Honda L12B Specifications
| Engine Model: Honda L12B |
| Engine Type: 4-cycle inline 4-cylinder SOHC 16-valve liquid-cooled gasoline |
| Total Displacement: 73.1 cu.in (1.19 L) |
| Rated Engine Power: 89 Hp (66 kW) at 6200 rpm |
| Fuel System Type: Multi-point electronic fuel injection |
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The Honda L12B is a 1.2-liter, naturally aspirated,
inline-four gasoline engine produced by Honda Motor Company. Introduced in 2008
as a successor to the L12A i-DSI (Intelligent Dual and Sequential Ignition), the
L12B represented a strategic shift within Honda’s L-series engine family. Its
primary objective was to harmonize the competing demands for higher specific
output and improved fuel economy, a balance achieved through the adoption of a
more sophisticated valvetrain. The engine is built on a lightweight, compact
architecture and served as the cornerstone powerplant for Honda’s global
subcompact and entry-level models for over a decade.
The L12B is distinguished by its implementation of Honda’s i-VTEC (Intelligent
Variable Valve Timing and Lift Electronic Control) system on a single overhead
camshaft (SOHC) layout. Departing from the earlier L12A’s
two-spark-plug-per-cylinder i-DSI design, which prioritized low-end torque and
ultra-lean burn, the L12B employs a conventional four-valve-per-cylinder
configuration with a single spark plug. This change allowed for higher peak
power and a more linear power delivery.
The engine features a “square” bore and stroke ratio, a chain-driven valvetrain
for reduced maintenance, and a high compression ratio. It was engineered to meet
increasingly stringent Euro 5 and Euro 6 emissions standards without the
complexity of direct injection in its primary iterations. The powerplant is
noted for its smooth operation, high-revving character, and robust reliability
when maintained correctly, though certain markets reported susceptibility to
intake carbon buildup from the Exhaust Gas Recirculation (EGR) system.
Engine Type: Inline-4, naturally aspirated, transverse mounting.
Displacement: 1,198 cc (73.1 cu.in).
Bore: 73.0 mm (2.87 in).
Stroke: 71.6 mm (2.82 in).
Compression Ratio: 10.2:1 (early variants, L12B1) to 10.8:1 (later variants,
L12B3/B4).
Engine Management System: Honda PGM-FI (Programmed Fuel Injection).
Ignition System: Electronic, direct ignition with coil-on-plug design.
Firing Order: 1-3-4-2.
Max Power: 66 kW (90 PS; 89 hp) @ 6,000-6,200 rpm.
Max Torque: 110-114 Nm (81-84 lb-ft) @ 4,800-4,900 rpm.
Redline: 6,500 rpm (fuel cut-off at approximately 6,800 rpm).
The cylinder block is constructed from open-deck,
high-pressure die-cast aluminum alloy with cast-iron cylinder liners. This
material choice minimizes overall engine weight while maintaining structural
rigidity and liner durability. The block integrates the upper crankcase and
features a deep-skirt design for increased rigidity against bending and
torsional forces.
The cylinder liners are centrifugally cast iron, providing a durable wear
surface for the pistons. The water jacket surrounding the cylinders is optimized
for uniform cooling, particularly around the exhaust ports and between the
cylinders. The block does not utilize a separate cylinder head gasket support
structure, relying instead on the precise mating of the aluminum block to the
aluminum head.
The cylinder head is a cross-flow, aluminum alloy
casting housing the SOHC i-VTEC valvetrain. This configuration operates four
valves per cylinder - two intake and two exhaust - actuated by roller rocker
arms. The i-VTEC system on the L12B functions by using a single camshaft with
two distinct profiles for the intake valves.
A hydraulically actuated locking pin selects the low-lift, low-duration profile
for normal driving or the high-lift, high-duration profile for increased power
output at higher engine speeds. The exhaust valves utilize a single, non-VTEC
profile but are integrated into the system for Variable Timing Control (VTC) on
the camshaft sprocket.
Valves: 16 total (8 intake, 8 exhaust).
Intake Valve Diameter: 28.0 mm (1.10 in).
Exhaust Valve Diameter: 24.0 mm (0.94 in).
Valve Stem Diameter: 5.5 mm (0.22 in) for both intake and exhaust.
Valve Seat Material: Sintered alloy for intake; high-strength alloy for exhaust.
The VTC (Variable Timing Control) actuator is mounted on the intake camshaft
sprocket, allowing continuous, non-VTEC-related phase adjustment of the intake
camshaft across a range of approximately 40 degrees. This dual strategy - VTEC
for lift/duration and VTC for phasing - optimizes volumetric efficiency across
the entire rev range. The cylinder head also incorporates the exhaust manifold
in some castings, a design feature that reduces weight and accelerates catalyst
light-off for emissions compliance.
The L12B employs a PGM-FI multi-point fuel injection
(MPI) system. Fuel is delivered via a returnless system, where the fuel pressure
regulator is located within the fuel tank assembly, reducing fuel vaporization
in the engine bay. Four high-impedance fuel injectors are mounted in the intake
manifold runners, positioned to spray directly onto the back of the intake
valves. This port injection design aids in valve cooling and carbon deposit
management, though it does not entirely mitigate EGR-related buildup.
The fuel system operates at a nominal pressure of 3.5 bar (50.8 psi) relative to
manifold vacuum. The system utilizes sequential injection, where each injector
fires once per cycle in time with its respective intake valve opening. This
precise control, managed by the engine control unit (ECU) in conjunction with
inputs from the air flow meter, oxygen sensors, and knock sensor, ensures
optimal air-fuel ratio under all operating conditions.
The lubrication system is a fully pressurized, wet-sump
design. A gear-type oil pump, driven directly by the crankshaft, is housed
within the aluminum front cover. The pump draws oil from the sump through a
screened pickup tube. The system incorporates a full-flow, spin-on oil filter
with an integral bypass valve, located on the rear of the engine block.
Oil is distributed through main galleries drilled into the cylinder block and
cylinder head, feeding the crankshaft main bearings, connecting rod bearings,
camshaft journals, and the i-VTEC hydraulic control solenoids. The system is
engineered to maintain stable oil pressure to the VTEC spool valve, which is
critical for the high-lift camshaft profile engagement.
Oil Capacity (including filter): 3.6 liters (3.8 US qt).
Oil Pressure at 3,000 rpm: 350-500 kPa (50.8-72.5 psi).
Oil Viscosity: 0W-20 or 5W-30 fully synthetic, API SN or ILSAC GF-5/GF-6.
Oil Pump Type: Rotor-type internal gear.
The cooling system is a sealed, pressurized,
thermosiphon design with a water pump driven by the engine’s serpentine
accessory belt. The pump circulates coolant through the cylinder block, cylinder
head, and a tube-and-fin radiator. A wax-type thermostat located in the water
pump housing regulates coolant flow, maintaining engine operating temperature
between 82-88 °C (180-190 °F).
The system employs a cross-flow radiator with an electric cooling fan controlled
by the ECU based on engine coolant temperature (ECT) sensor input and air
conditioning system demand. The cylinder head incorporates an integrated coolant
passage arrangement that prioritizes flow to the exhaust valve bridge areas,
which are the hottest points in the combustion chamber. Coolant capacity for the
engine and heater core is approximately 4.5 liters (4.8 US qt).
| Intake and Exhaust Systems |
Intake System: A plastic, tuned-length intake manifold
with an integrated resonator chamber is used to smooth airflow and reduce
induction noise. The manifold is connected to an air cleaner housing containing
a pleated paper filter element.
Exhaust System: A stainless steel exhaust manifold (often integrated into the
cylinder head) routes gases to a close-coupled three-way catalytic converter. A
downstream secondary converter and a single muffler complete the system. An
Exhaust Gas Recirculation (EGR) system routes a portion of exhaust gas back to
the intake manifold through a cooled passage and an electronically controlled
EGR valve.
Ignition System: The ECU controls individual ignition
coils mounted directly over each spark plug. This coil-on-plug configuration
eliminates high-tension spark plug wires, improving ignition reliability and
reducing electromagnetic interference.
Emissions Control: The engine utilizes a three-way catalytic converter,
closed-loop air-fuel ratio control with a linear air-fuel (LAF) sensor, a
positive crankcase ventilation (PCV) system, and the aforementioned EGR system
to meet Euro 4, Euro 5, and subsequent emissions standards.
Overall Length: 535 mm (21.1 in).
Overall Width: 600 mm (23.6 in).
Overall Height: 620 mm (24.4 in).
Dry Weight (complete engine): 85 kg (187 lb) without accessories.
Dry Weight (complete engine): 92 kg (203 lb) with intake, exhaust, and
alternator.
Valve Clearance (Intake): 0.18-0.22 mm (0.007-0.009 in)
when engine is cold. Valve Clearance (Exhaust): 0.23-0.27 mm (0.009-0.011 in)
when engine is cold. Inspection Interval for Valve Clearance: Every
40,000-50,000 km (25,000-30,000 mi). Adjustment requires shim replacement under
the roller rocker arms. Spark Plug Type: NGK IZFR6K-11 or DENSO SKJ20DR-M11
(iridium-tipped). Spark Plug Gap: 1.0-1.1 mm (0.039-0.043 in). Spark Plug
Replacement Interval: 100,000 km (62,000 mi).
Engine Oil Change Interval: 10,000 km (6,200 mi) or 12 months with synthetic
oil. Oil Filter Replacement: With every oil change. Timing Chain Inspection:
First inspection at 150,000 km (93,000 mi); no regular replacement schedule
unless noise or fault is detected. Coolant Replacement Interval: 120,000 km
(75,000 mi) or 10 years, then every 60,000 km (37,000 mi) thereafter. Drive Belt
(Serpentine) Inspection: Every 20,000 km (12,400 mi) for cracks and tension.
Cylinder Head Bolts (Step 1): 29 Nm (21 lb-ft)
Cylinder Head Bolts (Step 2): 90° (quarter turn)
Cylinder Head Bolts (Step 3): 90° (quarter turn)
Connecting Rod Cap Bolts (Step 1): 14 Nm (10 lb-ft)
Connecting Rod Cap Bolts (Step 2): 45° rotation
Main Bearing Cap Bolts (Step 1): 29 Nm (21 lb-ft)
Main Bearing Cap Bolts (Step 2): 45° rotation
Camshaft Bearing Cap Bolts: 22 Nm (16 lb-ft)
Intake Manifold Bolts: 22 Nm (16 lb-ft)
Exhaust Manifold Nuts: 27 Nm (20 lb-ft)
Spark Plugs: 18 Nm (13 lb-ft)
Oil Filter: 12 Nm (9 lb-ft) or 3/4 turn after gasket contact
Oil Drain Plug: 40 Nm (30 lb-ft)
Crankshaft Pulley Bolt: 181 Nm (133 lb-ft)
Flywheel/Flexplate Bolts: 98 Nm (72 lb-ft)
The Honda L12B engine was utilized across a range of
global and regional Honda models from 2008 onward, with variant codes indicating
specific tuning and emissions equipment.
Honda Jazz (2nd Generation, GE8): European markets (L12B1, L12B2). This variant
featured the 10.2:1 compression ratio and was tuned for Euro 5 compliance.
Honda Jazz (3rd Generation, GK5): European and certain Asian markets (L12B4).
This later variant incorporated “Earth Dreams” technology principles, including
lower-friction internal components and a revised 10.8:1 compression ratio.
Honda Brio (DD1): Southeast Asian markets (Thailand, Indonesia) and India
(L12B3, L12B4). This application was tuned for a broader torque curve suited for
urban driving, with power output adjusted for local fuel grades.
Honda City (4th Generation, GM4/GM6): Markets including Pakistan, India, and the
Philippines. The L12B served as the base engine for this sedan, often paired
with either a 5-speed manual or a CVT (Continuously Variable Transmission).
Honda Fit: The Japanese domestic market version of the Jazz used the L12B in
base “1.2L” configurations, though the 1.3L L13B was more common; the L12B was
designated for specific entry-level trims and fleet sales.
Honda Amaze: The first-generation compact sedan for the Indian market utilized
the L12B in its petrol variants, sharing its powertrain architecture with the
Brio.
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