power steering pump.
Engine Oil: Viscosity 5W-30 or 10W-30, API SG or
higher. Capacity with filter: 5.2 liters (5.5 qt). Coolant: Ethylene
glycol-based, phosphate-free. Capacity: 7.1 liters (7.5 qt). Timing Belt:
Replacement interval of 96,000 km (60,000 mi). Interference engine design;
failure results in valve-to-piston contact.
Spark Plugs: NGK PFR6G-11 or equivalent. Electrode gap: 1.0-1.1 mm (0.039-0.043
in). Replacement interval: 48,000 km (30,000 mi). Fuel Filter: Replacement
interval of 48,000 km (30,000 mi). Idle Speed: 700 ± 50 rpm in neutral or park,
with all accessories off. Ignition Timing: 15° ± 2° BTDC at idle speed with
service check connector shorted.
Cylinder Head Bolts: Step 1: 29 Nm (21 lb-ft).
Cylinder Head Bolts: Step 2: 69 Nm (51 lb-ft).
Connecting Rod Cap Bolts: 35 Nm (26 lb-ft) + 60° turn.
Main Bearing Cap Bolts: 54 Nm (40 lb-ft) + 90° turn.
Camshaft Bearing Cap Bolts: 22 Nm (16 lb-ft).
Rocker Arm Assembly Bolts: 25 Nm (18 lb-ft).
Intake Manifold Nuts and Bolts: 23 Nm (17 lb-ft).
Exhaust Manifold Nuts: 24 Nm (18 lb-ft).
Crankshaft Pulley Bolt: 245 Nm (181 lb-ft).
Flywheel/Flexplate Bolts: 74 Nm (55 lb-ft).
Spark Plugs: 18 Nm (13 lb-ft).
Oil Drain Plug: 39 Nm (29 lb-ft).
The Honda G20A engine was exclusively designated for
Japanese Domestic Market (JDM) vehicles, serving as the sole powerplant for the
2.0-liter variant across several model lines. Its longitudinal orientation was a
defining characteristic of these platforms.
1989-1991: Honda Accord Inspire (CB5) and Honda Vigor (CB5). This
first-generation application featured the initial specification with a 9.3:1
compression ratio.
1992-1994: Honda Inspire (CC3) and Honda Vigor (CC3). These models represented
the second-generation platform, utilizing an updated version of the G20A with
refined emissions controls.
1993-1997: Honda Ascot (CE4) and Honda Rafaga (CE4). These sedans shared the
G20A engine and longitudinal front-wheel-drive architecture.
1995-1997: Honda Inspire (UA1) and Honda Saber (UA1). The final iteration of the
G20A appeared in these models, incorporating the higher 9.7:1 compression ratio
and revised engine management for improved power output before the engine’s
discontinuation.
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